Biological Psychology

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Animal Intelligence

Introduction to Animal Intelligence

  • Darwin (1859):
    - On the origin of species by natural selection.
    - Travelled to the Galapagos island where he came up with the theory of evolution to explain why there are many different species with different abilities and adaptations.

  • Romanes (1880s):- Was influenced by Darwins theory and stated there was a progressive increase in intelligence going up the evolutionary scale (insects to birds to apes).
    - However, this statement was not justified theoretically and so he went to test this.
    - He observed his dog open the latch on a gate and asked many people to send their reports of pets opening latches and more people sent in reports of their cats doing it than dogs.
    - Therefore, he concluded cats were more intelligent than dogs. But his experimental procedure was unsystematic as there may have been more cats in the environment.
    - He also assumed the animals had learned to remove the latch from the gate by imitating humans (rational imitation - which "involves a rational understanding of mechanical properties and considerable reasoning power"). He was also uncritical of his work.

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Animal Intelligence

Introduction to Animal Intelligence

  • Lloyd Morgan (1890s):
    - Was a zoologist/biologist who focused on Romanes work and claimed he was guilty of anthropomorphism (when we project human characteristics onto animals).
    - He suggested that if there are 2 explanations of behaviour, we must focus on the simplest explanation and only when we discredit that must we go on to study the most complicated one.
    - He thought Romanes should do experiments and observations to test his theory. So, he threw a stick over some railings and the dog went through them to fetch it, but on the way back he got stuck holding the stick horizontally in his mouth. He also found that the dog lifted the latch of a gate with the back of his neck not his snout.

  • Thorndike (1898):- Used puzzle boxes with different ways of opening the exit door. Put a cat in one and they had to figure out how to escape to be rewarded with food. The cat would thrash around until they made the appropriate response and escape, so when the solution becomes clear there should be a sudden decrease in the time taken to escape each time they're placed in a box.
    - His recordings did not support this, but showed that rewarding them increased their response tendency. Therefore suggesting the Law of Effect (if a response leads to a satisfying outcome then it will be strengthened).
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Animal Intelligence

History of Animal Intelligence

  • John B. Watson (1878 - 1958):- Advocated the importance of learning. He argued Thorndike studied learning important to the evolution of behaviour and intelligence. He also believed all learning consists of the strengthening and weakening of S-R connections by presenting reward or punishments after a response has been made.
    - He founded the idea of Behaviourism and stated there is an inability to investigate the mental state of humans and animals, so we should study observable and measurable things.
    - He argued that humans evolved from animals, so studying learning in animals provides an insight into how humans learn.

  • B. F. Skinner (1904 - 1990):- Was also a behaviourist interested in how rewards and punishments influence behaviour. He invented the 'Skinner Box' where rats were placed and required to press a lever in order to get food. This reward resulted in a strengthened response.
    - He conditioned 2 responses: Response shaping, whenever the rat moved towards the lever they'd receive a food pellet and when they get progressively closer they'd receive more.
    Schedule of Reinforcement, when food only becomes available when the rat presses the lever at 30 second intervals so it begins to press it rapidly nearer to the time interval.
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Animal Intelligence

History of Animal Intelligence

  • Ivan Pavlov (1849 - 1936):
    - Was a Russian physiologist who studied conditioning learning. A dog was placed in straps to hold it still and a tube was attached to its mouth to record saliva production.
    - He would present the dog with a bell sound followed by food. After a few pairings, the dog would end up salivating when hearing the bell alone in anticipation of food. Therefore, it learned that the bell was a signal for food (Classical Conditioning).

    - For Pavlovian Conditioning, a biologically significant event such as the food (the unconditioned stimulus, US) is signalled by a neutral stimulus such as a tone (the conditioned stimulus, CS). The US will always elicit a response, such as eating (the unconditioned response, UR), but at first the CS will have no effect on behaviour.
    - After a number of pairings of the CS and the US, a response such as salivation (the conditioned response, CR) will be performed during the CS. The CR provides evidence of learning about the relationship between the CS and US, and the strength of this learning is reflected by the strength of the CR.
    - If the CS should be repeatedly presented by itself, the strength of the CR will weaken and thus demonstrate extinction (no. drops of saliva decreases rapidly). A CR that is elicited by one stimulus may also be elicited by similar stimuli which demonstrates stimulus generalisation (i.e. different frequency of the bell tone).

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Animal Intelligence

History of Animal Intelligence

  • Rachman, S.J. (1966):
    - Investigated the reasoning behind fetishism, which is when a person gets aroused from handling an inanimate object.
    - He took volunteers and paired a leather boot with their arousal by showing them a picture of a naked woman and then making them hold the boot. Responses were measured using a penile plethsymograph.
    - After a number of pairings, the boot alone resulted in a response. This demonstrates that perhaps fetishism is due to the accidental conditioning with that object.
    - They were also given different types of shoes and a slight response was produced, with the shoe type less similar to a leather boot producing the lowest response (stimulus generalization).
    - Then finally they underwent a period of extinction.
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Animal Intelligence

Distribution of Animal Intelligence

  • Banks & Flora (1977):
    - Created a ranking of animal intelligence on a 10 point scale with fish being the least intelligent and humans being the most. There are different justifictions for this ranking:
    1. Appearance - If an animal looks intelligent then we are more likely to assume it is intelligent.
    2. The Great Chain of Being - Since Aristotle, attempts have been made to order all living creatures into a single sequence (a phylogenetic scale), and the position of an animal on that scale may be seen as an indicator of intelligence.
    3. Evolution - A sequence could be constructed to demonstrate the order in which animals appeared on the planet and assume that this correspnds with the progressive evolution of intelligence. However, evolution only explains the diversity of animals and does not allow us to rank them in a linear scale.
    4. Brain Size - The brain is responsible for intelligence and thus the size of an animals brain must indicate its intelligence. Jerrison (1973) pointed out that it is the size of the brain relative to the size of the body that is most likely to determine intelligence (cephalisation index).
     - Where K (c.i) = E (brain weight) / p (body weight) to the power of 2/3. However the cephalisation index does not prove how intelligent an animal is. So there is no compelling reason to believe intelligence is distributed throughout the animal kingdom in this manner.
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Animal Intelligence

Distribution of Animal Intelligence

  • For much of the last century, animal intelligence was regarded as being synonymous with the ability to learn. For example, if an animal was deemed to be intelligent then it was supposed to be a quick learner (i.e. it can quickly adapt to a new environment).

  • Learning is defined as: a relatively permanent change in behaviour that results from experience, and it can be studied using two techniques.
     - Operant (Instrumental) Conditioning: When an animal learns to produce a particular response in order to get food.
     - Classical (Pavlovian) Conditioning: When an animal learns that a particular stimulus leads to food being given.

  • However, there are problems with studies that have used these techniques to measure the speed of learning which show that it is not a useful tool for measuring animal intelligence.
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Animal Intelligence

Distribution of Animal Intelligence

  • Unexpected results between species:
    - Different species live in different environments which makes it difficult to give 2 species a speed of learning test that is equivalent for both.
    - Skard (1950) trained rats to run through a maze to get to the middle and get fod. The rats became adapted and learned not to make mistakes. It was found that the amount of training taken for rats to learn this is the same as humans.
    - Angermeier (1984) used operant conditioning to test the speed of learning in various species. He used different tasks to suit the different species, e.g. fish had to push a rod and rats had to pull a lever. He found that fish were the quickest and human infants were slowest.

  • Bitterman (1975):- Suggested there are obstacles to overcome in order to successfully test the speed of learning in different species, i.e. equating the perceptual demands of the task so that all the relevant cues are equally salient for both species, also to equate the motivational demands of the two tasks so that both species are equally willing to engage in the test.
    - He suggests these variables can be overcome by a method of 'systematic variation'. However, this is time consuming, inefficient and rarely used.
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Animal Intelligence

Distribution of Animal Intelligence

  • Unexpected results within species:
    - A given species tends to learn some things quickly and other things slowly. For example, Pearce, Colwill & Hall (1978) found it easy to train rats to press a lever for food but difficult to train them to scratch themselves for the same reward.

  • Garcia and Koelling (1966):- Demonstrated that rats quickly learned that a flavour (of saline solution) signals illness, but they had difficulty learning that the same flavour signals a foot shock.
    - Conversely the rats learned quickly when a compound of light and a tone together signalled a shock, but slowly when the same compound signalled illness.
    - If speed of leaning is our measure of intelligence, it is impossible to conclude from these results whether rats are bright or dim.
    - One explanation for this pattern of results is that animals are disposed to learn about some relationships more readily than others. They appear to learn most readily about those relationships which they encounter naturally and are important for survival.
  • This conclusion has led researchers to propose that evolution results in the intelligence of animals being shaped by the environment in which they live. Therefore the intelligence of animals living in different environments will be different.
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Animal Memory

Animal Memory 1

  • Animal intelligence can be defined as a set of intellectual processes:
    - Memory
    - Learning
    - Reasoning
    - Navigation
    - Communication.

  • Defining memory: Memory is shown if something from a past experience affects an animals behaviour.
  • Vander Wall (1982):- Studied a bird known as 'Clarks nutcracker' which, during the summer, collected pine seeds in its crop then hid them in holes in the ground (caches).
    - During the Winter, they returned to these holes to retrieve the seeds, even if the location is covered in snow. It was found that they deposited 33000 pine seeds in 7000 caches and were able to remember 2500 - 3750 cache locations.
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Animal Memory

Animal Memory 1

  • Bob Cooks, Tufts University:- Investigated the capacity of pigeons memory over 24 months. They were shown different photos and had to peck left at certain images and peck on a key on the right to others in order to get a reward (food). It was found that out of 1200 photos, they were correctly able to respond to each, even with 20000 intervening photos.

  • Joel Fagot, Marseille:- Investigated the capacity of baboons memory over 6 months. They could correctly remember 5000 photos with 48000 intervening trials.

  • The ability to remember these photos is known as concrete thinking, which involves fcts and information in its most literal form.
    - Animals also seem to be capable of remembering quite abstract information, such as time and numbers, which is a level of thinking characterized by the ability to make and understand generalizations or relationships.
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Animal Memory

Animal Memory 1

  • Time:
    - Church & Deluty (1978)
    put rats into a conditioning chamber for an hour at a time and played a tone for either 4 seconds or 16 seconds.
    - When rats hear the 4 second tone they must push the left lever, and when they hear the 16 second tone they must push the lever on the right. Therefore, as they are able to do this task they are able to solve discriminations between lengths of time.
    - However, it has been argued that the animal moves more slowly around the chamber and accidentally ends up at the correct lever.

  • Number: - Von Osten & Pfungst (1908): Clever Hans was a horse trained by Von Osten that was taught to count by tapping his answer to questions on the ground. Pfungst tested the horses ability to do this and found that he would only answer in the presence of his trainer and when Von Osten also knew the answer.
    - It was found that Von Osten had adopted a particular gesture of tension and would relax once Hans had tapped to the correct number.
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Animal Memory

Animal Memory 1

  • Number:
    - Meck & Church (1983) placed a rat in a chamber and played either 2 pulses or 8 pulses of a sound and they would have to press the left lever for the short number and the right lever for the long. It was believed that the train of two pulses is shorter so the rats may be going by duration. Therefore, a test trial of 2 long pulses and 8 short showed they were still able to answer correct.

    - Brannon & Terrace (2000): Monkeys had to press buttons with the correct number of counters shown on it from 1-4 to match the number presented to them, and after learning this they were able to press the correct buttons after rearranging of the counters. However, they might be guessing by area so they were given different shaped and sized counters.

    - Pepperberg (1994): Trained Alex the grey parrot to talk and answer questions about the colour and shape of objects. Then he would be asked to answer how many green/blue etc objects there are presented to him. The 'Clever Hans effect' was suggested with this parrot as he would only work with Pepperberg in the room.

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Animal Memory

Animal Memory 1

  • Categories: - Humans have the capacity to acquire concepts (a mental representation of the characteristics of an item) and form categories, which allows a large number of different objects to be classified with the same label, e.g. a chair. As a result of ths ability we can correctly identify an object, even if we have never seen it before.

    - Herrnstein (1976): Pigeons were shown a series of photographs, half of which contained a tree. Pecking at a response key during photographs with a tree resulted in food being rewarded. The birds soon solved the discrimination and even in test trials with novel photographs. This study had implications for future research.
    - Language is not necessary for the formation of a category.
    - Categorisation may depend on learning about the significance of selected features of the training stimuli. It may also depend upon remembering individual photographs because animals are better at classifying familiar rather than novel photos.
    - New photographs would then be classified correctly on the basis of their similarity with the exemplars used for training. Animals might adopt a feature-based or exemplar-based strategy depending on how many exemplars are shown. It is believed these strategies may also be important for categorisation by humans.

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Animal Memory

Animal Memory 2

Short term memory refers to information that can be retrieved for only a relatively brief period of time after it has been acquired, whereas long-term memory refers to that which, once acquired, can be retrieved over long periods of time.

Short-Term Memory

  • Habituation:
    - A reduction in responsiveness to a stimulus as a result of its repeated presentation by itself.
    - Whitlow (1975) used a plethysmograph attached to the ear of a rabbit to measure the amount of blood flow. A tone (tone 1) was presented to the rabbit, which produced a strong startle response, then the same tone was presented 60 seconds later to produce a weaker startle response. This demonstrates habituation.

    - Wagners theory: When the tone is first presented, the animal is able to memorize that tone so when it is presented again the rabbit has a weaker response. This made Whitlow repeat the experiment with a 120 second gap instead, where the rabbit once again showed a strong startle response.

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Animal Memory

Animal Memory 2

  • Effector Fatigue:
    - One idea is that perhaps the nervous system was less responsive to the second tone because it was still recovering from the effort required to produce a strong startle response to the first.
    - Whitlow tested this explanation by presenting the rabbit with 2 different tones with an interval of 60 seconds. Wagners theory predicts that a strong startle response will be seen to the second tone because it will not match the memory of the first.
    - This prediction was confirmed, the results show that the effector system was fully capable of generating a strong startle response after 60 seconds and thus is it unlikely that Whitlows demonsration of habituation was due to effector fatigue.

  • Receptor Fatigue: - Another thought is that the receptors responsible for detecting the tone were so overwhelmed by the first tone that they failed to detect the second properly.
    - Whitlow presented the same tone twice, 60 seconds apart but introduced a brief distracting stimulus at 30 second intervals. A strong startle response was observed to the second presentation of the tone so the distractor is said to have resulted in dishabituation.
    - Therefore habituation without the distractor is unlikely to be due to receptor fatigue.
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Animal Memory

Animal Memory 2

  • Radial Maze: - Is another tool for studying short term memory. Normally this maze consists of 8 arms radiating outwards from a small centre arena. Food is placed in a trough at the end of each arm and the rat will start in the centre. They are allowed to explore the maze until the have retrieved all the food. An experienced rat will run down each arm just once to collect the food, which suggests that it keeps a record of the arms it has visited in order to behave efficiently.

    - Beatty & Shavalia (1980) showed that the memory of the arms that have been visited can last for 4 hours but it then becomes weaker. This result justifies the claim that the task involves STM.

    - Other experiments have shown that the memory for locations is determined by landmarks in the room, for example they see a statue at the end of one arm to know they have been there before.

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Animal Memory

Animal Memory 2

Long-Term Memory

- A number of researchers have argued that the effectiveness of LTM depends upon a consolidation process where it is learned from STM then retains information.

  • Hebb (1949):
    - Suggests that if an event is to be remembered accurately, and for a long period of time, then it must be followed by a consolidation process to allow the brain time to form a clear memory of the event.
    - Consolidation was assumed to be most effective if no distracting stimuli were presented after the training episode. In support of this claim it was found that a burst of electro-convulsive shock (ECS) after a training episode results in a poor memory for that episode.
    - ECS is given to people to alleviate depression, with loss of memory of the events leading up to the treatment as a side effect. ECS will inhibit the consolidation process that neurones have to fire together for a while.
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Animal Memory

Animal Memory 2

  • Duncan (1949):
    - Rats were placed in a black compartment and when the light comes on the rat would receive a foot shock after 10 seconds. They have to jump over into the white compartment to avoid shock.
    - Some rats would receive ECS as the jump over the barrier and these could no longer remember that the light turning on signals shock.
    - A prediction from certain consolidation theories of animal memory is that once a memory has been formed, it can be modified if the animal should experience a fraction of the original training episode. This effect is known as reconsolidation or reactivation.

  • Gordon et al (1979):
    - Demonstrated this effect by training rats to run from the white chamber to the black chamber of a shuttle box in order to avoid footshock. 3 different groups were then returned to the white chamber four days later and the time it took rats to run to the black chamber was recorded.
    - The groups were placed in the white chamber for 0 seconds, 15 seconds or 75 seconds on the day before the final test trial.
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Animal Memory

Animal Memory 2

- The groups that spent 0 or 75 seconds in the chamber were rather slow to escape to the black chamber, whereas the group with 15 seconds of exposure to the white side escaped more rapidly.

- According to the consolidation theory, 15 seconds of exposure allows the memory of the original training to be reactivated, and thus become more effective through a period of additional consolidation, even though shock was not presented during this period.

- A similar effect might also be expected in the group that received 75 seconds of exposure. The prolonged absence of shock during this period was assumed to allow animals to modify their memory of the white chamber by allowing them to appreciate that shock was now less likely to occur in it than during the original training.

- Considerable interest is now being shown in the mechanisms that are responsible for reconsolidation effects.

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Associative Learning

Associative Learning

Associative learning refers to the change in behaviour that occurs when an animal repeatedly experiences two events paired together. The classic demonstration of associative learning is provided by Pavlovian conditioning. Any analysis of learning must answer three questions: What is learned? What are the conditions for learning? How is learning translated into behaviour?

  • What Is Learned?
    - According to one point of view, presenting a CS activates a centre in the brain which is responsible for the perception of this stimulus, and presenting an US activates another centre, which is responsible for both the perception of this stimulus and generating a response.
    - Pairing a CS and US is assumed to result in the formation of a connection or association between the two centres so that a subsequent presentation of the CS will excite the CS centre which, in turn, will excite the US centre and elicit a response. Support for this proposal can be found in an experiment by Colwill and Motzkin (1994).
    - A single group of rats first received appetitive conditioning in which a tone signalled food pellets and a light signalled sucrose solution. Both stimuli elicited a response (CR) of approach to the food dispenser. The rats then received daily sessions in which the consumption of food pellets was followed by an injection of LiCl (a poison). They were also allowed to consume sucrose solution in separate sessions without adverse consequence.
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Associative Learning

Associative Learning

  • What Is Learned?
    - This training resulted in the rats willingly consuming the sucrose, and rejecting the food pellets. During a final test session in which the tone and light were presented without food or sucrose, a strong CR was observed during the light, but not the tone.
    - The explanation for this outcome is that the tone excited a representation of food and because food was no longer attractive, there was no point in the rats heading to the food dispenser.

  • Translation to Behaviour:- A variety of factors determine the influence of associative learning on behaviour. One important function of the conditioned response is that it prepares the animals for the impending unconditioned stimulus. In some cases the CR counteracts, or compensates for the effects of the US. Thus the saliva elicited by a tone that signals food for a dog might counteract the dry mouth that will result from eating the food.
    - The suggestion that conditioned responses counteract the reaction to the unconditioned stimulus has important consequences for our understanding of the effects of drugs. Siegel has argued convincingly that the development of drug tolerance can be explained, in part, by referring to this influence of conditioned responses.
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Associative Learning

Associative Learning

  • Translation to Behaviour:- He suggested that the stimulation provided by the administration of the drug serves as the CS, which excites a CR that is opposite to the effect of the drug. As a consequence the drug will be maximally effective when it is first injected, but thereafter each injection will elicit a stronger and stronger conditioned response to oppose the effects of the drug. Siegel (1979) provided support for the analysis in an experiment using the drug morphine, which has an analgesic effect. Rats were first injected with morphine which lost its analgesic effect with repeated injections thus demonstrating the development of drug tolerance. He then gave repeated injections of saline.
    - The saline injections were intended to weaken, through extinction, the effects of the associations formed during the initial training; that is, the associations formed between the sensations produced by the injection process and the effects of the drug itself.
    - As a result, the stimulation provided by the injection routine should no longer excite a CR that would compensate for the analgesic influence of the morphine. In support of this analysis, Siegel found that subsequent injections of morphine resulted in a stronger analgesic effect than was observed at the end of the initial treatment. Timberlake and Grant (1975) have shown that if the appearance of one rat signals the delivery of food to another rat then the latter will direct social responses towards the former. This shows that conditioned responses are not always made in preparation for the delivery of the US.
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Associative Learning

Associative Learning

  • Conditions of Learning:Contiguity: A long standing claim was that the mere pairing of one event with another was sufficient for associative learning to take place. The results from a variety of experiments have challenged this claim.

    Surprise: An experiment by Kamin (1969) demonstrating an effect called blocking posed a serious challenge to the principle of contiguity. An experimental group received a noise as a signal for shock. The same group then received a light presented simultaneously with the same noise as a signal for the same shock.
    - Finally, the light was presented by itself. Even though the light had repeatedly been pairing with shock, it failed to elicit a substantial CR. A control group just received the light and noise presented together as a signal for shock, and showed a substantial CR to the light when it was presented alone. Thus the initial pairings of the noise and shock prevented or blocked learning about the relationship between the light and shock in the experimental group, so that learning about the relationship between the light and shock would not take place.
    - Rescorla & Wagner (1972) developed a formal theory of the importance of surprise in associative learning. This is one of the most important theories of the last century.

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Associative Learning

Associative Learning

  • Conditions of Learning:- To test his notion about surprise, Kamin repeated the treatment given to the experimental group, except that a small shock followed the noise by itself, and a larger shock followed the noise-light compound. The large shock would come as a surprise and provide the necessary condition for learning about the light-shock relationship. This prediction was confirmed.

    Attention: Learning that a stimulus signals food, say, will progress slowly if the stimulus is repeatedly presented by itself before it is paired with food. This disrupted in conditioning is referred to as latent inhibition. One explanation for this outcome is that animals cease to pay attention to the neutral stimulus when it is presented by itself, and thus fail to learn about it when it is paired with the US.
    - There are 3 different theories concerning the factors that determine whether or not animals will pay attention to a stimulus. In brief, the theories are as follows:
    - Mackintosh (1976) has argued that animals will attend to a stimulus if signals an event of importance. If it signals nothing of importance, then it will be ignored.
    - Wagner (1981) has argued that animals will attend to a stimulus if it is novel, and ignore it if they are familiar with it.

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Associative Learning

Associative Learning

  • Conditions of Learning:
    Attention: Pearce & Hall (1980) proposed that animals attend to a stimulus if they do not know what it predicts, and therefore further learning about it is required; and they will ignore a stimulus if they know what it predicts and no further learning is required. They further suggested that there are two sorts of attention, one necessary for learning (controlled processing) and the other necessary for performance (automatic processing).
    - An experiment by Kaye & Pearce (1984) evaluated these different theories. It made use of the fact that rats will direct an orienting response (OR) to a localised light bulb in a dark chamber when it is novel. This response was used as an index of the amount of attention paid to the light. Group L- just received the light presented by itself for 10 seconds at a time once every five minuets or so. The OR to the light declined with repeated exposure. All three theories predict this outcome.
    - Group L+ was treated in the same way as Group L-, except that every presentation of the light was followed by food. The OR to the light declined with repeated trials, but more slowly than in Group L-. This result can be explained by W, P&C but not M.
    - Group L+/- was treated in the same way as the other 2 groups, except that food was presented unpredictably after the light on 50% of trials. The OR to light was sustained over many trials.
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Associative Learning

Associative Learning

  • Conditions of Learning:

    Observational Conditioning
    - Observational conditioning refers to associative learning that takes place through watching the behaviour of another animal. An example in the laboratory is provided by the work of Mineka and Cook. An observer monkey watched a demonstrator show fear in the presence of a snake. Although the observer was initially unaffected by snakes, this episode resulted in the observer displaying fear during a subsequent encounter with a snake. Although the observer was initially unaffected by snakes, this episode resulted in the observer displaying fear during a subsequent encounter with a snake.
    - This change in behaviour by the observer is attributed to observational conditioning, where the snake is the CS and the fearful behaviour of the demonsrator is the US.
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Animal Problem Solving

Animal Problem Solving

Problem solving takes place whenever an animal overcomes an obstacle to obtain a goal. Thorndike argued that animals solved problems solely through learning from trial and error, i.e. they behave by random to accidentally solve a problem then contnue producing that response.
- As an alternative, it is possible that animals solve problems through reasoning. Reasoning is said to occur when two items of information, or premises, are combined to draw a novel conclusion.
- If the conclusion necessarily follows from the premises on which it is based, the reasoning is referred to as deductive; if the conclusion is likely to follow from the premises (i.e. is not exactly correct), it is referred to as inductive.
- Animals have been shown to solve problems in a variety of ways where their behaviour cannot be explained simply in terms of trial and error processes.

  • Navigation:
    - Most animals live in nests or burrows and whe they have been out foraging, how do they get back home?
    - Wehner & Srinivasan (1981): Found that ants will forage in a haphazard fashion for food and when they have found it they are able to return directly to their nest. Here, the problem for the animals is to know how far it must travel and in what direction for the return journey.
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Animal Problem Solving

Animal Problem Solving

  • Navigation:- Navigation in these circumstances is referred to as dead-reckoning (keeping a record of the direction and distance they must travel), but we do not fully understand how it takes place. A rather different task involved taking them and releasing them 600m away from their nest after they had got their food. The ants continued back to their home as though they had not been moved showing that they do use dead reckoning. To prove the animals take note of how many steps they take they were given stilts and so they went too far as their strides were longer.

    - A simple example has been provided by Cartwright and Collett (1983) with gerbils who are able to find food that is hidden at a certain distance and direction from a given landmark. Navigation in these circumstances is referred to as piloting.

    - A more complex example of navigation comes from studies of rats in a circular swimming pool containing a submerged platform and landmarks outside the pool by Morris (1981). 3 groups (control, same platform place, new platform place). It was suggested they refer to a cognitive map but was found that they didnt get lost when put in a different shaped pool so they learned to pilot by swimming on the right hand end of a long wall.

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Animal Problem Solving

Animal Problem Solving

  • Insight:
    - In the early years of the last century a group of Germans developed the Gestalt school of psychology. One feature of this school was the belief that problems were solved by suddenly seeing them in a different way.
    - The term insight was used to explain this sudden solution to a problem. A prominent Gestalt psychologist Kohler (1925) conducted experiments to demonstrate insight in chimpanzees. He believed problem solving is a sophisticated skill where the solution suddenly comes to you after struggling to find it.
    - In one study, a chimpanzee was required to retrieve a banana from the ceiling of its cage. After pacing up and down Soltan suddenly moved some boxes so that they were underneath the banana and, using them as a platform, the chimpanzee was able to reach its goal.
    - The goal directed nature of this activity suggests the problem was not solved by trial and error, and the sudden change in the animals behaviour from pacing up and down to moving the boxes indicated to Kohler the solution was arrived at by insight.
    - This interpretation has been criticised, because the problem solving behaviour is observed only in chimpanzees with experience of moving boxes etc. Perhaps the solution to the problem arose as a result of trial and error in the past.
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Animal Problem Solving

Animal Problem Solving

- More recent demonstratons of insight have been obtained with pigeons, and New Caledonian crows. Pigeons were placed in an arena and had to move a box towards a dot on the ground to get food. They were trained to stand on the box and peck at a plastic banana to get their reward. In the test trial they had to move this box underneath the banana and stand on it to reach the banana to peck at it. Each subject was confused at first but then suddenly appeared to figure out the solution.

  • Analogical Reasoning:- An example of inductive reasoning is by solving problems through analogy: e.g. a cow is to a calf as a cat is to a kitten etc.
    - An experiment by Gillan and Premack (1981) explores an animals ability to comprehend relationships. They provided a demonstration of analogical reasoning in a chimpanzee, Sarah, who had been trained to communicate with her trainers with linguistic symbols. The ability to solve analogies is important because it may reflect a capacity for abstract thought.
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Communication and Language

Communication and Language

Communication can be said to take place when one organism transmits a signal that another organism responds to appropriately.

One example of animal communication is provided by the honey bee studied by von Frisch. When the bees return to their hive with honey they engage in a dance in order to tell other bees about the location of food.
- The round dance shows food is 10-100m from the hive (i.e. nearby) whereas a waggle dance indicates the direction and distance of food from the hive. The rate at which the bees abdomen waggles is the distance from the hive where the food is. The angle tells the observer which direction to go.

Seyfarth & Cheney studied Vervet monkeys which live in colonies and make alarm calls of a particular sound to tell the others about what predator is present out of a snake, a leopard and an eagle. On hearing these sounds, other members of the troupe then react appropriately by either looking down at a snake, fleeing to the trees from a leopard or looking up at an eagle.

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Communication and Language

Communication and Language

  • Language:
    There is no doubt that many different animals communicate, and in many different ways. But can these acts of communication be regarded as being equivalent to what many regard as the pinnacle of human intellectual development, languageChomsky stated that humans have an innate LAD essential to acquire language An act of communication is often regarded as language if it meets a set of criteria (known as Hocketts criteria), of which the following are most important:

- It must be composed of discrete units (e.g. words or different sounds by monkeys)
- The units must be meaningful and arbitrary (i.e. the meaning of the words can be flexible).
- Communication about events that are displaced in space and time must be possible (i.e. you can discuss something that is not in the immediate present, e.g. honey bees communicate about where the food is located without it being in the vacinity)
- The units of communication must be combined according to the rules of grammar or syntax.

Natural acts of communication by animals fulfil the first 3 of these criteria, but not the last one. Moreover, there is no indication from the behaviour of animals that their communications match the sophistication of language.

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Communication and Language

Communication and Language

It is thought that perhaps animals could be taught language.

Hayes & Hayes (1961) encouraged a chimpanzee to say a few words including mama, papa, cup and up. However it could not learn any more and the limited success of animal language studies is thought to be a consequence of the inability of animals to make the correct speech sounds.

Gardner & Gardner (1969)overcame this obstacle by teaching Washoe, another chimpanzee, American Sign Language. She mastered 130 words and could understand and create small sentences with these words. It was found that she managed to create novel sentences to prove her understanding.

Premack (1971) taught another chimpanzee, Sarah, to communicate using plastic tokens arranged into grammatically correct sequences. If the symbols were arranged to mean 'put apple on plate and banana in pail' then it was argued that she understood grammar as she could do the action.

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Communication and Language

Communication and Language

Rumbaugh (1977) taught Lana (an adult chimpanzee), Austin and Sherman (teen chimpanzees) to communicate by pressing tokens on a computer keyboard. These studies were based on the principles of instrumental (operant) conditioning.

Rumbaugh & Savage-Rumbaugh (1994) taught Kanzi, a young pygmy/bonobo chimpanzee with a computer keyboard that he had learned to use from observing his mother Matuta, but they also spoke to him in English. After several years he began to show signs of understanding complex spoken sentences.

In terms of Hocketts criteria, these studies demonstrate that the chimpanzees were able to communicate with signs or symbols that were discrete units, and arbitrarily related to what they signified. At least some studies demonstrated that chimpanzees understood the meaning of the units of communication. There was also evidence that the chimpanzees were able to understand communications about events that were displaced in time and space (e.g. Kanzi was able to get pine needles from the fridge).

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Communication and Language

Communication and Language

The main controversy concerns the issue of whether the acts of communication in these studies were governed by rules of grammar. It was originally claimed that some of the spontaneous acts of communication by Washoe were structured according to the rules of syntax, but an important study by Terrace et al (1979) cast doubt on this conclusion.

He taught a chimpanzee called Noam Chimpsky (Nim) to use sign language an raised him from birth. This found that of 19000 utterances of 5000 different types, there was no evidence that the chimp used grammar.

At present, there is little evidence to suggest any animal can create a sentence according to grammatical rules. Work with Kanzi, and dolphins, hints that animals may be able to understand novel sentences. However, language or at least the ability to create sentences may be the major difference between the intelligence of humans and animals.

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Brain Structure and Methods

Brain Structure and Methods

Phineas Gage was a famous case of brain damage in which he was a stable hardworking foreman until he suffered severe brain damage. A large metal rod was exploded back into his skull through the frontal lobe of his brain. He recovered quickly but his personality had changed and he was now rude, lazy and indecisive.

  • Brain and Behaviour:
    It is very difficult to study the brain as it has 10-15 billion neurones and even more synapses. Thus it is a debate as to how the brain might control behaviour.

    Descartes believed that animals acted as biological mechanical devices with the muscles etc controlled by the brain and nerves. He suggested humans differ from animals in that they have a non-material soul which interacted with the body via the pineal gland. The challenge for modern neuroscience is to explain human behaviour purely in terms of the interaction of the brain or body with the environment, and assuming that everything is physical and there is no soul.

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Brain Structure and Methods

Brain Structure and Methods

The concept of emergence:
- One molecule of water is not wet but many together are; No one instrument in an orchestra can produce a symphony but together they do etc. In the same way that no one neurone produces consciousness.

In relation to Phineas Gage, other people with damage to the same regions of the frontal lobes displays similar patterns of behavioural chanes and this is true for other brain regions too.
- Damage to the medial temporal lobe causes memory problems (e.g. Amnesia)
- Damage to the parietal cortex can result in attention problems (e.g. Visual neglect)
- Damage to the occipital cortex can cause various kinds of visual perception problems (e.g. Akinetopsia - aka motion blindness, caused by disruption to the dorsal stream)

These findings indicate that brain regions are specialised for different cognitive and perceptual tasks, and suggest that there is a consistent correspondence between where brain activity will be when mental activity occurs.

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Brain Structure and Methods

Brain Structure and Methods

  • Localisation:
    -
    Muller's Doctrine of Specific Nerve Energies
    states that the information carries by nerves depends on the location of the nerve and what it connect to, not the nature of the signal. This explains how different sorts of information is transmitted despite the fact that the signal (i.e. action potential) is essentially the same in all neurones. A good example of this is the separation of the different sensory pathways.

    - Olfactory pathways from the nose project directly to the cortex; equilibrium pathways project to the cerebellum with a branch to the cortex via the thalamus. All other pathways pass through the thalamus before they project to their relevant cortical area.

    - Connections in the brain are organised in a topographic manner (e.g. there is a point-to-point correspondence with some aspect of the body). For example, the somatosensory cortex (behind the central sulcus) reflects a map of the body's somatic senses. Interestingly, the amount of cortex devoted to each region of the body depends on how sensitive to touch it is (i.e. how highly innervated it is) not how large it is. e.g. Sensory Homunculus.

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Brain Structure and Methods

Brain Structure and Methods

  • Sub-Cortical Structures:The outer section of the brain is called the cerebral cortex. It is divided into 4 lobes (frontal, temporal, parietal and occipital). The human cortex is very convoluted which greatly increases its surface area. The convolutions are called sulci (small grooves), fissures (large grooves) and gyri (the bulges between the grooves).

    - The subcortical brain is also divided into a number of different structures. Important structures include the corpus callosum (bundle of commissural fissures connecting the two cerebral hemispheres), the hypothalamus (involved in feeding and other functions), and many more.

    - The basal ganglia are subcortical structures which are important for the control of movement. There are three main dopaminergic systems in the brain, the nigrostriatal (from the substantia nigra to the corpus striatum), the mesolimbic (from the midbrain to the limbic system) and the mesocortical (from the midbrain to the cortex).

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Brain Structure and Methods

Brain Structure and Methods

  • Sub-Cortical Structures:- There are two pathways involving the basal ganglia, the direct pathway which results in the activation/excitation of movement, and the indirect pathway which results in the suppression of movement.
    - Parkinson's is caused by the degeneration of neurones in the substantia nigra, preventing the release of dopamine onto the corpus striatum via the nigrostriatal pathway. This results in the inhibition of the direct pathway and thus the suppression of movement. The symptoms of this disorder include tremors, rigidity and slow movement but there are also cognitive dysfunctions such as memory loss and depression. One treatment of Parkinsons is to use L-Dopa along with an antagonist of L-Amino acid decarboxylase to allow the L-Dopa to cross the blood brain barrier before being converted into dopamine. The effectiveness of this treatment however decreases over time.
    - Another treatment involves destroying part of the basal ganglia, such as the Global Pallidus internal. As this part is inhibitory to the thalamus, removing it would result in less inhibition of the thalamus so there is more excitation of the motor cortex.
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Brain Structure and Methods

Brain Structure and Methods

  • Sub-Cortical Components:The connection of the basal ganglia:
    - In the direct pathway the motor cortex excites the striatum to inhibit the GPi from inhibiting the thalamus, and thus the thalamus is able to excite the motor cortex producing movement.
    - In the indirect pathway the motor cortex excites the striatum to inhibit the GPe to prevent the inhibition of the subthalamic nucleus, thus the STN is able to excite the GPi to inhibit the thalamus so there is less excitation of the motor cortex.

    Cytoarchitecture:
    - Different brain regions have different cell types in different arrangements or frequency. This is described as cytoarchitecture which allows for the definition or recognition of discrete areas in the brain.
    - An identifiable group of cell bodies is called a nucleus. Cytoarchitecture allows for division of brain areas. This is useful because these divisions may be functional and allows different people to examine the same region.

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Brain Structure and Methods

Brain Structure and Methods

  • Cytoarchitecture:- The most powerful anatomical tools rely on axonal tracers which require live brains. Thus the knowledge of human connections is relatively poor. Much investigation of human neuroscience from analogy to the brains of other animals from squids to apes.
    - The human brain is not unique: There are no uniquely human brain cells although there is atleast one type of cell that is only found in the cingulate cortex of great apes and humans;
    The message system of action potentials is also the same in all brains; Asymmetry of the hemispheres is also seen amongst songbirds and great apes; and the component structures of the human brain are also seen in others.

    - However, there are also many differences between the brains of different species, e.g. the relative size of different parts of the brain differ (the human has a large neocortex, rat has larger olfactory cortex) and the overall shapes vary.
    - The similarities mean it is possible to draw analogies from the brains of other animals to our own while the differences mean that great care must be taken when doing so.
    - The fact that many techniques for investigating the brain cause it irreparable damage means that much of the work in neuroscience is done on the brains of animal other than humans.

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Brain Structure and Methods

Brain Structure and Methods

  • Information Transmission:- Electrochemical processes provide the means for information communication through the brain and synchronous electrical activity in networks of neurones leads the generation of electrical fields that travel through the brain and can be recorded outside the head using electroencephalograpy (EEG).
    - Event Related Potentials (ERPs) are discrete segments of the EEG, time-locked to an event of interest. ERPs consist of a series of positive and negative deflections that each represent different aspects of cognitive processing: The P1 component indexes visual perception. It is larger for large than small stimuli, and larger for bright than dim stimuli. 
    - People were asked to attend to either the left or right side of a screen and stimuli were flashed on attended and unattended sides. P1 is larger when a stimulus is shown where people are attending. This finding is consistent with the view that the quality of our visual perception is influenced by our attention, an example of top-down control over behaviour.
    - ERPs are a direct index of neural activity in real time, but because they are recorded on the outside of the head it is difficult to be sure of exactly what brain regions are responsible. That is, ERPs have poor spatial resolution, but very good temporal resolution.
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Brain Structure and Methods

Brain Structure and Methods

  • Information Transmission:
    - Hemodynamic methods (in particular fMRI and PET) indirectly measures changes in blood flow resulting from neural activity. The signal is recorded from within the brain where it occurs. Relative to ERPs, fMRI has a good spatial resolution and poor temporal resolution. Thus, real time and hemodynamic measures have different strengths and weaknesses, and tell us different things about the relationships between brain activity and mental activity.

    - The fMRI data tells us something about location while the ERP data tells us something about how attention operates and also about the time course of brain activity.
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Brain Cells and Action Potentials

Brain Cells and Action Potentials

  • Structure of a Neuron:- It involves dendrites protuding from the soma, and an axon hillock forming the axon on the other side. The axon is surrounded by myelin sheath which contains nodes of Ranvier where depolarisation occurs, and ends up at synaptic terminals. There are many different types of neurones, but all variations follow the basic plan. Information generally flows from dendrites along the axon to other nerves, across the synapses, or to muscles and organs etc.
    - Types include pyramidal projection neurones (with their cell body shaped as a pyramid) located in the rat hippocampus, and Purkinje cells found in the cerebellum with many dendritic protusions and a large cell body.

    - The brain is not just composed of neurones, there are also very important supporting cells known as neuroglia. There are 10-50 times as many glial cells than neurones and they do not carry nerve impulses but have many important functions.
    Astrocytes - Are star shaped cells that provide physical and nutritional support for neurons, clean up brain debris, transport nutrients to neurones, hold neurones in place, digest parts of deadneurones and regulate the content of extracellular space.

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Brain Cells and Action Potentials

Brain Cells and Action Potentials

Microglia - Digest parts of dead neurons and have some immune system function.
Oligodendroglia - Provide the insulation (myelin) to neurones in the central nervous system, whereas Schwann cells perform this function outside the CNS.

White and Grey Matter:
- Where cell bodies predominate the cortex has a greyish appearance and is known as grey matter. There the myelinated axons predominate (e.g. in tracts) the cortex has an opaque white appearance known as white matter.

  • Nerve Signals:
    - The chemical basis involves ions both inside and outside the neurones. The key ions are Na+, K+ and Cl-, plus large organic negative ions (A-). The membrane acts as a barrier but has ion channels through which some ions can pass.
    - At resting membrane potential, the inside of a neuron is more negatively charged than the outside (-70mV), due to leak potassium channels through which positively charged K+ ions exit the cell.
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Brain Cells and Action Potentials

Brain Cells and Action Potentials

  • Resting Membrane Potential: - Is produced and maintained by a variety of factors:
    such as concentration gradient - because ions move randomly they tend to move away from an area of high concentration to areas of lower concentration;
    Electrostatic forces - like charges repel and opposite charges attract. Thus the ions tend to move to equalise overall charge;
    Differential membrane permeability - When neurones are at rest the membrane is totally resistant to the passage of organic ions, extremely resistant to the passage of sodium ions, moderately resistant tot he passage of potassium ions and only slightly resistant to the passage of chlorine ions.

    - Also the Na+/K+ pump which uses active mechanisms in the membrane to continuously transfer 3Na+ ions out of the neurone and K+ ions in to keep the cell negatively charged. Anions cannot move, the K+ ions are balanced as there is concentration moving out so there is electrostatic attraction within, as there is a balance of Cl- ions with a smaller concentration in and electrostatic out. However Na+ is unbalanced as it is forced into the cell but stopped by membrane permeability.

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Brain Cells and Action Potentials

Brain Cells and Action Potentials

  • Action Potential:
    - If membrane allowed, Na+ would rush into the cell making it positive. If the cell depolarises slightly (becomes less negative) this happens and an action potential occurs. The threshold for this activation is about -50mV. Depolarisation is initially caused by the action of other neurones or sensory systems.

    Sequence of events:
    - Sodium channels open so the membrane potential increases to +40mV;
    - Then K+ channels open and Na+ channels close to efflux potassium ions.
    - The membrane potential then overshoots -70mV (known as hyperpolarisation) and the potassium channels close. Then diffusion brings the membrane back to the resting potential.

    - Channels are sensitive to membrane potential called voltage-dependent ion channels, there are over 70 types of ion channels discovered varying in the ions that they transmit and when or why they open and close.
    - Because the action potenial is fast (2/3 msec) the number of ions moving is very small. Short term, this means diffusion allows the membrane to move back to resting potential quickly, so cells can fire very often. Na+/K+ pump is only important in the long term.

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Brain Cells and Action Potentials

Brain Cells and Action Potentials

  • Action Potentials: - Some drugs affect the duration of depolarization including local anaethetics (e.g. Novocaine) which stop action potentials by blocking Na+ channels.

    - Depolarisation spreads down the axon and only goes one way as the Na+ channels remain closed briefly after the initial opening. Thus there is a wave of depolarization down the axon.

    - Action potentials are essentially the same, i.e. fire or dont fire, known as the All or None law. Thus the strength of the signal is from the rate of firing. Other information from timing or correlation of firing.
    - The refractory period is when the channels do not open. In the absolute period nothing can trigger the action potential. This sets the maximum firing rate and means signal is only in one direction down the axon. In the relative period there needs to be a higher depolarization to trigger the action potential, which means a stronger stimulus means more firing.
    - Sometimes neurones act to increase the potential of the cell i.e. hyperpolarise it. This makes it less likely to fire as more depolarization is needed to reach threshold value. This is an inhibitory system.

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Brain Cells and Action Potentials

Brain Cells andAction Potentials

  • Action Potentials:- Most neurons show some spontaneous activity, i.e. they fire even when not stimulated, so information can be carried by increases or decreases in firing rate.
    - Thicker neurones propagate action potentials faster. More importantly, myelination also increases the speed of propagation. There are no fluid or ion channels under the myelin so depolarisation moves within the neuron. This requires no energy and is faster as there is less membrane to depolarise.
    - Action potentials are regenerated at nodes of Ranvier, and this form of conduction is known as saltatory conduction.

    - Myelination makes complex brains fast, small and efficient enough to be useful. So if for nothing else, Glial cells are very important.
    - Unfortunately there is a price: Some diseases (i.e. MS) destroys myelin. In MS a persons own immune system attacks myelin in the CNS and thus disrupts normal neuronal signalling. Because damage occurs at a wide range of areas in the brain and spinal cord the symptoms are quite varied. Unfortunately there is no cure.

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Taste Preferences

Taste Preferences

Hunger and eating are good examples of the interactions of hardwired physiology with learning to produce adaptive behaviour, albeit with some important exceptions. There are 3 issues to consider in terms of eating, and the first is food selection which is how we know what or what not to eat.

  • Food Selection:
    - Rodents and humans are both omnivorous and live in a great variety of habitats, thus they have access to a wide range of potential foods and face a problem of choosing which foods to eat, as in nature they would not be labelled as 'food'. This can be contrasted to something like the koala that can only eat one food (a restricted range of gum leaves).

    - There are also many social influences on what is considered to be edible some of which depend on cultural factors, for example in India beef is not considered to be food as the cows are sacred in Hindi religions whereas in the UK beef is a common meat to be eaten. Some of these cultural influences have derived from environmental constraints, which is what foods grow well in a particular region that can bias social constraints on food choice, e.g. the prevalence of different staple grains in different regions.

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Taste Preferences

Taste Preferences

  • Food Selection:- There are also evolutionary influences from past diets in what we consider to be food: for example most adult humans cannot digest lactose because they do not have the critical enzyme lactase. However, people descended from cultures whose ancestors relied on dairy produce (especially those far from the equator where extra calcium was needed due to less sunlight) tend to show lactose tolerance.
    - This tolerance is genetically based and results in lactase being present throughout adulthood. As well as demonstrating genetic influences on food choice, the interaction between cultural factors and genetics is a great example of how evolution and behaviour interact.

  • Taste:- Tastes are supported by receptors on the tongue. Humans have 5 known tastes of sweet, sour, salty, bitter and umami, and rodents have an extra taste as well as these 5 of starch.
    - Odours are supported by receptors in the nasal cavity (the olfactory epithelium) which can be detected either orthonasally (sniffing) or reteronasally (via the mouth).
    - Flavours are a combination of taste and odour, and possibly texture. Most of what people mean when they say taste is actually flavour, which is why food tastes poor when you have a cold as you are losing the odour informaton.
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Taste Preferences

Taste Preferences

  • Preferences: - Animals show particular facial reactions when consuming tastes that they find palatable that contrast greatly with the facial reactions to tastes they find unpalatable. These reactions are conserved across species and provide one way of examining 'liking' in non verbal animals and human infants.
    - So to fully understand food preferences and aversions we must consider what animals choose to consume and how they consume it.
    - Some taste preferences are hardwired, such as sweet tastes which are preferred, whereas sour and bitter tastes are initially rejected. There is also only one hardwired craving which is for salt when they are deprived. So the vast majority of preferences and aversions that guide food choice must be learnt.
    - Learning is affected by how new foods are sampled: e.g. Neophobia is when there is a low consumption of novel foods; and Neophilia which is when animals show a tendency to sample small amounts of novel foods. These act together to support the exploration of new sources of food but to help protect from any ill effects that might occur.
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Taste Preferences

Taste Preferences

  • Acquired Dislikes:- Certain odours are found to be disgusting, e.g. faeces, but this is not innate as young children don't reject them, thus showing that there is evidence for socially acquired aversions.
    - The most commonly explored process is conditioned taste aversion (CTA) where flavours are paired with illness and are then rejected, even when the real source of the illness is known (e.g. chemotherapy patients reject foods paired with the treatment they get), therefore this process is not mediated by cognition. CTA works well over delay and is learnt in a single trial, plus it is especially good when learning with novel foods (enhancement of neophobia).

  • Aversion Studies:Garcia & Koelling (1966) - demonstrated that animals find it particularly easy to associate foods, as opposed to visual or auditory stimuli, with illness. Rats were given a saline solution which, when drunk, would set off an auditory or visual stimulus.
    - When the conditioned stimulus was paired with LiCl which induces nausea, the rats subsequently avoided the saline solution but not the water that was paired with the auditory/visual stimulus.
    - When the CS was paired with shock, rats subsequently avoided water paired with auditory/visual stimulus but not the salty taste.
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Taste Preferences

Taste Preferences

  • Taste Aversion Studies:Pelchat et al (1983)
    - Demonstrated that previously pleasant foods paired with nausea now taste "disgusting" while foods rejected for other reasons (e.g. they predict shock) do not change in taste quality. Similar dissociations are seen in humans, foods rejected due to allergies do not taste bad, while foods rejected due to pairing with illness do.

    - They paired sucrose with either LiCl or a shock until the sucrose was avoided in rats, then they examine the consumption and/or facial reactions to sucrose.

    - Shock and LiCl paired groups showed equivalently low levels of sucrose consumption. The LiCl group now reacted to sucrose with negative orofacial reactions, whereas the shock group still showed positive reactions (showing they still liked the taste but avoid drinking it).

    - Thus the dissociation between taste reactivity and consumption reinforced the idea that CTA is about rejecting foods paired with illness.
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Taste Preferences

Taste Preferences

  • Taste Aversion Studies:- Similar dissociations can be observed in humans. Rozin & Vollmecke (1986) contrasted two individuals who avoid peanuts. One of them has an allergy to peanuts and suffers rashes and/or difficulty breathing after eating them, so this person avoids peanuts as they are dangerous but likes the taste. The other person originally liked peanuts but got sick and vomited after eating them, so she now dislikes the taste while realizing they are not dangerous.
    - As with the rats, only nausea makes foods taste bad. However, most people report CTAs to only a very small number of foods so it cannot explain all learnt food choices.

    - Exposure to foods can be social (e.g. seeing family eat particular things) and in humans this seems to be mediated by cognitive or cultural factors. Rats also show a preference for foods eaten by other rats, but this is actually a very special form of learning where the CS is the odour of the food and the US is carbon disulphide (found in rats breath).
    - Conversely to CTA, preferences can be created by a recovery form illness known as the medicine effect. E.g. Rats on a protein deficient diet show preference for flavours paired with essential amino acids.

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Taste Preferences

Taste Preferences

  • Flavour Preference Learning:
    - Although the medicine effect is very interesting, like CTA is does not account for many of the food preferences observed in humans. More important are palatability and nutrient based preferences.
    Palatability-Based: Refers to the association of flavour (usually a neutral or disliked one) with a particularly palatable taste (e.g. learning to drink sweetened tea or coffee). This does not work if there is a delay between the two flavours and does not depend on nutrients being present. Similar learning processes can also produce dislikes if one flavour is unpalatable.

    Nutrient-Based: Refers to the association of flavour (usually a neutral or disliked one) with nutrients. This increases preference to the neutral flavour even in the absense of high deprivation levels. There is no need to taste the nutrients and it can work if there is a delay between tasting the cue flavour and the delivery of nutrients. But nutrient based learning is dependent on motivational state as some hunger is needed.

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Taste Preferences

Taste Preferences

  • Acquires Preferences:- Just like with CTA, preference learning can influence palatability as well as consumption; but flavour-flavour and flavour-nutrient learning is not the only sources of acquired preferences.
    - The medicine effect (increased preference for foods associated with recovery from illness.
    - Exposure: Preference increases with exposure which is classed as partially overcoming neophobia. Exposure can be social, as infants show preference for flavours in their mothers milk whilst rats show preference for foods eaten by other rats.

    - As an aside, the social learning of food preferences in rats is actually a conditioning phenomenon. The conditioning stimulus is the odour of the food and the unconditioning stimulus is carbon disulphide etc.
    - However this is a very special learning mechanism and does not show the same effects as seen with Pavlovian conditioning.

    - Innate factors provide the initial grounding for food choice but most is learnt.

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Motivation and Feeding

Motivation and Feeding

The basic nutrient sources from foods are: Carbohydrates (digested to glucose); Fats; and Proteins (digested to amino acids). From these we need to extract energy, also we need vitamins and amino acids for protein synthesis as well as minerals (e.g. sodium and potassium) for other processes. There are two stores of energy, the short term energy store of glycogen (especially found in the liver) and the long term energy store of triglycerides (stored in adipose tissue). But, this is not the form in which all food arrives and thus needs converting.

  • Metabolic Processes:
    - Glucose is the only fuel for neurones, and is used by other cells but requires insulin to do so. The liver is stimulated by insulin (a pancreatic hormone) to convert glucose into glycogen. The liver is also stimulated by glucagon (another pancreatic hormone) to reconvert glycogen to glucose. Insulin is released in anticipation of meals and when glucose is in the bloodstream.
    - Triglycerides are complex molecules consisting of glycerol and 3 fatty acids. When nutrients are being absorbed, fats, amino acids and glucose combine to form triglycerides. Adipose performs the conversion and stores them. They cannot be used directly as fuel but when the digestive system empties, adipose tissue reconverts triglycerides into glycerol and fatty acids. This is signalled by glucagon, sympathetic neural signals or catecholamine secretion.
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Motivation and Feeding

Motivation and Feeding

  • Meals:- Nutrients are needed relatively constant but, unlike cattle, we eat discrete meals. Thus we need start and stop signals.
    - Social/environmental factors are important as people are hungry at "mealtimes" and taught to eat what is on their plate. Seeing/hearing others eat promotes their own eating and breakfast food at lunch times is not as satisfying.
    - Cognitive factors are also important. Densely amnesic patients will eat several lunches if given the chance, although they would regulate their intake reasonably well.

  • Homeostasis:- Is an important concept in the regulation of feeding. This refers to a system where there is a variable to be regulated around a given set-point, a detector for the current level of the variable and a mechanism to correct any error.
    - A good example of a homeostatic system is a thermostat for the control of temperature. If the thermostat is at a given temperature, and the temperature rises above the set point, heaters are turned off and vice versa if below.
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Motivation and Feeding

Motivation and Feeding

  • Homeostasis:- Glucose is a possible variable to regulate. There are detectors both in the liver (sends signals to the brainstem via the vagus nerve) and the brain itself (the nucleus of the solitary tract) for blood glucose levels and changes in blood glucose do affect hunger, but you can disconnect the liver from the brain and shut down the NST and still get hungry.
    - Fat is another obvious possible target for homeostatic regulation and the liver is sensitive to the availability of fatty acids. Blocking fatty acid metabolism puts hunger up, but hunger and feeding survive lack of fat signals.
    -  So, homeostatic mechanisms centred on the regulation of either short term or long term energy stores in glucose or fat do play a role in starting and stopping meals, but they are not the only story as hunger and the regulation of feeding survive the removal of the detectors underpinning these mechanisms.
    - Furthermore, animals are not sensitive to glucose pre-loads immediately before meals and insulin increases prior to meals. Both of these facts indicate a role for anticipation and learning in the regulation of feeding which implies homeostasis must be an oversimplification.
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Motivation and Feeding

Motivation and Feeding

  • Oral and Taste Preferences:
    - Pleasure produced by a taste reduces with consumption, but change taste and consumption/liking recovers. Some diets work this way to bore you into eating less.
    - Nutrient-based preferences mean that tastes can predict nutrients and encourage eating. The volume through the mouth provides temporary signals to stop eating which are easily overridden, e.g. if nutrients are prevented from reaching the stomach (sham feeding) then feeding is almost continuous.
    - Thus, oral factors are not very important on their own but may play a role in eating beyond nutrient need.

    - A grumbling stomach is not actually a good signal for hunger as people without a stomach will still report hunger, nor is volume in a stomach a good satiety signal as if food in the stomach is replaced with saline, the animal eats to replace the food although an uncomfortably full stomach can stop feeding.
    - Oral and gastric nutrient detectors combine with the stomach volume cues to stop meals, e.g. prevent food escaping the stomach and still eat only a normal sized meal.
    - But blocking a signal from the stomach to the brain does not prevent regulation completely.

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Motivation and Feeding

Motivation and Feeding

  • Intestinal and Long-Term Factors:- Fats or proteins in the duodenum causes the secretion of cholecystokinin (CCK) which inhibits gastric emptying (regulating the contents of intestines) and is a potent satiety signal, albeit temporary (stops eating but does not prevent the start of a new meal once dissipated).
    - Oral, stomach and intestinal signals are anticipatory. Produce satiety in advance of nutrient uptake, but control meal size to prevent overeating.

    - Nutrient detectors in the liver act to continue satiety initally signalled elsewhere, while well fed adipose tissue secretes leptin which sensitises other satiety signals and increases metabolic rate.
    - Given the number of factors affecting eating you can expect many brain regions to be involved in some way:
    Lateral Hypothalamus (LH): - Lesions produce severe aphagia/adipsia which can result in death if not helped, but they can recover and regulate at a lower body weight. Stimulating LH leads to feeding suggesting that LH is the feeding centre, however this is too simplistic.

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Motivation and Feeding

Motivation and Feeding

Lateral Hypothalamus: - LH contains neurons which release melanin containing hormone (MCH) and orexin which both stimulate eating, and LH is also connected to brain systems of motivation and metabolism.
- LH is stimulated via the arcuate nucleus which releases a number of neurotransmitters that stimulate eating and reduce metabolism. This nucleus is sensitive to both leptin and insulin and can be inhibited by satiety signals.

Ventromedial Hypothalamus: - Lesions of this region result in obesity or overeating. Weight is gained initially but then can be regulated at a higher body weight as extra insulin is secreted to lower blood glucose etc.
- VMH is initially seen as the satiety centre and is located between the arcuate and paraventricular nuclei. The PVN is involved in lowering insulin release and other aspects of metabolism and receives input from the brain stem and arcuate nucleus.
- VMH lesions block this input, so satiety signals dont get to the PVN after lesions of the VMH but other satiety processes must exist as feeding is partially controlled.

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Motivation and Feeding

Motivation and Feeding

  • Obesity:- Obesity is a growing problem in the UK and elsewhere, only slightly behind tobacco as the largest preventable cause of death.
    - Body Mass Index (BMI) is a basic measure of whether someone is obese or not, with 20-25 being normal; 25-30 being overweight and 30+ being obese.
    - The basic problem is that the fuel going in is greater than the energy used. Simply eating less is not enough as the metabolic rate goes down when food is restricted so less energy is used.  Exercise can raise metabolic rate.
    - Both metabolic rate and fat percentage is partially genetic.
    - Many animal models of obesity and potential treatments are based on chemicals signalling satiety/hunger. Such simple disturbances do not contribute to much of the obesity seen in humans thus these models are unrealistc. But they may still provide possible treatments (e.g. leptin as a possible treatment to sensitize people to satiety signals.
    - Other treatments include serotonin and its agonists which suppress feeding, and Orlistat (Alli) which blocks the digestion of fats.
    - However most treatments include exercise or surgical reducion/bypass of parts of the gastric system.
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Genetic Effects on Behaviour

What we inherit (i.e. sperm and egg molecules, mitochondria 'mDNA' and genomic DNA) plus what we experience throughout life (i.e. the environment) results in how we behave. We now that genes influence our behaviour through family studies, twin studies, adoption studies and studying the effects of mutations.

Family studies: As relatedness decreases, so does the common genetic complement. An unrelated individual shares a small proportion of the original individuals genetic material.

Twin studies: Identical (monozygotic) twins share 100% of one anothers genetic material, whereas non-identical (dizygotic or fraternal) twins share, on average, 50% of one anothers genetic material which is the same as siblings. Twins are generally raised in identical environments.
- If a behavioural trait is genetically influenced, expect greater similarity between individuals with greater relatedness.

Adoption studies: Adopted children share their genetic material but not their environment with their biological parents. They also share their environment but not their genetic material with their adoptive parents. If a trait is genetically influenced, there should be a greater correlation between the trait in adoptive children and their biological parents and siblings than between the trait in children and their adoptive family.

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Genetic Effects on Behaviour

Adoption studies are thus powerful but difficult to undertake:
- Information on the adoptee and biological families may not be available;
- Ethical issues evolve re-approaching biological families about the child they gave away.
- Adoption process is not random, e.g. adopted children placed in non-representative families.
- Adopted children are not representative of the general population.
- Adopted children are subjected to the biological mothers in utero environment and early life influences.
- Adoption is rare in developed Western countries so there would be a small sample size.

  • Heston (1966):
    - Compared 47 adopted children whose biologial mothers had schizophrenia (Group 1) to adopted children whose mothers did not have schizophrenia (Group 2). 17% of group 1 developed this disorder whereas 0% of group 2 did.
  • Danish Adoption Study (1980):- Identified a large number of adults with and without schizophrenia who had been adopted shortly after birth. 13% of biological relatives of adoptees had SCZ-like disorders whereas only 1% of biological relatives of adoptees without SCZ had them.
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Genetic Effects on Behaviour

  • IVF:
    It is now possible to disentangle prenatal and inherited influences in humans:
    - In homologous IVF the parent related to the child is both, and the woman experiencing pregnancy is the biological mother.
    - In IVF with sperm donation the biological mother is the only relation to the child and experiences the pregnancy.
    - IVF with egg donation, the father is the only parent related to the child so the non biological mother experiences the pregnancy.
    - IVF with embryo donation means there is no parent related to the child and the non bio mother.

779 IVF-related pregnancies and resultant children were closely monitored in terms of maternal smoking, childs birthweight and the childs psychological profile.
- There was a positive association between variables in pregnancies where the mother is genetically unrelated to the offspring cannot be due to inherited factors from the mother.
- There is a positive association between variables in pregnancies where the mother is genetically related to offspring suggesting influence of heritable factors.
- Prenatal exposure to smoking in related/unrelated offspring resulted in lower birthweights. There is a significant association between maternal smoking and antisocial behaviour in related, but not unrelated group.

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Genetic Effects on Behaviour

How traits are inherited within families can give clues as to the number and type of genetic variants involved. Behavioural traits and psychiatric illness risk are typically underpinned by 'many variant of small effect' and 'few variants of larger effect'.

Family, twin and adoption studies allow a 'heritability' calculation. The proportion of variance in a trait which is attributable to genetic variation within a defined population in a specific environment. There is a 2x difference in correlation between MZ and DZ twins, i.e. Falconers formula: H squared = 2(r(MZ) - r(DZ)).
High heritability does not mean that the trait is unaffected by the environment. A trait may have perfect heritability in a population and still be subject to great changes resulting from environmental variation.

However, gap betwene heritability estimates and combined, known effects of individual genes: 'missing heritability'.
- Failure to identify all casual genetic variants, and underestimation of individual gene effects; neglect of sex chromosomes.
- Variability in environments, complex interactions between genetic variants and between genetic variants and the environment.
- The over estimation of heritability, transgenerational epigenetic effects.

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Genetic Effects on Behaviour

  • Effects of Mutations:
    - Inactivating (rare) mutations in some genes may substantially influence behaviour, e.g. MAOA.
    - Brunner syndrome results in impulsive aggression, arson, sexual violence, exhibitionism and mood and sleep problems.
    - There are two genetic variants at the start of the MAOA gene: a 3 repeat allele or 4 repeat allele. The latter have a higher association with risk taking behaviour.
    - There is some evidence for association between MAOA genotype and impulsivity in healthy individuals ad those diagnosed with ADHD. In males with MAOA-L there is higher physical aggression when exposed to it.

  • Finding Genes for Behavioural Phenotypes:
    - Complex behavioural and psychiatric phenotypes are influenced by many interacting genes and by the environment, e.g. MAOA mutations manifest differently.
    - Individual genes may affect many different bits of the brain and resultant behaviour. Genetic variant may predispose to particular behaviour patterns, but are not deterministic.
    Plomin Study (2010) - studied general cognitive ability in approx 8000 children. In the lowest and highest scoring 1000 individuals, they looked at 350000 genetic variants (changes in single DNA letters) across the genome and there was no variant significantly associated with 'g'.
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Physiological Functions of the Cerebral Cortex

  • Anatomical Features of the Human Cortex:
    - It is 2-3mm thick and formed from gyri and sulci. There are two types of cortex, primary (which is the end point of sensory pathways and thus receives sensory information) and association (involved in complex information processing and integration of information).
    - The neocortex has 6 layers containing different types of neurons and has approximately 10-14billion neurons. Pyramidal cells are the main cell type in layers III and V.
    - Korbinian Brodman (1908-9) divided the cortex into regions based on their cytoarchitecture. The main areas are the frontal (associated with personality), parietal (associated with tactile sensations and movement), occipital (associated with vision) and temporal (associated with memory) lobes of the brain.
    - Wilder Penfield (1891-1976) expanded brain surgery methods and techniques including mapping the various functions of the cortex to produce motor and somatosensory homunculi from the primary somatosensory and motor cortices. In the motor homunculus the hands, digits, and lips are represented as the largest areas on the cortex which means they are most highly innervated due to their complex functions, for example it requires a lot of innervation to the mouth to produce the facial expressions we make or to chew food. The somatosensory homunculus is shown similarly due to the amount of sensations we feel in the hands from touching objects and mouth from eating.
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Physiological Functions of the Cerebral Cortex

- The association cortex is the locus of integrated processing of multimodal information. Lesions of these areas can result in strange behaviours, for example Oliver Sacks wrote a book on a case of his where his patient mistook his wife for a hat due to suffering from visual agnosia, which is caused by damage to the visual association cortex. There are two types of this, apperceptive where a person is unable to recognize objects because they cannot perceive the correct forms of the object although their knowledge of it is intact; and associative where a person correctly perceives the forms and has knowledge of the objects but cannot identify them.

- Lesions to the frontal cortex can result in cognitive changes as this area is known as the 'central executive'. Phineas Gage was a case where an accident with a large metal rod pushed through his skull and damaging his frontal lobe. The doctor said: "The balance between his intellectual faculties and animal propensities seemed gone. He could not stick to plans, uttered the grossed profanity and showed little deference for his fellows. The railroad-construction company that employed him, which had thought him a model foreman, refused to take him back. So Gage went to work at a stable in New Hampshire, drove coaches in Chile and eventually joined relatives in San Francisco, where he died 11 years after his accident at the age of 36 after a series of seizures. Showing clear evidence of personality change.

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Physiological Functions of the Cerebral Cortex

  • Frontal Lobe:
    - The frontal lobe of the brain is subject to specific diseases such as frontal lobe dementia or Pick's disease, and frontal lobotomy used as therapy. This is where the thalamocortical fibres (i.e. corona radiata) are severed to disconnect emotional centres from the seat of intellect. It reduces problem behaviours such as aggression and blunted emotional reactivity, and is used to treat depression or schizophrenia. There are also cognitive tests of frontal lobe function such as the Stroop task (where you have to say the colour of the text of a word aloud, but the actual word will say a different colour), and the Wisconsin Sort task (sorting objects by shapes number and colours). Closed head injury disrupts this.

    - Frontal lobe functions: contains the motor and pre-motor cortices which are involved in primary and secondary levels of motor control, verbal fluency and design fluency. The prefrontal cortex is involved in motor control, adaptability of response patterns, programming/planning of sequences of behaviour, response inhibition, problem solving/executive functions, voluntary eye movements, perceptual judgements, attention and memory. Brocas area is involved in expressive speech, and the orbital cortex is involved in personality/social behaviour and emotions of the value of stimuli.

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Physiological Functions of the Cerebral Cortex

  • Temporal Lobe:
    Functions: - contains the primary and association auditory, and olfactory cortices; contains visual association areas along the ventral stream for the recognition of stimuli and colour vision; involved in memory, emotional and social behaviour; And it links past and present sensory and emotional experiences into a conscious self.
    - Capgras Syndrome is an issue with connecting recognition with emotion. e.g. prosopagnosia (a visual agnosia).

  • Parietal Lobe:- Benson's Syndrome is due to degeneration in the parietal cortex and is also known as posterior cortical atrophy.
    - A rare form of dementia, typically involved in stroke, associated with a host of cognitive disorders including asterognosia (inability to recognize items by touch) and spatial neglect. Middle cerebral artery is the most common cause of stroke.
    - Other deficits: to the post central gyrus = damage to proprioception, discrimination (tactile sensation); agraphism (inability to write).
    to the superior parietal lobule = Balint syndrome (cant reach for objects (optic ataxia).
    to inferior parietal lobule = conductive aphasia (speech repetition), Wernickes aphasia (difficulty comprehending); Alexia (inability to perceive written words); Asomatognosia (lack of awareness of body parts); Anosognosia (denies existence of illness).
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Physiological Functions of the Cerebral Cortex

  • Occipital Lobe:
    - Contains the primary visual cortex which outputs to the dorsal and ventral visual streams.
    - Damage to V1 causes blindsight

  • Language Processes:
    - The visual cortex receives written words as visual stimulation and sends this to the angular gyrus which transforms visual representations into an auditory code.
    - This sends information to Wernickes area which interprets the auditory code and projects information to Brocas area via the arcuate fasciculus which controls speech muscles via the motor cortex from which the word is pronounced.
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Neural Mechanisms of Learning and Memory

To survive, all organisms need to adapt to changes that occur in their environment. That is, they need to learn about events in their world. Learning is the storage of information as a function of experience that results in a relatively permenant change in behaviour. Memory is the stored information that is produced as a result of learning.

One of the most fundamental questions in neuroscience is how does the brain encode new information and how is it stored. One view of how the brain achieves this is by encoding information in networks of neurons. More specifically by modifying the strength of connections between neurons. It is the pattern of synaptic strength in a network that encodes information. In addition, it is generally thought that the retrieval of memory involves activation of the same pattern of synaptic connections.

If one accepts that neurons participate in the processes of learning, then it leads to the question of what types of events should we be looking for that cause neuronal changes and should we be looking in specific parts of the brain. There are several approaches to these questions, but we shall focus on looking at what happens in the brain at the cellular level during learning.

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Neural Mechanisms of Learning and Memory

  • Learning and the Synapse:
    - Of course, the human brain is a big place and methods that allow us to study changes in individual circuits, let alone individual neurons, during learning and memory in humans are not available. Therefore in order to address the issue, scientists have used animals. They face 3 questions: What model system to use? What types of brain circuits to look at? What type of learning to investigate?

    1) Model Systems - Scientists have often used what are called 'model systems'. The term moel systems here refers to the fact that animal preparations that display learning often have a much simpler or reduced central nervous system relative to humans. Certainly one of the most influential individuals in this area of research is Eric Kandel.

    2) Type of Brain Circuits - Even if we establish a particular model system it is important to establish what type of brain circuit should one be looking at. Different types of circuits could be used to support information processing. These range from simple mono-synaptic reflex arcs to superordinate circuits.
    - The earliest description of how such combination of circuits could support learning and memory stemmed from Donald Hebb (1949) where he postulated the existence of cell assemblies (groups of connected neurons) and that activity within this depended upon changes in synaptic strength.

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Neural Mechanisms of Learning and Memory

- The term synaptic strength refers to the fact that prior to learning a weak synaptic connection had little effect on the post-synaptic membrane potential. However, after the learning, synaptic strength is said to have increased when the same action potential crosses the same synapse but this time drives the post-synaptic membrane closer to the threshold for firing an action potential or indeed causes it to fire an action potential.

- The central role for the synapse in circuit formation was echoed in earlier work by Sherrington (1997) and Santiago Ramon y Cajal (1894).

- Hebb has been very influential and his postulate if often cited goes: "When an axon of cell A is near enough to excite a cell B repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A's efficiency, as one of the cells firing B, is increased." or, neurones that fire together wire together.

- Note, these changes are a result of changes that occur in the postsynaptic element of the synapse. This could be an increased surface area of the post synaptic membrane and more receptors.

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Neural Mechanisms of Learning and Memory

Type of Learning: Now that we have a theory regarding the types of circuit and the potential synaptic changes that may underlie learning we need to consider what type of learning we should look at. The answer to this is: the simpler the better.
- Habituation is the simplest form of learning in which an organism learns over repeated trials or presentations to ignore a weak or non-threatening stimulus that is neither rewarded nor punished. Habituation results in the decrease in the vigour or probability of a behavioural response that the stimulus normally elicits when it is novel. However, if the stimulus returns after a sufficiently long gap, then the behavioural response will return to near its initial strength.

- Sensitization is when an organism learns to increase the vigour of a response after a noxious or threatening stimulus. For example, an earth quake can sensitize one to weak environmental vibration. Sensitization can completely reverse habituation, a phenomena known as dishabituation.

  • Aplysia Californica:
    - Aplysia is a marine mollusc which can weigh up to 7kg with 20000 nerve cells arranged in 9 ganglia. The ganglia are very large cells and thus easy to record event related activity from.
    - Habituation in Aplysia is studied using the gill withdrawal reflex, a relatively simple sensory neuron to motor neuron pathway. This form of habituation can take the form of both short term and long term habituations.
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Neural Mechanisms of Learning and Memory

- Indeed all the characteristics of habituation shown in mammals are also shown by the Aplysia including dishabituation and sensitization.
- Habituation is accompanied not by a reduction in the action potential from the sensory neuron but by a reduction in the reaction of the motor neuron. This is not because the motor neuron has died or become fatigued as it still mediates the normal breathing response of the mollusc. This suggests that a change has occured at the synaptic junction between the sensory neuron terminal and motor neuron dendrites, that is, the synapse is no longer working as effectively. This is important because learning (habituation) in this situation is a result of a weakening of synaptic strength, which is contrary to Hebbs hypothesis.

What is the Mechanism? - Castelluci & Kandel (1974) used a technique called quantal analysis to show that the number of packets of neurotransmitter released by the pre synaptic component of the sensory neuron per action potential was decreased following habituation specifically to the sensory-motor pathway that was being habituated. This is therefore referred to as homosynaptic depression.
-
Then Klein et al (1980) showed that the decline in transmitter release was caused by a reduction in the influx of Calcium ions into the presynaptic terminal when an action potential arrived down the sensory neuron. This is the signal that drives synaptic vesicles towards the membrane during exocytosis.

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Neural Mechanisms of Learning and Memory

- This process of reduced release of neurotransmitter was found to underpin both short-term and long-term habituation. However, in the case of long term there were also changes in the physical characteristics in the pre synaptic element and the number of synapses between the sensory neuron and the motor neuron. So this evidence suggests that physical changes in the connectivity of neurons could contribute to the formation of long term memory.

  • Sensitization:
    - Using the same network of synaptic connections between the sensory neuron and the gill motor neuron, Castelluci & Kandel (1976) showed that a sensitizing stimulus (a shock to the animals tail) led to an increase in the amount of neurotransmitter released per action potential from the sensry neuron. This process was referred to as spike broadening, or heterosynaptic facilitation because it occurs at all synapses in the nervous system.
    - The shock activates a set of neurons called facilitator interneurons which uses serotonin (5HT). These facilitator interneurons deposit serotonin on receptors in the sensory neuron presynaptic terminal. Activation of these serotonin receptors causes the synthesis of cyclic adenosine monophosphate (cAMP) inside the sensory neuron pre synaptic terminal.
    - Increased cAMP activates protein kinase A to close potassium channels in the sensory neuron presynaptic membrane.
    - This delays the outflow of K+ ions during an action potential to temporarily slow the mechanism by which the membrane returns to its resting potential.
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Neural Mechanisms of Learning and Memory

- As a consequence of the slow return to baseline, the presynaptic terminal allows much more calcium ions to enter than normal. This in turn causes more synaptic vesicles to dock and release their neurotransmitter on to the motor neuron.
- As the motor neuron is now stimulated by more neurotransmitter it causes the cell to fire more frequently and this causes the gill muscle to contract more vigorously and for longer.

These findings show that learning and memory are accompanied by changes in the strength of connections between neurons. The results differ, however, from the mechanism originally proposed by Donald Hebb (1949). Hebb asserted that memory was a product of changes in the post-synaptic neuron. This is clearly not the case in Kandels experiments on Aplysia. All the changes underlying sensitization and habituation were mediated by pre-synaptic changes.
However, we cannot dismiss the possibility that a post synaptic process is involved in memory.

The above view is a very nice theory of how simple learning occurs in Aplysia. However, there have been critics of this theory. David Glanzman in particular has provided compelling evidence that Kandels theory is literally only one side of the story. Glanzman has highlighted that Kanzels theory has only focussed on changes that occur in the sensory neuron pre synaptic terminal. Kandel says virtually nothing about the role of changes in the postsynaptic side of the synapse during learning. According to Glanzman, the mechanism described by Kandel supports only the formation of short term habituation.

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Neural Mechanisms of Learning and Memory

- More specifically, the formation of long term habituation requires activation of post synaptic glutamate receptors (in particular NMDA). This leads to the removal of a specific subtype of glutamate receptor from the postsynaptic membrane known as AMPA receptors, which are responsible for normal fast synaptic transmission.

Glanzman has also tackled the issue of whether postsynaptic mechanisms contribute to sensitization. Glanzman suggests that the serotonin signal from facilitator interneurons reaches the postsynaptic motor neuron and causes an increase in the intracellular calcium ion levels in the motor neuron postsynaptic component.
- Glanzman suggests that this calcium ion signal causes more AMPA receptors to be inserted into the postsynaptic membrane. As a result, the postsynaptic membrane becomes more sensitive to glutamate released by the sensory neuron when it is stimulated. In addition, Glanzman suggests that Kandels presynaptic process supports only short term sensitization and that his postsynaptic mechanism supports long term sensitization.

Importantly, both Kandels and Glanzmans work highlight the critical and fundamental role played by synaptic connections between neurons in the acquisition of learning and the formation of long-term memories.

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Using Animal Models in Genetics

  • Defining Animal Models:
    - An animal model is a living, non-human being used to understand the biological basis of healthy and pathological human phenotypes, and how to alleviate the latter without the risk of harming an actual human being during the process.

    - Animal models are defined as being good or bad on 3 basis: 1) Face validity: i.e. does the model resemble the human phenotype; 2) Construct validity: i.e. do the model and human phenotype share common biological underpinnings; 3) Predictive validity, i.e. do therapeutic drugs have the same effect in humans and the model and can the model be used to screen for new treatments?

  • Types of Animal Model:
    Surgical - Occlusion of middle cerebral artery (causing stroke); Brain lesions; Gonadectomy.
    Administration of chemical or biological agents or radiation - Metazol administration for epilepsy; Immunisation with auto-antigens for autoimmune disorders; Administration of pathogenic and non pathogenic microorganisms for infectious diseases; Neurotransmitter agonists/antagonists or enzyme inhibitors; and Ionising radiation to cause tumours.
    Genetic - Manipulation of genomic DNA or administration of genetic material.
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Using Animal Models in Genetics

  • Advantages of Using Animal Models to Understand Gene Dysfunction:
    - Genomes are amendable to genetic manipulation and has a similarity to the human genome.
    - Experimental control (regulated background, environment).
    - Good breeders with short generation times.
    - Can be maintained in large colonies.
    - Examine in vivo effects of manipulation on brain function/behaviour (emergent property of integrated physiological systems); similarity of physiology to humans.
    - Wide repertoire of sophisticated behaviours.
    - Accessibility of neural tissue and amenability to procedures that would not be ethical in humans, e.g. interactions between drug administration and genetic lesions.

  • Disadvantages of Genetic Animal Models:- Genetic and physiological divergence from humans.
    - Different evolutionary histories (e.g. sensory modalities, social groupings).
    - Limited range of genetic modifications possible, possibility of species-specific effects.
    - Relevance to complex human behaviours influenced by combined effects of many genes.
    - Inability to accurately model human-specific phenotypes, e.g. language and psychosis.
    - Ethical issues regarding possible adverse effects, e.g. psychiatric phenotypes.
    - Models rarely have true face, construct and predictive validity.
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Using Animal Models in Genetics

  • Commonly Used Animal Models:
    - Caenorhabditis elegans (nematode worm) has a well specified neural circuit. Can mutate genome (e.g. RNA) to knockdown the expression of genes.
    - Drosophila melanogaster (fruit fly) traits that have been manipulated include eye colour and shape of wings but they are also interesting as they produce free radicals.
    - Danio rerio (zebrafish). Toxins are dissolved in water to test how their genomic mutations affect the survival of the fish.
    - Prairie (monogamous) and meadow (promiscuous) voles.
    - Mus musculus (and other mouse subspecies).
    - Rattus norvegicus (rat).
    - GM non human primates are very rarely used for research but do exist, e.g. the rhesus monkey ANDi which has a GFP transgene allowing him to fluoresce.

  • C.elegans:- Molecular and developmental characterisation by Brenner; first multicellular organism to have its genome sequenced. Well-defined development fate for every cell (1031 in adult male) and they are transparent.
    - It is the simplest organism with a nervous system (302 neurons), 'connectome' characterised.
    - There are many strains with defined genetic mutations and can be frozen and thawed.
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Using Animal Models in Genetics

- Can be exposed to double-stranded RNAi (infusion, injection or through bacterial ingestion) to disable individual genes.
- Can be administered by drugs readily.
- Exhibits chemotaxis, thermotaxis, learning and memory, mating behaviours.
- Can be used to study complex processes, e.g. nicotine dependence (acute response, tolerance, withdrawal and sensitization).

  • D. melanogaster:
    - Used as a genetic model from early 1900s onwards; genome sequenced and published in 2000
    - Only four pairs of chromosomes (3 autosome and one sex chromosome pair); Used to study fundamental mechanisms of transcription and translation.
    - Genome can be readily manipulated; Morphology is easily identifiable.
    - Used as a genetic model for neurodegenerative disorders (PD, AD, HD) and effects of oxidative stress/ageing.
    - Also used to examine genetics of circadian rhythm, sensory function, locomotor activity, courtship, pain and learning and memory.
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Using Animal Models in Genetics

  • Zebrafish:
    - Used as a lab model from 1960s onwards; Genome can be readily manipulated, e.g. transgenic expression of fluorescent proteins.
    - Expression/splicing of specific genes can be altered through use of 'morpholino antisense oligonucleotides' (which bind to complementary RNA sequences).
    - Embryos are large, robust, transparent and are able to develop on the outside of the mother.
    - Well-characterised, easily observable and testable range of behaviours: e.g. Diurnal sleep cycle, Anxiety-related and exploratory behaviours, Chemosensory behaviours, Response choice and inhibition, Social behaviours, Cognitive and executive functions.

  • Rodents:- Mice have been used as lab models since 16th century by inter alia, Harvey, Hooke, Priestley and Mendel; rats have been used from early 1800s.
    - Mouse (C57BL/6 strain) genome sequenced and published 2002; rat in 2004.
    - Mouse genome readily manipulated, rat genome less so until recently.
    - Mammals, therefore high degree of genetic and physiological homology with humans.
    - Range of sophisticated behavioural phenotypes, can examine genetic effects on: Courtship and mating behaviours, Dam-pup interactions, Social behaviours, Circadian rhythms, Motor function, Anxiety-related and exploratory behaviours, Cognition and executive function.
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Using Animal Models in Genetics

  • Genetic Rodent Models:
    - The rodent genome may be modified in a number of ways to assess effects on brain and behaviour:
    Selective breeding (inbreeding/outbreeding); Gene knockouts (or DNA element knockout); Transgenesis and 'knock in'; Mutagenesis using chemicals or radioactivity; Chromosomal mutations; Administration of molecules affecting gene expression/splicing.

  • Selective Breeding:Inbreeding - selected members of a founder strain are repeatedly inbred over many generations to ensure genetic homogeneity. Commonly used inbred strains include C57BL/6, BALB/c, 129 and BTBR (autism), and spontaneously hypertensive rat (ADHD); inbred strains can differ significantly in appearance and behaviour (polymorphisms).
    Outbreeding - Members of a founder strain are bred to unrelated individuals to ensure genetic heterogeneity.
    - Commonly used outbred strains include CD-1, MF1, Swiss-Webster (mice) and Lister Hooded, Long-Evans, Sprague Dawley and Wistar (rats).
    Recombinant Inbred Strains - Crosses between phenotypically distinct inbred strains for several generations can help identify regions of the genome affecting behaviour.
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Using Animal Models in Genetics

  • Gene Knockout:
    - Genetic insert can be designed so that 'knockout' only occurs at certain developmental stages or in certain tissues in response to exogeous chemical or after breeding with other GM mice (conditional knockout).
    - Knockout rats can now be generated using 'zinc finger nuclease' or CRISPR/Cas9 technologies. Systems that can be designed to selectively cut out parts of the genome,e.g. DNA or mRNA encoding ZFN of interest injected into 1 cell stage embryo.

  • Transgenesis and 'Knock-in':- Function is to insert exogenous sequence into the genome (e.g. animal gene into a plant)or to over-express endogenous genes. Two methods: Pronuclear injection of DNA sequence of interest which lacks specificity, re-target and copy number; or Modifying ES cells with DNA sequence homologous to target gene, inserted sequence may exhibit slightly altered function, e.g. single nucleotide mutation of interest.

  • Mutagenesis using chemicals: - Wildtype male mice treated with mutagen, e.g. N-ethyl-N-nitrosourea (ENU) so there are 1000 random point mutations in the genome. They are bred to wildtype female mice to produce G1 progeny. Eventually all phenotypically interesting descendants will theoretically possess just one point mutation which is associated with the phenotype of interest.
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Using Animal Models in Genetics

  • Chromosomal Mutations:
    - Occasionally, spontaneous chromosomal mutations may occur in rodents (e.g. due to impaired segregation of the chromosomes at meiosis); rates may be increased by mutagens, e.g. radioactivity.
    - Some of these animals may be fertile and can be bred.
    - Recently, a mouse model for Down syndrome (trisomy 21) was developed. In this Tc1 (transchromosomic 1) model, mice have a human chromosome 21 in addition to their own set of chromosomes. These mice exhibit phenotypes relevant to DS including altered: behaviour, synaptic plasticity, cerebellar morphology, heart development, mandible size.
    - The mouse model may now be used to investigate molecular pathways resulting in DS which has the potential for therapeutic approaches, e.g. 'inactivation' of additional chromosome.Overlap between DS & AD so there may be a common underlying mechanism.

  • Administration of Molecules Affecting Gene Expression:- 'Transient gene knockdown' to characterise function of poorly annotated genes. Short nucleic acids (DNA/RNA) e.g. antisense oligonucleotides, siRNA, morpholinos designed against specific gene introduced into brain means poor permeability/diffusivity.
    - Transgene inserted which makes e.g. siRNA and globally impairs gene activity 'knockdown organism'. Drug altering epigenome, e.g. sodium butyrate can be given and effects on brain/behaviour analysed to show effects on multiple genes.
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Using Animal Models in Genetics

  • New Genetic Approaches:
    Optogenetics - A light sensitive protein from algae. Take the gene for this protein and insert the DNA into specific neurons in the brain. Neurons communicate by firing action potentials. This is an electrical signal creased by opening and closing ion channels. So now you can cause neurons to fire just by flashing blue light.

    DREADDs - DNA encoding designer G-protein coupled receptors that do not respond to endogenous chemicals inserted into specific neurons/circuits.
    - Drugs binding to these receptors introduced into the animal to modulate (turn up, turn down) the activity of the circuit: assess resultant effects on behaviour.

  • Summary:- Animal model offer greater experimental control and amendability than human studies for examining genetic effects on behaviour. There are a number of commonly used genetic animal models, each with its own set of advantages and disadvantages.
    - Alterations to the genomic DNA sequence can lead to absence of gene expression ('knockout'), altered gene function ('knockin') or increased gene expression ('transgenesis'); these changes can be made to occur at selected timepoints. Brain gene expression can also be altered in a specfic manner by introducing chemicals that influence transcription.
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