hemispheric lateralisation Flashcards
hemispheric lateralisation definition
the idea that the 2 halves of the brain are functionally different and that each hemisphere has specific functions
how is language organised
language is lateralised (limited to one half of the brain) as broca’s/wernicke’s area is in the LH.
how is the motor area organised
contralateral (processed in opposite side of the body to the hemisphere), LH controls RHS of the body etc.
how is vision organised
Contralateral (processed in opposite sides as the RVF is received by the LH), and ipsilateral (same sided)
what was roger sperrys aim
to investigate the extent to which hemispheres were specialised
what is a commissurotomy
surgical procedure of cutting the corpus callosum down the middle)
what was sperrys general procedure
image/word appears to the LVF/RVF of a commissurotomy patient to be processed to the certain hemisphere, whilst the patient was fixated on a dot in the middle. He tested 11 males
what were sperrys tasks and findings
•describe what you see - word to the RVF the patient could describe but not for the LVF
• recognition by touch - the patients selected objects matching/semantically similar to the word flashed to the LVF with the LEFT HAND from behind a screen whilst not being able to verbally identify the word (could still ‘understand’)
sperrys overall research results
•LH verbal RH non-verbal
•RH still processes images non-verbally
•when shown ‘racey’ images to the LVF the patient ‘giggled’ - showing an emotional response despite seeing nothing, the RH processes emotions
what’re 3 strengths for Hemispheric Lateralisation
Brain Scan evidence, Adaptive advantages, Sperrys scientific/standardised work
what is 1 weakness of hemispheric lateralisation
Lack of generalisability in Sperrys work
why does sperrys work lack generalisability
split-brain patients are rare and his sample size was small with 11 males with a history of severe epilepsy. Furthermore, the severe damage from epilepsy means we cannot be sure of any underlying damage to the brains, and the control groups weren’t epileptic do comparison is difficult. Thus the lack of standardised sampling and the confounding variables of biology/brain alterations via surgery/brain storms/drugs lowers generalisability of sperrys work - a main research foundation for the theory of hemispheric lateralisation
how do brain scans support hemispheric lateralisation
Fink et al. used PET scans to identify brain activity during a visual task. when participants saw the whole picture (holistically) the RH was more active, and when focusing on specific details (a tree) the LH was dominant, showing that the two hemispheres operate differently supporting hemispheric lateralisation
how do adaptive advantages support hemispheric lateralisation
split brain patients performed better on some tasks, eg identifying odd one out in a group of objects, as the LH has better cognitive abilities in split brain patience and isn’t interfered with by the RH, supported by how lateralised chickens could find food whilst watching for predators but normal chickens couldn’t. this supports hemispheric lateralisation as the hemispheres are shown to be advantageous when separate
how does sperrys work support hemispheric lateralisation
highly scientific/standardised work, as all patients had a ‘fixation point’ and the image flashed for a 10th of a second, meaning sperry could ensure the image was received by one hemisphere rather than both, producing high internal validity making the study (a key foundation to hemispheric lateralisation) more reliable with its data
