Left hemisphere

Most people, language processing is here

Focuses on detail

Right hemisphere

Recognising such as recognising emotions of others

Spatial relationships - Clarke, Assal and de Tribolet- found that a woman got lost in familiar places however if given verbal instructions she did not get lost.

Focuses on patterns

Motor cortex

Causes movement

Sends messages through the brain stem and spinal chord to the muscles

Important for complex movemeents such as running but not basic movements such as coughing

Motor cortex instructs the body on a specific outcome however the spinal chord and other areas of the body co-ordinate the body's movement in relevant areas

Areas of the brain involved in movement- spinal chord and brain (co-ordinate movement), premotor cortex (plans a movement before it is done) and the prefrontal cortex (stores sensory information before the moevement and works out the likelihood of the movement outcome

Somatosensory cortex

Makes sense of external information from our senses

2 parts to the sensory cortex- primary sensory cortex where the brain first processes information from sensory organs and the second sensory cortex which is involved in higher order processing needed for hand-held objects

Amount of neural connections needed to the somatosensory cortex in specific areas is dependent on the amount of the somatosensry cortex needed in that specific area e.g. face would need a lot however trunk of the body would need very little.

Visual centres
Primary visual cortex

In the occipital lobe

Main visual area

An area within the main visual area called Area V1 is seen to be very important for visual perception

Receives and processes sensory nerve impulses from the eyes

Those with damage in V1 are said to not have any vision including conscious vision, dreams or visual imagery while awake (Hurrovitz et al- 1999)

Visual information is transmitted along 2 pathways- 1 is components of the visual field and the other is to do with locations within a visual field

Individuals with Are V1 damage can have 'blindsight'. This is where someone appears blind as they do not have vision but they can find objects within a visual field by pointing. Shows how some processing in the visual cortex may not be conscious (Bridgeman and Staggs- 1982)

Auditory centres
Primary auditory cortex

2 primary auditory cortices, one in each hemisphere

Converts sound waves from our ears into understandable data by electric impulses

Auditory cortex in both hemispheres receives information from both ears via 2 pathways that transmit information about what a specific sound is and the location of the sound

Information from the right ear mainly goes to the left hemisphere but some is transmitted to the left primary auditory complex too (happens in the same way to the left ear)

Primary auditory cortex damage does not lead to total deafness as sounds can still be heard but sounds that need complex processing such as music cannot be heard

Primary cortex also processes auditory image- when individuals watch silent films the primary auditory cortex in both hemispheres of the brain was activated e.g. if a door was shut with force as the 'bang' that would go with the closing of the door had been imagined

Disorders due to damage to this area include classical auditory agnosia (inability to process environmental sounds such as animal noises)

Language centres
Broca's area

Speech production

Not all words are equally affected if there is damage to this area of the brain- nouns and verbs seem to be unaffected in some patients with Broca's area damage and other word categories such as prepositions and conjunctions (e.g. and, if, but) are unable to be spoken e.g. cannot read out 'to be or not to be' but can read put 'two bee oar knot two bee' (Gardner and Zurif- 1975)

Louis Leborgne suffered from epilepsy and eventually was unable to speak other than to say the word tan. Following his death, Broca (a neurologist treating Leborgne before his death) found a lesion (area which has damage) on the left temporal lobe. It was the only area of the brain with visible damage so Broca concluded this was the area involved with speech production. Since then Leborgne's brain has been scanned using modern techniques and although there is more extensive damage the area of the brain Brocca found for speech production was correct

Disorders associated with damage in this area include stuttering (underactivity in the area)

Language centres
Wernicke's area

Separate area of language processing

Understanding language and assessing words

Found by Wernicke who found that those with damage in the area were unable to comprehend language and struggled to find the words they needed but could speak fluently

Case study- Phil had a stroke and was unable to speak in understandable language as the Wernick's area of the brain was damaged. He suffered from Wernicke's aphasia

Evaluation of research into localisation of function

Helps understand people's injuries when brain damage occurs

Help to find new treatments and cures for illnesses and disorders caused by damage to a specific area of the brain

Can be scientifically studied in a controlled environment

Can be studied using scientific equipment

There are few cases that can be studied to find the localisation of function

Case studies are often outdated

Lashley found that on rats' brains there was no specific area involved with memory and it seems memory is stored all over the brain. However caution should be taken when applying this to humans as there are differences physiologically

Evidence from case studies suggests there is locationalisation and lateralisation of functions. If functions were all over the brain then specific defects would not occur

Case studies only give evidence and cannot provide proof

Split brain research

To help individuals with epilepsy that cannot be controlled with drugs the area of the brain associated with the epilepsy can be removed

If there are several areas of the brain which are causing the epilepsy the corpus callosum can be cut so that the epilepsy is contained within one hemisphere. This reduces the number of epileptic fits as it stops the hemispheres rebounding from each other which can prompt seizure

This method of 'splitting the brain' can reduce epileptic fits but can affect behaviour and perception

Alien-hand syndrome

Where the 2 hemispheres are in competition between parts of the brain

The feeling that an individual has that their hand is possessed by a force outside of their control, they can feel sensation in their hand but believe the hand is not a part of their body and have no control over their movement

The right side of the brain is usually dominated by the left side of the brain, but in this case the right side refuses to be dominated by the left e.g. left hand may tie the shoelaces and right hand untie the shoe laces without an individual realising

Split brain research- Richard Sperry- 1974

Aim
To investigate the hemispheric functioning of split-brain patients

Procedure

Quasi-experiment

11 participants who all had had their corpus callosum severed

Performed tasks and the results were compared with those who had their corpus callosum intact

The tasks involved presenting information to one hemisphere by sending it to 1 visual field so they were blindfolded so only one eye recieved the information

Findings

Information shown to 1 hemisphere can only be recalled if shown to that hemisphere again

Visual information shown to the left hemisphere (right visual field) can be described in speech

Visual material shown to the right hemisphere (left visual field) will deny seeing anything but are able to pick the correct object out with their left hand

2 different figures shown to the hemispheres, the participants could draw what they had seen in the left visual field with their left hand (right hemisphere) but if asked what they had drawn they would say what they saw in their right visual field (left hemisphere)

Object placed in the right hand can be described or named (left hemisphere) but an object placed in the left hand cannot be described or named, only picked out from other objects (right hemisphere)

Objects can only be selected by the hand which they were originally placed

Left hand will ignore objects the right hand is looking for and vice versa

Conclusions

There is some lateralisation of function between the hemispheres

Evaluation of split brain research

Small sample size so cannot be generalised accurately

Small sample size is representative of the number of individuals who undergo the operation

High level of control and variables controlled so is scientific and valid

Research evidence

Low ecological validity as the research does not involves problems encountered normally so is an artificial setting

Cannot compare brains of severely epileptic people to normal people as the brain could be different due to the epilepsy or could be different due to surgery

Brain plasticity (ability of the brain to change and adapt synapses, pathways and structures after various experiences e.g. positive (e.g. learning) or negative (e.g. recovering after brain trauma)

Rosenzweig, Bennet and Diamond- 1972- role of environmental stimulation on brain plasticity

Aim
Investigate if environmental factors would affect development of neurones in the cerebal cortex

Procedure

Rats either in enriched condition (EC) or impoverished condition (IC)

EC researchers placed 10-12 rats in a cage with different stimulus objects to explore and play with and received maze training

IC researchers placed each rat into individual cages with no maze training or toys

Standard condition (SC) where rats were kept in a standard lab cage with food and water

Spent 30-60 days in the environment and then were killed to study the brain anatomy differences

Results

Anatomy of the brain was different between IC and EC

Higher thickness and weight in cortex of EC than IC

Rats in EC had greater activity in the neurones in the cerebal cortex which were involved with the transmission of acetylcholine (important neurotransmitter for learning and memory)

Just 2 hours a day in EC produced the same changes in rats that had been in the EC for a long period of time

Evaluation

Challenged the belief that brain weight cannot change

Controlled environment

Animals used so could be hard to generalise to humans

Replicated a number of times so is reliable

Ethical issues with the use of animals

Case study: Jody Miller

Aged 3 she started having frequent seizures from her right hemisphere that were nearly fatal

Had to have the right hemisphere removed

Plasticity of the brain enabled the left hemisphere to take over some of the right hemisphere functions so Jodie was now able to walk (previously she had difficulty doing this)

Neurone plasticity

Axonal sprouting- when an axon is damaged the connect between the neighbouring neurone is lost. Some cases the other axons connected to the neurone will create extra connections to the neurone to replace connections lost from the damaged axon. Occurs for about 2 weeks after damage and will only work if the damaged and compensatory axons have similar functions

Growth of new neurones (neurogenesis)- occurs in the human olfactory bulb and hippocampus. Not yet known how this helps

New behavioural strategies- Not direct recovery of function but is about using other means to have the function e.g. memory loss so writing down memories and not relying on your memory. Kaspar- 1997- recovery after brain damage is better in doctors this could be due to them having greater cognitive resources to draw on and leads them to develop better alternative starategies

Denervation supersensitivity- axons that do a similar job become more aroused so that they can compensate for axons lost. It can cause consequences such as over-sensitivity to messages such as pain

Evaluation of plasticity research

Tested on animals sometimes so is not representative

Not a large population size

Lots of different research has been done

How the brain attempts to recover

Drugs- chemicals in the brain can help control brain growth and organisation of neurones in the developing brain. Some of the chemicals it is hoped, could be used after damage to prevent the degeneration and death of neurones and increase regeneration and axon sprouting

Neuron transplant- new area. Stem cells implanted into a damaged area have the potential to grow into neurones and make functional synaptic connections to help to restore behavioural functions

Rehabilitation and brain re-organisation- practising skills can alter the brain's organisation, so practice of a skill affected by brain damage may lead to significant recovery

Evaluation

Not a large population size

Effects are seen under controlled environments not real life situations

Different researchers have studied this

Could have bias effects with medicine

Hard to know how much it has recovered as often functioning before the injury is not known

Hard to make generalisations of recovery as each individual is different and recovery varies according to the extent of damage and localisation

Factors affecting brain recovery

Perseverance- function may be lost but that could be due to the individual not properly trying and believes it is unable to be recovered

Physical exhaustion, stress and alcohol consumption- Stress and alcohol consumption can affect the ability an individual has to use a function which has been regained. When function of an individual is recovered it has to be remembered that often the function is used with lots of effort and means the person can do the task but are often fatigued by it

Age- deterioration of the brain during old age can affect the extent and speed of recovery.

Gender- research suggests women can recover better from brain injuries as their functions are not as lateralised (concentrated in 1 hemisphere). However there are mixed views on women recovering better from brain injuries so no overall conclusions can be made

	Created by Ella Broomer over 7 years ago

AQA Psychology A level