biopsych

• Localisation of function


  theory that different areas of the brain are responsible for different behaviours, processes or activities
• Brain structure

  
• hemispheres of the brain & the cerebral cortex

  The brain is divided into 2 symmetrical halves called left&right hemispheres. outer layer is cerebral cortex like a tea cosy covering the inner parts of the brain. cortex appears grey
• cerebral cortex

  outer layer is cerebral cortex like a tea cosy covering the inner parts of the brain. cortex appears grey due to the location of the cell bodies.
• Somatosensory area


  front of both parietal lobes.

  Where sensory information from the skin (e.g related to touch, heat, pressure, etc) is represented
• Motor area


  Back of the frontal lobe.

  Controls voluntary movements in opposite side of the body.
• Visual area


  In the occipital lobe at the back of the brain.

  each eye sends info from the right visual field to the left visual cortex and opposite.

  damage to the left hemisphere, can produce blindness to the right visual field of both eyes.
• auditory area


  in the temporal lobe.

  analyses speech-based information.

  damage may produce partial hearing loss.
• broca's area


  Language=left hemisphere.

  small area in left frontal lobe responsible for speech production.

  Damage causes Broca's aphasia= slow, influent speech (like in Tan).
• Wernicke's area


  in left temporal lobe.

  responsible for language comprehension.

  result in wernicke's aphasia when damaged- often produce nonsense words as part of the content of their speech.
• localisation of function- strengths


  -LTM study by Tulving revealed semantic and episodic memories are located in different parts of the frontal cortex. There now exists a number of sophisticated&objective methods for measuring brain activity, providing sound evidence of localisation.

  -surgically removing areas of the brain to control aspects of behaviour developed in the 1950's- were brutal and imprecises. a study reported on 44 OCD patients who had a cingulotomy. At a 32 week follow up, 1/3 met the criteria for successful response to surgery&14% for partial response. success suggests symptoms and behaviours associated with serious mental disorders are localised.

  -unique cases of neurological damage support localisation theory, e.g Phineas gage in accident. he survived by the damage to his brain affected his personality. the change in gage's temperament following the accident suggests the frontal lobe may be responsible for regulating mood.
• localisation of function- negatives

  -Lashley suggests higher cognitive functions are not localised but distributed in a more holistic way. Lashley removed between 10&50% of rats cortex when they were learning a maze. no area was more important than another in their ability of learning the maze. suggests learning is too complex to be localised and involves the whole of the brain.

  -when brain is damaged and function compromised or lost, rest is able to reorganise itself to recover the function.
• Plasticity


  The brain's tendency to change and adapt as a result of experience and new learning.

  during infancy, the brain has around 15000 synaptic connections at age 2-3 years.
• synaptic pruning


  as we age, rarely used connections are deleted and frequently used connections are strengthened.
• Research into plasticity

  Maguire: studied brains of london taxi drivers and found more volume of grey matter (cerebral cortex) in the posterior hippocampus than in a matched control group. area is associated with the development of spatial and navigational skills in humans and other animals. The longer they had been in the job, the more pronounced the structural difference.

  Draganski: imaged brains of medical students 3 months before and 3 months after final exams. learning induced changes were seen to have occured in posterior hippocampus.
• Functional Recovery

  a form of plasticity. following damage through trauma, the brain's ability to redistribute or transfer functions usually performed by a damaged area to other undamaged areas.
• what happens to the brain during recovery?

  brain is able to rewire and reorganise itself by forming new synaptic connections close to the area of damage.

  -axonal sprouting- growth of new nerve endings which connect with other undamaged nerve cells to form new neuronal pathways.

  -reformation of blood vessels

  -recruitment of homologous (similar) areas on opposite side of the brain to perform specific tasks.
• plasticity and functional recovery- strengths

  -has contributed to the field of neurorehabilitation. techniques include movement therapy and electrical stimulation of the brain to counter deficits to cognitive functioning experienced following a stroke. shows that although the brain may have the capacity to fix itself, this process requires further intervention if it is to be successful.

  -hubel sewed one eye of a kitten shut and analysed the brains cortical responses. the area of the visual cortex associated with the shut eye was not idle but continued to process info from the open eye. demonstrates how loss of function leads to compensatory activity in the brain- evidence of neural plasticity.
• plasticity and functional recovery- negatives

  -brains ability to rewire itself can have maladaptive behavioural consequences. 60-80% of amputees develop phantom limb syndrome- continued experience of sensations in the missing limb, usually painful. suggests the structural and physical processes involved in functional recovery may not always be beneficial.

  -functional plasticity tends to reduce with age. the brain has a greater propensity for reorganisation in childhood as it constantly adapts to new experiences and learning. Bezzola demonstrated how 40 years of golf training produced changes in neural representation of movement in p's age 40-60.

  -persons educational attainment may influence how well the brain functionally adapts after injury. Schneider found the more time brain injury patients had spent in education, greater chances of disability free recovery. cognitive reserve is a crucial factor in determining how well the brain adapts after trauma.
• Split brain research

  a series of studies began in 1960s involving epileptic patients who had experienced a surgical separation of the hemispheres of the brain. Allowed researchers to investigate the extent to which brain function is lateralised.
• Hemispheric Lateralisation

  the idea that the 2 halves of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other.
• split brain studies- Sperry

  Sperry- unique group of people who had their corpus callosum which connect the 2 hemispheres. main communication line between the 2 hemispheres was removed.
• Split Brain Studies- Sperry procedure

  general procedure image or word could be projected to a patients right visual field (processed by left hemisphere), and same image could be projected to the left visual field (processed by right hemisphere). In normal brain, the corpus callosum would immediately share the information between both hemispheres giving a complete picture of the visual field.
• Sperry findings- describe what you see

  Picture shown to patients right visual field, patient could easily describe what was seen. If shown to left VF, patient could not describe what was there. Language is processed in left hemisphere. Patients inability to describe objects in left visual field was because of lack of language centres in right hemisphere. In normal brain, messages from RH relayed to language centres in LH.
• Sperry findings- recognition by touch

  patients couldnt attach verbal labels to objects projected in the left VF, they were able to select a matching object from a bag of different objects using their left hand. Objects placed behind a screen. Left hand was able to select an object that was most closely related with object presented to left VF. In each case, the patient not able to verbally identify what was seen but could understand the object using the RH and select corresponding object.
• sperry findings- composite words and matching faces

  2 words presented on either side of the visual field (e.g key to the left and ring to the right). patient:

  -selects a key with their left hand (LVF goes to RH linked to left hand)

  -says the word 'ring' (RVF linked to LH with speech centres.

  composite picture made up of 2 different halves of a face was presented (1/2 to each hemisphere)

  -LH dominated the verbal description.

  -RH dominated the selection of a matching picture.
• Split brain research- positive

  -left hemisphere=analytical and verbal- the analyser and the right hemisphere=adept at spatial tasks and music- synthesiser. RH can only produce basic words and phrases but contributes emotional content to language. may be too simplified.

  -sperry used carefully standardised procedure of presenting visual information to one hemispheric field at a time was quite ingenious. image flashed up for 0.1 seconds so no time to move eyes and spread image across both sides of visual field or both sides of the brain.

  -sperrys work triggered a theoretical and philosophical debate about the nature of consciousness and the degree of communication between the 2 hemispheres in everyday functioning. pucetti suggested the hemispheres are so functionally different they represent a form of duality in the brain. others argued the 2 hemispheres are highly integrated and worked together in most tasks.
• split brain research- negatives

  -many researchers have said these findings canno be widely accepted as S-B patients are such an unusual sample of people. only 11 patients took part in all variations and all had a history of seizures. may have caused unique changes in the brain that influenced the findings. this limits the extent to which the findings can be generalised, so limiting the validity of the conclusions

  -growing body of pop psychological literature that oversimplifies and overstates the difference in function between the 2 hemispheres. modern neuroscientists argue these distinctions are not all clear cut. many behaviours that are associated with one hemisphere can be performed by the other where situations require. suggests some of sperrys conclusions may be too simplistic.
• fMRI


  functional Magnetic reasonance imaging detects changes in blood oxygenation and flow that occur due to neural activity in specific brain areas. fmri produces a 3D image showing which parts of the brain are active and therefore must be involved in particular mental processes.
• fMRI evaluation

  + it is non invasive- doesn't rely on use of radiation and is safe. It produces images with high spatial resolution, showing detail by the milimeter.

  - is expensive compared to other techniques and can only capture a clear image if the person stays still. poor temporal resolution because of 5 second lag between initial neural activity and image.
• EEG


  Electroencephalogram measures electrical activity within the brain via electrodes using a skull cap. The scan recording represents brainwave patterns generated from millions of neurones. EEG is often used as a diagnostic tool.
• EEG evaluation

  + has contributed to understanding of the stages of sleep, high temporal resolution. EEG's can detect brain activity at resolution of a single millisecond.

  - EEG produces a generalised signal from thousands of neurons. Difficult to know the exact source of neural activity.
• ERPs


  Event Related Potentials are what is left when all extraneous brain activity from an EEG recording is filtered out. This is done using a statistical technique, leaving only those responses that relate to the presentation of specific stimulus. ERP's are types of brainwave triggered by particular events.
• ERPs evaluation


  + ERP's are more specific than can be achieved using raw EEG data. Good temporal resolution.

  - lack of standardisation in methods between studies makes it difficult to confirm findings. another limitation is that background noise and extraneous material must completely eliminated. may not always be easy to achieve.
• Post Mortem Examinations


  involves the analysis of a person's brain following their death. Areas of the brain are examined to establish the likely cause of a deficit or disorder that the person suffered in life.
• Post mortem- evaluation

  + Broca and Wernicke both relied on post mortem studies. Post mortem studies improve medical knowledge.

  - observed damage may not be linked to the deficits under review but to some trauma. raise ethical issue with lack of consent before death. may not be able to provide informed consent.
• Biological rhythms governed by endogenous pacemakers and exogenous zeitgebers

  endogenous pacemakers= internal biological 'clocks'.

  exogenous zeitgebers= external changes in the environment. Some of these rhythms occur many times a day (ultradian rhythm); others take less than a day to complete (infradian rhythm) and in some cases, much longer (circannual rhythms).
• Sleep/wake cycle is governed by internal and external mechanisms

  exogenous zeitgebers- the fact we feel drowsy when its night time and alert during the day shows the effect of daylight.

  endogenous pacemakers- a biological clock 'left to it's own devices' without the influence of external stimuli e.g light is called free-running.

  There's a basic rhythm governed by the suprachiasmatic nucleus (SCN) which lies above optic chiasm and receives information about light directly from this structure. Exogenous zeitgeber (light) can reset the SCN.
• Siffre demonstrated a free-running circadian rhythm of about 25 hours


  French caver Siffre spent long periods in dark caves to examine the effects of free-running biological rhythms- 2 months in the caves of southern alps and 6 months in a Texan cave. In each case study, siffre's free running circadian rhythm settled down to just above the usual 24 hours (about 25 hours). He did have a regular sleep/wake cycle.
• Aschoff and Weaver also found a similar circadian rhythm


  A group of p's spent 4 weeks in a ww2 bunker deprived of natural light. All but one, whose sleep/wake cycle extended to 29 hours, displayed a circadian rhythm between 24 and 25. Siffre's experience and the bunker study suggest that the 'natural' sleep/wake cycle may be slightly longer than 24 hours but is entrained by exogenous zeitgebers associated with our 24-hour day.