hemispheric lateralisation

• lateralisation = one hemisphere of the brain being responsible for specific physical and psychological functions

  hemispheres process info contralaterally e.g damage to left hemisphere damages right side of the body.

  hemispheres are connected by the corpus callosum

  language centres are usually located in the left hemisphere of the brain
• epilepsy

  in individuals with severe epilepsy they can undergo 'split brain' operation where the individuals undergo a commissurotomy to keep severe seizures in one hemisphere.
• SPERRY R

  investigated 11 patients with epilepsy who underwent a commissurotomy. they had to look at a dot in the middle of a screen and a word/object would flash up

  if processed in the left hemisphere, patients could say word/object out loud but not draw/write it. if processed by the right hemisphere patients couldn't say word but they could write/draw it and select it out of a list of other objects/words. this is because language hemispheres are in the left hemisphere, while visual spatial centres are in the right hemisphere. concluded that hemispheres are independent to one another
• A03

  + sperrys research was pivotal in distinguishing the differences between the two hemispheres, therefore rejecting a holistic approach. research found that the left hemisphere is more language based while the right hemisphere is responsible for visual spatial tasks. therefore, this demonstrates left hemisphere as analyser while right hemisphere is synthesiser, thus establishing distinct differences between the two. this is vital in helping diagnose and understand cognitive conditions such as strokes.
• A03

  -lack of control within selected sample. all epileptic patients were on anti-epileptic medication for different periods of time which may have altered ability to identify words/objects. similarly, while all patients had undergone a commissurotomy there were differences in the degree of extent of lesions in the corpus callosum. therefore this would've affected the extent to which the two hemisphere relayed information to each other. therefore this lack over huge confounding variables means false causal conclusions may have been recorded.
• A03

  -small sample size - the use of only 11 patients means that there would be individual differences present that can alter the validity of the results. furthermore, the control group were neurotypical people that didn't have epilepsy. therefore this makes it hard for cause and effect relationships to be established as the control, group doesn't act as a valid baseline to compare commisurotomy patients to.