hemispheric lateralisation and split brain research- biopsychology Flashcards
what is localisation and lateralisation
localisation refers to fact that some functions are governed by specific areas in the brain
lateralised there are two sides which are called hemispheres
what is the left and right hemispheres
two main centres- brocas area left frtonal lobe and wernickes area is left temporal lobe
language is lateralised performed by one hemisphere rather than the other
the rh can only produce rudimentary words and phrases but contributes emotional context
led to suggestion that lh is the analyser whilst rh is synthesiser
many functions not laterlised, there is a further twist in the case of the motor area the brain is cross wired
rh controls movement on the left sde of the body whilst the lh cntrols movement on the right
vision- both contralateral and ipsilateral, each eye receives light from the left visual field and the right visual field
lvf of both eyes connected to rh and the rvf of both eyes connected to the lh, enables visual areas to compare slightly different perspective from each eye and aids depth perception
similar arrangement for auditory input to the auditory area and the disparity from the two inputs helps us locate source of sounds
what is lateralisation in the connected brain
strength- research showing that even in connected brains two hems process info differently
fink used pet scans to identify which brain areas were active during visual processing task
pps connected brains were asked to attend global elements of image
when required to focus in on final detail specific areas of the lh tended to dominate
suggests visual proceedings concerned hemispheric laterlisation is feature of the connected brain as well as split brain
what is one brain
weakness- lh as analyser and rh as synthesiser may be wrong
may be different dunctions in rh and lh butbresearch suggests people do not have dominant side of their brain which creates different personality
nielsen analysed brain scans from over 1000 people aged 7-29 and did find that people used certain emispheres for certain tasks
no evidence of dominant side
suggests otion of right or left brained people is wrong
what is lateralisation versus plasticity
lateralisation adaptive as enables two tasks to be performed simultaneiusly with greater efficieny
rogers showed that lateralised chickens could find food while watching for predators but normal chickens couldnt
plasticity could be seen as adaptive
following damage through illness or trauma some functions cna be taken over by non specialised areas in the opposite hemisphere
language function an switch sides
what is research support
strength- support from more recent split brain research
gazzaniga showed split brain pps perform better than connected controls on certain tasks
they were faster at identifying odd one out in array of similar objects than normal controls
normal brain lh better cognitive strategies watered down by inferior rh
supports sperrys earlier findings that the left brain and the right brain are distinct
what is generalisation issues
weakness- sperrys research casual relationships hard to establish
behaviour of sperrys split brain pps compared to neurotypical control gorup
issue though is that none of pps in the control group has epilepsy
mjaori confounding variable
any differences observed between two groups may be result of epilepsy rather than split brain
means that some of unique features of split brain pps cognitive abilites might have been due to epilepsy
what is ethics
split brain operation not performed for purpose of research
sperrys pps not deliberately harmed
all procedures explained to split brain pps and their full informed consent obtained
trauma of operation might mean that the pps did not later fully understand the implications of what they had agreed to
subject to repeated testing over legnthy period and this may have been stressful over time
