BIOPSYCHOLOGY

LOCALISATION OF FUNCTION IN THE BRAIN

Phineas gage

he was playing with explosives on a railroad track. a metal pole pierced through his eye into the frontal lobe. he started to become aggressive and rude

two hemispheres - left and right

left hemisphere controlled the right side of the body and vice versa

cerebral cortex - 3mm thick layer on the outside of the brain.

exam question - using an example, explain what is meant by ‘localisation of function’

localisation of function also known as cortical specialisation is the idea that different parts of the brain have different function and perform different tasks. so if a section of the brain is damaged by injury or illness some functions and emotions may be effects. this is shown in the case of Phineas gage who was pierced in the brain with a large metal pole, it went through his frontal lobe and family members observed a change in his behaviour and described him as being more aggressive and rude.

the brain is divided into 2 hemispheres

left is analyser

right is synthesiser

they are joined by the corpus callosum

this is made up of network of fibres

its function is to communicate between hemispheres

the brain is contralateral this means that each hemisphere controls the opposite side of the body.

one example of this is that the left hemisphere controls the right hand

cerebral

cortexes

somatosensory cortex - located in the parietal lobe. separated from the motor area by the ‘central sulcus’. where sensory information on the skin is processed and represented in the brain. the somatosensory cortex is representative of different areas to different extents. each area is devoted to a different body part. the hands and face make up the majority of the somatosensory cortex.

motor cortex - back of the frontal lobe. controls voluntary movements. the right controls the left side of the body’s fine movement, the left controls the right. damage to this area of the brain can lead to the loss of the fine motor skills, e.g. makeup, writing, earrings

auditory cortex - found in the temporal loves in both hemispheres. speech based information. cochlear - brain stem - thalamus - auditory cortex. damage could case partial hearing loss.

visual cortex - found in the occipital lobe of the brain and focuses on vision. the right visual field signals to the left visual cortex and vis versa. damage to the left side could result in blindness to both visual fields.

LOCALISATION OF FUNCTION IN THE BRAIN: LANGUAGE CENTRES

stroke patients

expressive aphasia - sara scott

produce the words struggle - can write/remember.

in the 1880’s Broca identified an area linked to speech production.

damage to this area causes ‘Broca’s aphasia’ which is speech that is slow, labourious and lacking in fluency.

case study - tan. named tan because Broca’s damage meant ‘tan’ was the only thing he could say

bryan peterson - wernekes aphasia

knows what he wants to say but words get mixed up possibly with things that sound similar or mean similar things.

Carl Wernicke discovered this region as he noted people who could produce speech but struggled to understand it.

these people could produce fluent speech but it had no meaning.

damage results in ‘Wernickes aphasia’ if damaged. this often means patients will add nonsense words to speech.

parietal lobe - somatosensory - both

temporal - auditory cortex - both

temporal - Wernikes’s area - left hemisphere

occipital - visual cortex - both

frontal - Broca’s area - left hemisphere

frontal - motor - both

outline the role of Broca and Wernicke’s area’s within the brain.

Broca’s area is located in the frontal lobe and is responsible for speech production. damage to this area causes aphasia which is characterised by slow speech that is laborious and lack fluency. there was a case study on this and it was done on a patient called tan who was only able to say his name. people with Broca’s aphasia often have difficulty with prepositions and conjunctions. Wernicke’s are is located in the left frontal lobe and is responsible for language understanding. if the area is damaged it results in Wernicke’s aphasia which is when people produce nonsense words.

name the 4 lobes of each hemisphere in the brain.

frontal, parietal, temporal, occipital

what is meant by the term ‘localisation’ of function.

different parts of the brain control different functions and parts of the body.

outline the difference between localisation and lateralisation of function in the brain.

hemispheres have different functions. different areas of the brain have different behaviours, processes or activities.

complete the table

hearing - auditory cortex

understanding what the teacher says - Wernicke’s area

speaking to an assistant in a shop - Broca’s area

sensing something is hot to the touch - somatosensory area.

evaluation -

Phineas gage - drastic personality changes after an accident - frontal lobe was effected. support

Tulving - semantic and episodic memories focused in different sides of the pre-frontal cortex. support

Peterson and Peterson - Wernecki’s was active during listening, Broca’s active during reading. support

Lashly - removed 10-50% of rats brain matter and got them to do a maze he found that no matter how much brain is removed they went and did the maze the same. more holistic brain processing.

HEMISPHERIC LATERALISATION

lateralisation of the brain refers to the concept that the two hemispheres of the brain have different functionality

the processes involved in the brain differ dependent on the side of the brain, as processes are lateralised.

for example, language is in the left hemisphere of the brain so it is lateralised.

Sperry - split brain research

• aimed to show that the hemispheres of the brain had certain functions

• he studied patients who had received an operation to cut their corpus callosum to control epileptic seizures

• as a result, information from one hemisphere couldn’t be communicated to other for processing

• this allowed researchers to assess the function of each hemisphere.

outline the main aspects of the procedure

there were 11 split brain participants. it was a Quasi experiment. the experiment involved comparing the performance of 11 split brain participants on various different tasks with the performance of people who didn’t have a split brain lateralisation. he used a number of different tasks in order to investigate the lateralisation of brain function. the tasks were carried out in lab conditions, using specialised equipment and everything was highly standardised.

one of the tasks used to send information to one hemisphere was how participants responded to visual information. this involved blindfolding one of the participants eyes and asking to fixate with the seeing eye at the point on the middle of the screen. they would then project a stimulus on the screen for less than 1/10th of a second.

LATERALISATION OF FUNCTION AND SPLIT BRAIN RESEARCH: EVALUATION

STRENGTH

lateralisation in the normal brain - fink used pet scans to identify which brain areas were active during visual processing tasks when non split brain research participants were asked to attend to global elements of an image such as an image of a forest. regions of the RH were more active but when looking in finer detail the LH was more active.

LIMITATION

One brain

the idea of the LH being an analyser and the RH being the synthesiser might be wrong. there might be different functions of the different hemispheres but research suggests that people do not have a dominant half. Nielsen analysed brain scans from over 1000 people aged 7 to 29 and they found that people used certain hemispheres for certain tasks but there was no evidence of a dominant side.

EVALUATION EXTRA

Lateralisation vs plasticity

Lateralisation is adaptive because it enables two tasks to be performed simultaneously. rogers showed that chickens that were lateralised could find food whilst watching for predators but non lateralised chickens couldn’t. on the other hand, neural plasticity could also be seen as adaptive. following damage through injury or trauma, some functions could be taken over by the opposite hemisphere so language could swap sides.

STRENGTH

research support

Gazzaniga showed that split brain participants actually perform better on normal controls on certain tasks. e.g they were faster at spotting the odd one out from an array of similar objects. which supports Sperry’s earlier findings.

PLASTICITY AND FUNCTIONAL RECOVERY OF THE BRAIN AFTER TRAUMA

PLASTICITY

refers to the brains ability to adapt both physically and functionally, in response to experience and new learning.

Gopnik: connections in babies brains.

during infancy, the brain shows rapid growth in the number of synaptic connections

at the age of 2-3 years the number of these peaks at 15000

this is twice as many as there are in the adult brain. the difference is the result of processes called synaptic preening.

evidence to show plasticity in the brain

1. Maguire 2000: London taxi drivers

studied the brains of London taxi drivers and found significantly more volume of grey matter in the posterior hippocampus than in a matched control group. this part of the brain is associated with development of spatial and navigational skills. as a part of their training they must take a complex test which assesses their recall of the city streets and their possible routes. they found that the longer they have need a driver the more pronounced of a difference in brain structure.

2. Draganski 2006: med students

he imaged the brains of medical students three months before and then 3 months after their final exam. learning induced changes were seen to have occurred in the posterior hippocampus.

3. mechelli 2004: bilingual brain

found a larger parietal cortex in the brains of people who were bilingual in conparason to people who are monolingual.

FUNCTIONAL RECOVERY