Psychology- Biopsych part 2 the brain, biological rhythmss

What does localisation of function mean?

The theory that different areas of the brain are responsible for different behaviours, processes or activities.

Where is the motor cortex found and what is its function?

Found in both hemispheres in the frontal lobe. Controls voluntary movement in the opposite side of the body.

Where is the somatosensory cortex found and what is its function?

Found in both hemispheres in the parietal lobe. Responsible for sensory information, production of sensations.

Where is the auditory cortex found and what is its function?

Found near the ears in both hemispheres in the temporal lobe. Responsible for analysing hearing and speech based information.

Where is the visual cortex found and what is its function?

Found in the occipital lobe in the back of the brain in both hemispheres. Responsible for processing and interpreting visual information.

Where is Broca’s area found, what is it responsible for and what are the effects of its damage?

Found in the left frontal lobe and responsible for speech production. Damage to Broca’s area causes Broca’s aphasia characterised by effortful speech made up of short sentences with a very simple grammatical structure. These patients understand language and so know what they want to say but have difficulty articulating it.

Where is Wernicke’s area found, what is it responsible for and what are the effects of its damage?

Found in the left temporal lobe and responsible for language comprehension. Damage to Wernicke’s area causes Wernicke’s aphasia whereby the patient speaks with normal grammar and rate but they leave out verb and tenses and so their speech does not make sense. Sentence length and intonation is normal but without meaning and they may talk excessively.

Brain scan evidence of localisation.

Peterson et al 1988 used brain scans to demonstrate how wernickes area is active during a listening task and Broca’s area during a reading task suggesting these areas of the brain have different functions.

Tulving et al 1994 in a study of LTM found that semantic and episodic memories reside in different parts of the prefrontal cortex.

This produces scientific evidence of localisation of function as the methods are objective and empirical.

Neurosurgical evidence of localisation.

Neurosurgery may sometimes be used for extreme cases of OCD and depression e.g. Dougherty et al 2002- 44 OCD patients underwent a cingulotomy and after 32 weeks a third had successfully responded to surgery.

This suggests that symptoms and behaviours associated with serious mental disorders are localised.

Case study evidence of localisation.

E.g. case study of Phineas Gage who had a drastic accident in which a piece of iron went through his skull and damaged a part of his frontal lobe. As a result of this accident, Gage experienced a change in personalty e.g. anger. This change provided evidence to support the theory of localisation as it was believed the area that was damaged was responsible for personality.

However, case studies can lack generalisability to other people, because a case study deals with only one person or small group e.g. Phineas Gage who experienced something very unusual. Therefore, we can never sure whether the conclusions drawn from this case applies elsewhere. Therefore, the results of the Phineas Gage case study are not generalisable because we can never know whether the case investigated is representative.

What is a weakness of localisation of function?

The notion of plasticity goes against the theory of localisation. if the brain becomes damaged e.g. during an accident which causes a person to lose a particular function, the rest of the brain appears to attempt to mend itself to recover lost neurological functioning e.g. cases of stroke victims recovering lost language abilities after a stroke - functional recovery. This is a problem for the localisation of function argument as plasticity like this supports the holistic theory of the brain

What is plasticity?

The brains tendency to change and adapt as a result of experience and new learning.

What is synaptic pruning?

During infancy the brain experiences a rapid growth in the number of synaptic connection- 15,000 by ages 2-3, nearly twice as many as there are in the adult brain. As we age, rarely used connections are deleted and frequently used connections are strengthened. 

Research into plasticity: Eleanor Maguire et al 2000.

Studied the brains of London taxi drivers using an MRI scanner. Found an increase in the volume of grey matter in the posterior hippocampus compared to a control group. This part of the brain is associated with spatial and navigational skills. There was also a positive correlation between how long they had been in the job and how pronounced the structural difference was.

What is functional recovery?

A form of plasticity where the brain is able to redistribute or transfer functions usually performed by damaged areas to other undamaged areas following trauma. This is most likely when the brain is still maturing.

What happens in the brain during functional recovery?

The brain can form new synaptic connections close to the area of damage. Secondary neural pathways that would not typically be used to carry out certain functions are unmasked to enable functioning to continue. This process is supported by a number of structural changes e.g.:

• axon sprouting- new nerve endings grow and connect with undamaged areas

• reformation of blood vessels

• recruitment of homologous areas on the opposite hemisphere

Research support for brain plasticity.

Kuhn et al 2014 found a significant increase in grey matter in various regions of the brain after ppts played video games for 30 minutes a day over a two month period. This highlights the idea of plasticity and the brains ability to adapt as a result of new experience.

Research support for functional recovery.

Taijiri et al 2013 found that stem cells provided to rats after brain trauma showed a clear deployment of neuron-like cells in the area of injury. This was accompanied by a solid stream of stem cells migrating to the brain site of injury. This demonstrates the ability of the brain to create new connections using neurons manufactured by stem cells.

What is a weakness of plasticity?

Plasticity can have negative behavioural consequences.

Evidence has shown the the brains adaptation to prolonged drug use leads to poorer cognitive functioning in later life, as well as increased risk of dementia. Also 60-80% of apmutees develop phantom limb syndrome thought to be due to cortical reorganisation in the somatosensory cortex after limb loss.

This suggests that the brains ability to adapt to damage is not aways beneficial.

What is a strength of plasticity.

Led to practical applications i.e. the development of neurorehabilitation which uses motor therapy and electrical stimulation of the brain to counter the negative effects and deficits in motor and cognitive functions.

For example, constraint induced movement therapy is used with stroke patients where they practice using the affected part of the body while the unaffected arm is restrained.

This demonstrates positive application of research to help improve cognitive functions of people suffering from injuries.

What is hemispheric lateralisation?

The idea that the two halves of the brain are functionally different and each hemisphere has functional specialisations e.g. left dominant for language, right dominant for visual motor tasks.

Split brain research- Sperry and Gazzaniga 1967.

Aim: to examine the extent of hemispheric lateralisation.

Method: used 11 epileptics who had already had their corpus callosums split (so split brain) to conduct a quasi experiment. When info is presented to one hemisphere in a split brain patient it is not transferred to the other hemisphere. So, projected an image/word to the patients left visual field (processed by right hemisphere) or the right visual field (processed by left hemisphere).

Findings: when picture presented to right visual field, patients could describe what they saw but when presented to left visual field patient could not describe what was shown and often reported there was nothing present. when object placed in right hand, patients could describe verbally what they felt but could not when object placed in left hand. when picture presented to right visual field, while the right hand would attempt to draw a picture, it was never as clear as the left hand. when picture presented to left visual field, the left hand would consistently draw clearer and better pictures than the right hand.

Conclusion: left hemisphere is dominant in terms of speech and language whilst right hemisphere is dominant in terms of visual motor tasks.

What is a weakness of lateralisation?

Language may not be restricted to the left hemisphere.

Turk et al 2002 discovered a patient who suffered damage to the left hemisphere but developed the capacity to speak in the right hemisphere, eventually leading to the ability to speak about the information presented to either side of the brain.

This suggests that perhaps lateralisation is not fixed and that the brain can adapt following damage to certain areas e.g. functional recovery- recruitment of homologous areas.

How is age differences a weakness of lateralisation?

Lateralisation changes with age

Szaflarki et al 2006 found that language became more lateralised to the left hemisphere with increasing age in children and adolescents, but after the age of 25, lateralisation decreased with each decade of life.

This raises questions about lateralisation such as whether everyone has one hemisphere that is dominant over the other and whether this dominance changes with age.

Methodological evaluation of Sperry -split brain research

In real life the split brain patients can adjust their visual position so information goes to both hemispheres. this means that it was conducted in artificial setting as images are not normally seen for 1/10 of a second through just one visual field. In real life they would have time to compensate by moving their eyes so the material is received by both visual fields allowing them to correctly identify the material, Therefore, the study lacks ecological validity.

Sample was 11 patients- may not be large enough to generalise. May be inappropriate to make lateralisation generalisations about non-epileptic brain patterns from these patients. The epileptic seizures or even the medication they had previously taken for their epilepsy could have made changes to the brain that impacted the validity of the findings.

What are biological rhythms?

Cyclical patterns within biological systems that have evolved in response to environmental influences.

What are endogenous pacemakers and exogenous zeitgebers?

Endogenous pacemakers are internal biological clocks/mechanisms that govern biological rhythms

Exogenous Zeitgebers are external factors that influence biological rhythms.

What is a circadian rhythm? give an example.

Cycles that generally occur once every 24 hours. The sleep wake cycle is an example of a circadian rhythm which dictates when humans and animals should be asleep and awake.

Research support for circadian rhythms.

Michel Siffre 1972- spent 6 months underground in a cave in Texas with no cues as to the time of day. He had food water exercise equipment and books etc. He had a telephone link to the outside world which was staffed all the time. Siffre was wired up via computer and video so that his bodily functions could be monitored all of the tome.

The findings indicated that Siffre’s bodily rhythms initially were very erratic but they soon settled down into fairly regular cycles of activity/inatcivity e.g. sleep/wake, easting etc. His daily cycle that he established seemed to run to 25 hours rather than 24 which meant that when he emerged from his period of isolation he ‘lost’ a considerable number of days. He believed it was the 151st day when it was actually the 197th day meaning he had lost 28 days.

This suggests there is internal control of the circadian rhythm, since even in the absence of external cues we are able to maintain a semi regular daily cycle. The findings also suggest that his 24 hour sleep wake cycle was increased by the lack of external cues, making him believe one day was longer than it was which highlights the impact of external factors on bodily rhythms.

What are the strengths of research into circadian rhythms?

• shift workers experience a period of reduced concentration at around 6 am called a circadian trough. There are also links between shift work and poor health e.g. they are three times more likely to develop heart disease. Therefore, research into the sleep wake cycle may have economic implications in terms of how to best manage worker productivity e.g. many shifts start and end at 6 am to avoid circadian trough in tired workers.

• Circadian rhythms coordinate. number of the body’s basic processes such as digestion and hormone levels. This has an effect on the action of drugs and how well they are absorbed and distributed. Research into circadian rhythms has revealed that there are certain peak timed during the day or night when drugs are most likely to be effective. This has led to the development of guidelines regarding the timing of drug dosing or range of medications e.g. anti epileptic drugs.

What are the weaknesses of research into circadian rhythms?

• There was poor control in Siffre’s study. He still had access to an artificial light source which he turned on every time he woke up until he went to sleep. Light in this instance acts as a confounding variable as psychologists have argues that artificial light also has an effect on biological rhythms, meaning Siffre’s findings are questionable and lack credibility.

• Studies into the sleep wake cycle tend to use small samples or one ppt. The people involved may not be representative of the wider population. This therefore limits the extent to which these studies meaningful generalisations. Furthermore Siffre observed that his own internal bodily rhythm slowed down by the time he reached 60 meaning age is also a factor to be considered when drawing conclusions.

• However, it is important to note individual differences when it comes to circadian rhythms. Duffy et al 2001 found that morning people prefer to rise and go to bed early about 6am and 10pm whereas evening people prefer to wake and go to bed later about 10 am and 1 am. This demonstrates that there may be innate individual differences in circadian rhythms which suggests that researchers should focus on these differences during investigations.

What are infradrian rhythms and give an example.

Cycles that occur less than once every 24 hours e.g. the menstrual cycle, a monthly infradrian rhythm which is regulated by hormones that either promote ovulation or stimulate the uterus for fertilisation.

Research study into infradrian rhythms.

McClintock 1998- Sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised. This suggests that the synchronisation of menstrual cycles can be affected by pheremones which have an effect on people nearby rather than on the person producing them.

What are the positive evaluation points of infradrian rhythms?

• Research suggests that the menstrual cycle is to some extent governed by exogenous zeitgebers. Reinberg 1967 examined a woman who spent three months in a cave with only a small lamp to provide light. Reinberg noted that her menstrual cycle shortened from 28 days to 25.7 days. This result suggests that the lack of light in the cave affected her menstrual cycle and therefore this demonstrates the effect of external factors on infradrian rhythms.

• Evolutionary psychologists claim that the synchronised menstrual cycle provides an evolutionary advantage for groups of women. the synchronisation of pregnancies mean that childcare can be shared among multiple mothers who have children at the same time. these findings indicate that external factors must be taken into consideration when investigating infradrian rhythms and that perhaps a more holistic approach should be taken as opposed to a reductionist approach that considers only endogenous influences.

What are the negative evaluation points of infradrian rhythms?

• research into biological rhythms is deterministic. researching bio rhythms such as the menstrual cycle has led to a deterministic understanding of behavioural changes associated with pre menstrual syndrome. this determinist argument has been used in court to defend women against charges of murder (Johnson). On the other hand, there is evidence that bio rhythms can be influenced by free will e.g. Born et al 1999 found that people who will themselves to wake up earlier than usual had higher levels of ATCH in their blood (which is part of the waking up cycle). Therefore, showing free will over our internal rhythms.

• There are many other factors that may affect the menstrual cycle such as stress and changes in diet and exercise. these may act as confounding variables which mean that any supposed pattern of synchronisation is no more than would be expected to occur by chance. This suggests that menstrual synchrony is flawed.

What are ultradian rhythms and give an example.

Cycles that occur more than once every 24 hours. e.g. stages of sleep. this cycle altnerates between REM and NREM sleep and consists of five stages. The cycle starts at light sleep, progressing to deep and then REM sleep where brain waves speed up and dreaming occurs. This repeats itself about every 90 minutes throughout the night.

What are the positive evaluation points of ultradian rhythms?

• there is research support for ultradian rhythms. Dement and Klietmen researched 9 adults, 7 male, 2 female in a sleep lab looking at the relation of eye movement during sleep to dream activity. They found that all ppts experienced several periods of REM signified by faster EEG patterns. In REM sleep dream recall was 80% where in nREM sleep recall was 7%. They concluded that stages of sleep follow a typical pattern through the night e.g. most dreaming occurs during REM sleep.

• Ultradian research has led to an improved understanding of age related changes in sleep. Sleep scientists have identified that deep/slow wave sleep reduced with age. this may explain various issues in old age such as reduced alertness. therefore, in order to increase deep sleep relaxation and medication may be used which suggest that research findings into ultradian rhythms has practical value.

What are the negative evaluation points of ultradian rhythms?

• the way in which such research is conducted may tell us little about ultradian rhythms in humans. when investigating sleep patterns, ppts must be subjected to a specific level of control and be attached to monitors that measure such rhythms. this may be invasive for the ppt, leading them to sleep in a way that does not represent their ordinary sleep cycle. This means that research may lack ecological validity which could lead to false conclusions being drawn.

• case studies indicate the flexibility of ultradian rhythms. Randy Gardener remained awake for 264 hours. while he experienced numerous problems such as blurred vision and disorganised speech, he coped rather well with the massive sleep loss. after this experience randy slept for 15 hours and over several nights he recovered only 25% of his lost sleep. interestingly, he recovered 70% of stage 4 sleep, 50% of his REM sleep and very little of the other stages. These results highlighted the large degree of flexibility in terms of different stages within the sleep cycle.

What is an example of an endogenous pacemaker.

The superchiasmatic nucleus (SCN) which is a tiny cluster of nerve cells in the hypothalamus. The SCN obtains information about light from the optic nerve and then signals the pineal gland to increase melatonin at night. light stops the production of melatonin and dark increases production of melatonin.

What are some examples of exogenous zeitgebers?

Light is the most dominant zeitgeber in humans as it can reset the SCN. Light also has an indirect influence on key processes such as hormone secretion and blood circulation.

Social cues can also be a zeitgeber e.g. our sleep patterns are based on our age and daily routines, they appear the be entrained by social convention.

Finally temperature becomes the dominant zeitgeber in the absence of light. Cold signals a time for reduced activity and warm is the time for activity.

What are some strengths of endogenous pacemakers and exogenous zeitgebers?

• DeCoursey et al 2000 removed the SCN in 30 chipmunks. the chipmunks were returned to their natural habitat and observed alongside normal chipmunks. After 80days significantly more of the SCN lesioned chipmunks had been killed by weasels. This was presumably because these chipmunks remained awake and vulnerable when they should have been asleep. This study emphasises the role of the SCN in establishing and maintaining the sleep/wake cycle.

• Further research comes from Morgan 1995 who bred ‘mutant’ hamsters so they had circadian rhythms of 20 hours instead of 24 hours and then transplanted their SCNs into normal hamsters. The normal hamster then displayed the mutant rhythms. This study again emphasises the role of the SCN in establishing and maintaining the sleep wake cycle.

What are the weaknesses of exogenous zeitgebers and endogenous pacemakers?

• studies of the individuals who live in the arctic regions where the sun does not set during the summer months show normal sleep patterns despite the prolonged exposure to light. This suggests that there may be occasions when exogenous zeitgebers may have little bearing on our internal rhythm. This is known as free running where the bio clock operates in the absence of any external cues.

• When using animal studies, we should consider that humans are more complex than hamsters or chipmunks therefore, we should be cautious generalising the findings from animal studies to the human sleep wake cycle.