Brain and neuropsychology

Structure of the Nervous system

The Nervous system: collects and responds to info in the environment. Controls working of different organs and cells including the brain.

Subdivisions: CNS + PNS. PNS = Peripheral nervous system. CNS = Brain and spinal cord. PNS = ANS + SNS. ANS = Automatic nervous system. SNS = Somatic nervous system. ANS = Sympathetic division and parasympathetic division.

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Functions of the Nervous system

CNS (Central nervous system) = The brain is divided into two halves (hemispheres). The right hemisphere controls the left side of the body and vice versa. The brain is the centre of conscious and where all decision making takes place. The brain stem governs some automatic functions and reflex responses.

PNS (Peripheral nervous system) = Receives messages from the CNS. Sends messages to CNS. Messages sent via neurons.

ANS (Autonomic nervous system) = Governs automatic functions. E.g. breathing, heart rate, digestion and the body's response to stress.

SNS (Somatic nervous system) = Sends info from the brain to the muscles, voluntary control of our muscles plus reflex responses. Takes in info from sensory organs, such as eyes and the skin.

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The automatic nervous system

Homeostasis: Keeping the body in a constant and balanced internal state. E.g. Levels of carbon dioxide in the blood controlled through regular breathing. Body temp maintained at 37 degrees centigrade by monitoring activity of the body's organs.

An 'Automatic' system: We don't have to consciously direct the ANS. Breathing, our heartbeat, etc, is vital to life so it needs to be involuntary.

Sympathetic nervous system: Works in opposition to the parasympathetic nervous system. A state of psychological arousal to prepare for the fight or flight response.

Parasympathetic nervous system: Produces the opposite effect on the sympathetic nervous system. This rest and digest response return the body to normal resting state once the threat has gone.

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The fight or flight response

The brain detects threat: The hypothalamus identifies a threatening event. Triggers the sympathetic division of the ANS to act.

The release of adrenaline: The ANS changes from resting state (parasympathetic) to an aroused (sympathetic) state. The stress hormone adrenaline is released from the adrenal glands into the bloodstream.

Fight or flight response: Immediate and automatic. Adrenaline targets the cardiovascular system, increasing heart rate and breathing. Also inhibits digestion and inhibits saliva production. Prepares the body to confront the threat (fight) or provide energy to run away (flight).

Once the threat has passed: Parasympathetic division returns the body to normal 'rest and digest' state. Digestion and hunger stimulated.

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James-Lange theory of emotion

Theory: Psychological arousal comes first and emotion after. Two similar theories were proposed and combined.

Physiological arousal first: An event causes physiological arousal in the following way: Hypothalamus arouses the sympathetic division of the ANS. Adrenaline is released and creates physiological arousal.

Emotion afterwards: Brain interprets the physiological activity. Causes emotion.

An example: Seeing a bear activates the sympathetic division. Muscle tense, heart pounds. These physiological changes interpreted as fear. The person runs away.

No physical changes = no emotion: If no physiological changes occur then emotions are not experienced. E.g. if you stand in front of your class and your heart rate doesn't increase, then you do not feel scared because there are no physiological changes.

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Evaluation for James-Lange

Evidence that emotions do come after arousal: Strength. The theory has real-life examples. A phobia of public situations can develop as a result of the anxiety. This shows that emotional responses are a response of physiological arousal such as increased heart rate.

Challenged by the Cannon-Bard theory: Weakness. We experience some emotions at the same time as physiological arousal and not one after the other. Therefore, the Cannon-Bard theory can explain emotional situations that the James-Lange cannot.

The James-Lange theory may be too simple: Weakness. The James-Lange theory is challenged by the two-factor theory. We need arousal plus social cues to correctly label the emotion we are feeling (Schachter and Singer). So the James-Lange theory does not explain how a person 'decides' the emotion they are experiencing.

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Neuron structure

Nerve cells send electrical and chemical signals. There are 100 billion of them in the human body. 

Types of neurons: Sensory - PNS to CNS. Long dendrites, short axons. Relay -  Sensory neurons to motor nuerons. Short dendrites, short axons. Motor - CNS to muscles and glands. Short dendrites, long axons.

Structure of neurons: Cell body - Nucleus with DNA. Axon - Carries signals from the cell body down the neuron, covered in myelin sheath. Myelin sheath - Fatty layer acts as insulation and gaps (Nodes of Ranvier) speed up signal. Terminal button - End of axon (part of synapse).

Electrical transmission: Resting state - Inside has a negative charge compared to outside. When it fires - Changes to a positive charge which causes an action potential.

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Synapses and chemical transmission

Neurons communicate using neurotransmitters, released from presynaptic to postsynaptic neuron across the synaptic cleft.

Neurotransmitters stored in vesicles at terminal buttons of the presynaptic neuron. Electrical signal releases neurotransmitters into the synaptic cleft.

Neurotransmitters attach themselves to the next neuron at postsynaptic receptor sites. The chemical message is turned back to an electrical impulse. Neurotransmitters in the synaptic cleft are broken down by enzymes and reabsorbed by presynaptic neuron.

Excitation and inhibition: Excitatory neurotransmitters increase the postsynaptic neuron's positive charge and make it more likely to fire. Inhibitory neurotransmitters increase the postsynaptic neuron's negative charge and make it less likely to fire.

Summation: Occurs if there are more excitatory signals than inhibitory signals. Makes neuron fire, causing an electrical impulse.

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Hebb's theory of learning and neuronal growth

Synaptic connections in the brain become stronger the more they are used. The brain has the ability to change and develop.

The brain changes structure and connections in response to new experiences (= learning). Any learning - at any age - will do this.

Learning leaves a trace (engram). This can be made permanent if we practice and rehearse what we are learning.

Cell assemblies are groups of neurons that fire together. The more they fire, the more the synaptic connections grow and strengthen. Neuronal growth occurs as the cell assemblies rewire to manage new learning.

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Evaluation for Hebb's theory

The theory is scientific: Strength. Hebb explained learning in terms of brain function which provided an objective basis for understanding behaviour. Shows that learning can be studied through brain processes.

Real-world application: Strength. Theory can be applied to education. He found that rats raised in stimulating settings were better able to find their way through mazes as adults. This could be applied to education by creating more stimulating environments to encourage learning.

Reductionist theory: Weakness. Hebb's theory reduces learning to a neuronal level. Means that other levels of understanding are ignored, such as Piaget's theory about how accommodation moves learning forwards. This is an issue because a more complete account of learning should discuss non-biological factors as well.

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Structure and function of the brain

The brain is divided into two hemispheres. The cerebral cortex covers the brain and is divided into four lobes. Frontal lobe = Front of the brain: thinking, planning. Motor area = at the back of the brain. Parietal lobe = Behind the frontal lobe, Somatosensory area at the front. Occipital lobe = Back of the brain, Visual area. Temporal lobe = Behind the frontal lobe and below the occipital lobe: memory. Auditory/language area (though Broca's area is in the frontal lobe).

Cerebellum: Receives information from the spinal cord and brain. The main role is movement, coordination and balance. Also involved in attention and language.

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Localisation of function

Localisation = Specific brain areas do particular jobs.

Motor area: Damage to the motor area in the left hemisphere affects the right side of the body and vice versa. 

Somatosensory area: The most sensitive body parts take up the most 'space' e.g. sensations for the face and hands use over half of the neurons available in the Somatosensory area. Damage here means less ability to feel pain and temperature.

Visual area: Right visual field of each eye sends information to the visual area in the left hemisphere, and vice versa.

Auditory area: Damage can lead to deafness.

Language area: Area in the left hemisphere only. Damage to Broca's area leads to difficulty remembering and forming words. Damage to Wernicke's area leads to difficulty understanding and producing language.

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Penfield's study of the interpretive cortex

Aim: Investigate patients' responses when their brains were electrically stimulated.

Method: Operated on people to treat their severe epilepsy. His technique meant that a conscious patient's brain was exposed and areas could be electrically stimulated. Patients could then report their thoughts and sensations.

Results: With temporal lobe stimulation, patients recalled experiences or recalled feelings associated with the experiences, including experiences of deja vu. The same memory was recalled each time the same area was stimulated.

Conclusion: Suggests that memories of previous experiences are stored in the temporal lobe. An associated area stores the personal meaning of the experience.

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Evaluation for Penfield

Precise method: Strength. Penfield used a very precise method of studying the brain. He could stimulate the exact same area of the brain repeatedly and patients could report their experiences. This enabled him to produce an accurate 'map' of brain function.

Unusual sample: Weakness: Ppts in the study made up an unusual sample. The patients were suffering from severe epilepsy. Could mean that any findings produced were not reflective of people with non-epileptic brains.

Mixed results in later research: Weakness. Penfield's later research did not always support his original findings. In fact only 40 out of 520 patients he studied reported vivid memories when their temporal lobe was stimulated. Suggests that the interpretive cortex does not always respond the same way.

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Cognitive neuroscience

Scientific study of the influence of brain structures on mental processes. Aims to create a detailed map of localised functions in the brain.

Structure and function of the brain relate to behaviour: Frontal lobe includes the motor area which controls and coordinates movement. Temporal lobe includes the amygdala which processes emotion and has been linked to aggression. 

Structure and function of the brain relate to cognition: 'Cognition' refers to the mental processes of the mind - the memory and perception. Different types of long-term memories are located in different areas of the brain.

Cognitive neuroscience and mental illness: Low serotonin affects thinking (e.g. suicidal thoughts) and behaviour (low mood, depression).

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Neurological damage

The importance of localisation: The effect of any damage depends on the area of the brain affected because functions are localised.

The effects of strokes: When the brain is deprived of oxygen because of disruption to its blood supply, the specific areas affected will die. The effects may not be permanent if other parts of the brain take over localised functions.

Effects of neurological damage on motor ability: Damage to the motor area can lead to the person struggling with fine and complex movements. Damage to the left hemisphere affects the right side of the body and vice versa.

Effects of neurological damage on behaviour: Brain damage can lead to 'aphasia' - an inability to understand and use language. Broca's aphasia leads to problems producing speech. Wernicke's aphasia affects the understanding of speech.

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CT scans

Large doughnut-shaped scanner rotates around the person to take lots of X-rays of the brain. Images are taken from different angles and are combined to build up a detailed picture.

Strengths:

  • Useful for revealing abnormal structures such as tumours.
  • Quality of the images provided is higher than traditional X-rays.

Weaknesses:

  • Requires more radiation than X-rays.
  • Only produces still images.
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PET scans

Patient is injected with a radiative substance such as glucose. Brain activity is shown on a computer screen.

Strengths:

  • Shows the brain in action.
  • Shows localisation of function when a person asked to perform a specific task.

Weaknesses:

  • Expensive
  • Images difficult to interpret
  • Ethical issues due to the injection of radioactive substances
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fMRi scan

Measures changes in blood oxygen levels in the brain. Brain activity displayed as 3D images produced on a computer screen.

Strength:

  • Shows the brain in action
  • Clear images
  • No radiation

Weaknesses:

  • Expensive
  • A person may stay very still
  • A time lag between activity and image appearing
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Tulving's 'gold' memory study

Aim: Investigate whether thinking about episodic memories produces different blood flow patterns from those produced when thinking about semantic memories.

Method: 6 ppts were injected with radioactive gold. Repeated measures design, each ppt did:

  • Four episodic trials - thought of personal experiences.
  • Four semantic trial - thoughts of facts

Blood flow in the brain was monitored on a PET scan

Results: Different blood flow patterns found in three out of six ppts. Semantic memories created a concentration of blood flow in the posterior cortex. Episodic memories created greater flow in the anterior cortex.

Conclusion: Episodic and semantic memories are localised in different parts of the brain. Memory has a biological basis.

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Evaluation for Tulving

Objective evidence: Strength. The study produced scientific evidence. Used evidence from brain scans that is difficult to fake, unlike other psychological investigations where you can be less sure that ppts are behaving genuinely. This means that Tulving produced unbiased evidence.

Problems with the sample: Weakness. The sample was restricted. Only 6 ppts were used and differences in blood flow for episodic and semantic memories were seen in only 3 ppts. This means that the results were inconclusive.

Are there different types of memory?: Weakness. Episodic and semantic memories are often very similar. Memories for personal events also contain facts and knowledge about the world so it is difficult to work out which type of memory is being studied. This may explain why the evidence from Tulving's study was inconclusive.

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