Biopsychology

Men and women respond differently to stressful situations. Taylor et al (2000) suggest that women show more ‘tend and befriend’ behaviours, which involves them protecting themselves and their young through nurturing behaviours and forming protective alliances with other women. Women may have a difference response because they are often the primary caregiver and fleeing would put their offspring at risk. Studies suggest that there may be a physiological response to stress that inhibits flight – the release of hormone oxytocin, which increases relaxation, reduces fearfulness and decreases the stress responses characteristic of the fight-or-flight response.

Negative consequences. The stressors of modern-day life rarely require the physical activity that fight-or-flight prepares the body for. When the stress response is repeatedly activated, this can have an impact on humans' wellbeing e.g. increased blood pressure can lead to physical damage of the blood vessels and eventually lead to heart disease. In addition, although cortisol may assist the body in fighting a viral infection or healing damaged tissue, too much cortisol suppresses the immune response, shutting down the process that fights infections.

Alternative Response. Gray (1998) argues that the first reaction to a threat is not to fight or flee but to avoid confrontation. Argues that most animals typically, at first, show the ‘freeze response’ – a ‘stop, look and listen’ response where the animal is hypervigilant. The adaptive advantages of this response for humans are that ‘freezing’ focuses attention and makes them look for new information in order to make the best response for that particular threat.

Positive behaviours in response to stress. Von Dawans et al (2012) – challenges idea that men only respond with fight-or-flight under stress whilst women are more prone to ‘tend and befriend’. Von Dawans et al found that acute stress can actually lead to greater cooperative and friendly behaviour, explaining situations like the 9/11 terrorist attack. One reason for this may be that human beings are fundamentally social animals and it is the protective nature of human social relationships that has allowed our species to survive.

Genetic basis for gender differences. Lee and Harley (2012) – the SRY gene found exclusively on male chromosome directs male development, promoting aggression and resulting in the fight-or-flight response. SRY gene may prime males to respond to stress in this way by the release of stress hormones such as adrenaline and increased blood flow to organs involved in the fight-or-flight response. The lack of the SRY gene combined with the action of oestrogen and oxytocin may prevent this response to stress in females.

One limitation of localisation is that not all psychologists agree with the view that cognitive functions are localised in the brain. Lashley (1930) introduced equipotentially theory, which believes that basic motor and sensory functions are localised, but higher mental functions are not. Lashley argued that intact areas of the cortex could take over responsibility for specific cognitive functions following injuries to the area normally responsible for that function. According to this explanation, the effects of damage would be determined by the extent rather than location of the damage. Further support for this theory has come from cases of humans regaining some of their cognitive abilities following damage to specific areas of the brain, further suggesting that functions are not limited to one specific area of the brain. Therefore one limitation of the localisation theory is there is evidence to suggest that some functions can be carried out by different areas of the brain.

A strength for the two language centres is that there is research support from aphasia patients. Excessive aphasia (also known as Broca’s aphasia) is an impaired ability to produce language and in most cases is caused by brain damage in Broca’s area. Receptive aphasia (also known as Wernicke’s aphasia) is an impaired ability to understand language, an inability to extract meaning from spoken or written word and is usually the result of damage in Wernicke’s area. This therefore shows the importance of Broca’s area in the production of language and Wernicke’s area in the comprehension of language. Therefore one strength of the localisation of function is that it is supported by aphasia patients.

A limitation of localisation of function is that there are individual differences. Research from Bavelier et al (1997) found in a study of silent reading a variety of areas of the brain were activated across participants, including the right temporal lobe and the left frontal, temporal and occipital lobes. In addition, Harsty et al (1997) found that women have proportionally larger Broca’s areas and Wernicke’s areas than men. This is a problem for localisation of function as it suggests that where functions are located in the brain is not the same for everyone and can depend on the individual. Therefore one limitation of localisation of function is that individual differences mean it is not possible to generalise the same assumptions to everyone.

One limitation of localisation of function is that it has been argued that how brain areas communicate with each other is more important than which brain region is responsible for which process. Wernicke claimed that although different regions of the brain have different functions, they are interdependent in the sense that in order to work they must interact with each other. For example in 1892, Dejerine described a case in which the loss of an ability to read resulted from damage to the connection between the visual cortex and Wernicke’s area. This suggests that complex behaviours such as language, reading and movement are built up gradually as a stimulus enters the rain, then moves through different structures before a response is produced. Therefore damage t the connection between any points in this process can result in impairments that resemble damage to the localised brain region associated with a specific function. Therefore it is arguably more important to focus on how the areas of the brain communicate with each other as well as where functions are located.

One limitation of Broca’s area is that language production may not be limited to that area alone. Dronkers et al. (2007) re-examined the preserved brains of two of Broca’s patients using MRI imaging and found that other areas besides Broca’s area could also have contributed to the patients’ reduced speech abilities. This is significant because although lesions to Broca’s area alone can cause temporary speech disruption, they do not usually result in severe disruption of spoken language, suggesting that language and cognition are far more complicated and involve networks of brain regions rather than being localised to specific areas. Therefore a limitation of Broca’s area is that it alone does not appear to be responsible for language production.

It is assumed that the main advantage of brain lateralisation is that it increases neural processing capacity (the ability to perform multiple tasks simultaneously). Rogers et al. (2004) found that in a domestic chicken, brain lateralisation is associated with an enhanced ability to perform two tasks simultaneously (finding food and being vigilant for predators). Using only one hemisphere to engage in a task leaves the other hemisphere free to engage in other functions. This provides evidence for the advantages of brain lateralisation and demonstrates how it can enhance brain efficiency in cognitive tasks. However a limitation of this research is that it uses animals instead of humans, and fundamental differences between the two mean that this research has limited applicability. Therefore whilst a strength of lateralisation is that there is evidence that it enhances brain efficiency, it is important to consider the limitations of such research.

It has been suggested that there is a relationship between hemispheric lateralisation and immune system functioning. For example those that are left-handed tend to have more superior right-hemispheric skills but are more likely to suffer higher rates of allergies and problems with the immune system. Tonnessen et al (1983) found a significant relationship between handedness and immune disorders whilst Morfit and Weekes (2001) found that left handers had a higher incidence of immune disorders in their immediate families than did right handers. This therefore suggests that the same genetic processes that lead to lateralisation may also affect the development of the immune system.

Lateralisation of function seems to change throughout an individual’s lifetime with normal ageing. Across many types of tasks and many brain areas, lateralised patterns found in younger individuals tend to switch to bilateral patterns in healthy older adults. Szaflarski et al. (2006) found that language became more lateralized to the left hemisphere with increasing age in children and adolescents, but after the age of 25, lateralisation decreased with each decade of life. It has been suggested that this may be to compensate for age-related declines in function in some way. Therefore a limitation of lateralisation is that it does not apply equally to all age groups.

Gazzaniga (1998) argue that some of the early discoveries from split-brain research have been disconfirmed by more recent discoveries. For example, split-brain research had suggested that damage to the left hemisphere was far more detrimental to language function than was damage to the right. However, case studies have shown that this is not always the case. For example, Turk et al., (2002) found that a patient known as J.W. developed the capacity to speak out of the right hemisphere about information presented to the left or to the right brain. Therefore one limitation of split-brain research is that it may not be correct to assume that language is limited to the left hemisphere.

The split-brain procedure is rarely carried out nowadays, meaning there is a limited number of individuals that can be used for research. Andrews (2001) argues that many studies are presented with as few as three participants, or sometimes just the one. Conclusions have therefore been drawn about the function of the brain from individuals who either have a confounding physical disorder (making the procedure necessary) or have had a less complete sectioning of the two hemispheres than was originally believed. Therefore a limitation of split-brain research is that it has limited generalisability to the wider population, limiting its usefulness.

One strength for plasticity of the brain is that there is research support from animal studies. Kempermann et al (1998) investigated whether an enriched environment could alter the number of neurons in the brain of rats and found that those housed in complex environments had an increased number of neurons in the hippocampus in comparison to those housed in laboratory cages. This supports plasticity of the brain as it shows how environmental factors can lead to changes in the development of neural pathways. Therefore one strength of plasticity is that research support is provided, although it is important to recognise the limitations of animal studies.

A strength of plasticity is that it is also supported by research into plasticity in humans. Maguire et al (2000) found that London taxi drivers have a much larger posterior hippocampus compared to a control group and the size was positively correlated with the amount of time spent as a taxi driver. This supports plasticity as it shows that complex memory training (taxi drivers must memorise huge areas) can cause changes in certain areas of the brain. Therefore plasticity is also supported by research into plasticity in humans, increasing its validity as a theory.

Functional recovery after trauma is supported by research from animals. Tajiri et al (2013) gave transplants of stem cells into regions of the brain affected by traumatic injury, and found that in the brains of the rats in the stem cell group there was clear development of neuron-like cells in the area of injury, alongside a solid stream of stem cells migrating to the brain’s site of injury. This therefore indicates the role of stem cells in regaining brain functioning. Therefore one strength of functional trauma is that there is research to support, although it is important to consider the limitations of animal research.

A limitation to functional recovery that the ability of the brain to recover from trauma varies with age. Studies have suggested that abilities thought to be fixed in childhood can still be modified in adults with intense training. Despite these indications of adult plasticity, Elbert et al (2001) conclude that the capacity for neural reorganisation is much greater in children than in adults, as demonstrated by the extended practice that adults require in order to produce changes. Therefore a limitation to functional recovery is that the older the individual is when trauma occurs, the more challenging it is to make and maintain changes.

A strength of functional recovery is that research support has shown educational attainment can have an effect on recovery after a traumatic brain injury. Schneider et al (2014) found that patients with the equivalent of a college education are seven times more likely to be disability-free a year after a moderate to traumatic brain injury compared to those who didn’t finish high school. This is important as this suggests that those engaging in further education were in an environment that encouraged the development of neural pathways, aiding in their ability to recover from a brain injury. Therefore a strength of functional recovery is that data from humans supports it.

fMRI

Strengths: Non-invasive and does not expose the brain to potentially harmful radiation (as PET does) Offers objective and reliable measure of psychological processes - which verbal reports cannot do.

Limitations: Not a direct measure of neural activity as it measures blood flow - not truly quantitative measure of mental activity in those areas. Argued it overlooks the networked nature of brain activity as it focuses only on localised activity in the brain - communication is argued to be critical to brain function, which fMRI does not measure.

Post-Mortem

Strengths: Allows for more detailed examination which is not possible through scanning techniques e.g. hypothalamus + hippocampus. Harrison (2000) - play a central part in understanding of origins of schizophrenia e.g. structural abnormalities + neurotransmitter systems.

Limitations: Time and matter of death can impact the brain, as well as the length of time between brain and post-mortem. Retrospective as can only be done following the person’s death.

EEG

Strengths: Provides a recording in real time - can accurately measure a particular task or activity and the brain activity associated with it. Useful in clinical diagnoses e.g. epilepsy as normal EEG readings suddenly change due to disturbed brain activity.

Limitations: Cannot reveal deeper regions without implanting electrodes, which can only b done in non-humans due to the ethical implications. Can pick up activity on several neighbouring electrodes, making it hard to identify the exact source.

ERP

Strengths: Continuous measure of processing in response to stimulus - can determine how processing is affected by specific experimental manipulation. ERP can measure the processing of stimuli even in absence of a behavioural response. ERP readings make it possible to monitor ‘covertly’ without needing a person to respond to them.

Limitations: Requires a large number of trials to gain meaningful data. Only sufficiently strong voltage changes generated across the scalp are recordable. Important electrical activities occurring deep in the brain are not recorded, meaning that the generation of ERPs tends to be restricted to the neocortex.

Hughes (1977) studied the circadian hormone release in 4 participants stationed at the Antarctic Station. In February (the end of the Antarctic summer), cortisol levels followed the familiar pattern, reaching their highest point as the participants awoke, and their lowest point as the participants retired to bed. However after three months of continuous darkness, this patterned had changed, with the peak levels of cortisol now being at noon, rather than as the men awoke. This suggests the importance of light in the regulation of hormone cycles. However other research using scientific communities in the Arctic found no such disruption of cortisol release patterns.

Early research studies of circadian rhythms suffered from an important flaw when estimating the ‘free-running’ cycle of the human circadian rhythm. In most studies, participants are isolated from variables that might affect their circadian rhythms, such as clocks, radios and daylight. HOWEVER they were not isolated from artificial light because it was generally though that dim artificial light would not affect their circadian rhythms, which research has shown is not true. For example, Czeisler et al. (1999) altered participants’ circadian rhythms down to 22 hours and up to 28 hours by using dim artificial lighting alone.

Chronotherapeutics is the study of how timing affects drug treatment. It is essential that the right concentration of a drug is released in the target area of the body at the time it is most needed. For example, the risk of heart attack is highest during the early morning hours after awakening. Therefore chronotherapeutic medications have been developed with a novel drug delivery system. These medications can be administered before the person goes to sleep at 10pm, but the actual drug is not released until the vulnerable period of 6am to noon (Evans and Marain, 1996).

The SCN responds to light entering the eye, meaning it is sensitive to cycles of day and night. Buhr et al. (2010) argue that temperature rather than light controls our body clock. Light may be the trigger, but the SCN transforms information about light levels into neural messages that set the body’s temperature. Body temperature fluctuates on a 24-hour circadian rhythm and even small changes in body temperature can send a powerful signal to our body clocks - Buhr et al. found that these fluctuations in temperature set the timing of cells in the body, and therefore cause tissues and organs to become active or inactive.

A study by Tucker et al (2007) suggests that differences in sleep patterns are largely biologically determined and may even be genetic in origin. Participants were studied over 11 consecutive days and nights in a highly controlled lab environment. The researchers assessed sleep duration, time to fall asleep and the amount of time in each sleep stage and found large differences in each of these characteristics, which showed up consistently across the eight nights. Doe deep sleep (stages 3 and 4), the individual differences were particularly significant, showing that differences between participants were not driven by circumstance, but were at least partially biologically determined.

There is some support for the importance of BRAC from studies of elite performers. Ericsson et al. (2006) studied a group of elite violinists and found that, among this group, practice sessions were usually limited to a duration of no more than 90 minutes at a time, with practice systematically distributed during the day in these 90-minute segments. Ericsson’s analysis also indicated that the violinists frequently napped to recover from practice, with the best violinists napping more than their teachers. Ericsson discovered the same pattern among other musicians, athletes, chess players and writers.

Menstrual cycle can also be controlled by exogenous cues. When several women of childbearing age live together and do not take oral contraceptives, their menstrual cycles tend to synchronise. In one study, daily samples of sweat were collected from one group of women and rubbed onto the upper lips of women in a second group.  The groups were kept separate yet their menstrual cycles became synchronised with their ‘odour donor’ (Russell et al., 1980). This suggests that the synchronisation of menstrual cycles can be affected by pheromones. Pheromones act in a similar way to hormones, but have an effect on the bodies of people close by rather than the body of the person producing them.

Penton-Voak et al. (1999) suggests that human mate choice varies across the menstrual cycle. Women generally expressed a preference for ‘slight feminised’ faces when picking a partner for a long-term relationship. However, when in the ovulatory phase of their menstrual cycle, women showed a preference for more masculinised faces. This preference is believed to represent a preference for kindness and cooperation in parental care in long-term mates, but a preference for males with ‘good genes’ for short-term liaisons so that these genes might be passed on to their offspring.

Belief in an infradian rhythm based on phases of the moon remains strong. For example, many midwives believe that more babies are born during a full moon than during in a new moon, but the statistics show that this is a purely subjective association (Arliss et al., 2005). Likewise, surveys of workers in the mental health professions have shown a persistent belief that the full moon can alter behaviour (Vance, 1995), despite studies failing to find any consistent association. Occasional studies have found correlations between the phase of the moon and various aspects of human behaviour, but there is no evidence of a causal relationship (Foster and Roenneberg, 2008).

The importance of the SCN as an endogenous pacemaker has been demonstrated in animal studies. Morgan (1995) bred a strain of hamsters so they had abnormal circadian rhythms of 20 hours. SCN neurons from these abnormal hamsters were then transplanted into the brains of normal hamsters. These normal hamsters then displayed the same abnormal circadian rhythm of 20 hours, showing that the transplanted SCN had imposed its pattern onto the recipients brains. Further confirmation of the importance of the SCN came in the reverse experiment, planting SCN neurons from normal hamsters into the brains of abnormal hamsters.

Under normal conditions the ‘master clock’ (the SCN) coordinates all bodily rhythms. However, in some circumstances can become out of step with each other. Folkard (1996) studied a university student, Kate Aldcroft, who volunteered to spend 25 days in the controlled environment of a laboratory. During her time in the laboratory she had no access to daylight or other zeitgebers that might have rest the SCN. At the end of the 25 days her core temperature rhythm was still at 24 hours. However, her sleep-wake cycle had extended to 30 hours, with periods of sleep as long as 16 hours being recorded.

Support for the role of melanopsin in setting the circadian rhythm comings from blind people. Some blind people are still able to reliably retrain their circadian rhythms in response to light, despite a total lack of image-forming visual perception (e.g. lack of rods and cones). Skene and Arendt (2007) estimate that the vast majority of blind subjects who still have some light perception have normally entrained circadian rhythms. This suggests that the pathway from retinal cells containing melanopsin to the SCN is still intact. As further evidence for the importance of this pathway in setting the biological clock, people without light perception show abnormal circadian entrainment.

Burgess et al. (2003) found that exposure to bright light prior to an east-west flight decreased the time needed to readjust to local time on arrival. Volunteers participated in one of three treatments (continuous bright light, intermittent bright light, dim light), each of which shifted their sleep-wake cycle back by one hour a day over three days. Participants exposed to continuous bright light shifted by 2.1 hours, intermittent by 1.5 hours and dim light 0.6 hours. As a result, participants in the first treatment group felt sleepier 2 hours earlier and woke 2 hours earlier (closer to the local time conditions they would find after their flight).

Vetter et al (2011) investigated the importance of light in the regulation of the sleep-wake and activity-rest patterns of two groups of volunteer participants over a five-week study period. One group remained in normal ‘warm’ artificial lighting, whilst the other was in an artificial ‘blue-enriched’ light. All participants kept a daily sleep lo and wore devices to measure their movement. Participants working in the warm light synchronised their circadian rhythms with natural light each day, but the blue light group did not show the adjustment and synchronised their rhythms to office hours, showing that the dominant zeitgeber for the SCN is light.