biopsychology- hemispheric lateralisation Flashcards
hemispheric lateralisation
2 hemispheres of the brain are functionally different and that certain mental processes and behaviours are mainly controlled by one hemisphere rather than the other i.e. language
localisation of function
is the identification of function in a specific region of the brain e.g. the production of speech is localised to Broca’s area
lateralisation of function
the identification of a function in one hemisphere e.g. the right hemisphere specialised in visual-spatial processing and facial recognition
Which hemisphere processes the left visual field?
right hemisphere
Which hemisphere processes the right visual field?
left hemipshere
Where does the left visual field project to on the retina?
the nasal retina
where does the information sent to the contralateral hemisphere occur?
at the optic chasm
Which part of the retina does not send information to the contralateral hemisphere, and where is it sent?
Information from the temporal retina does not cross to the contralateral hemisphere, and instead sent to the ipsilateral hemisphere (same side)
At which point is the visual information combined, and which structure is involved?
Once the information reaches the cortex, it is shared across hemispheres via the corpus callosum
Where does the right visual field project information to?
the nasal retina of the right eye and the temporal retina of the left eye
What happens to visual information if the corpus callosum is severed?
Each hemsiphere will only have information from the contralateral visual field (from the temporal retina)
Which hemisphere is language largely processed in?
left
Which hemisphere are faces and facial emotion processed in?
right
Who conducted experiments on split-brain patients?
Sperry
What do we mean by ‘split-brain’ patients?
Surgery for intractable epilepsy involved severing the corpus callosum to prevent the spread of electrical discharge
What was Sperry’s experiment?
-used a divided field task, p’s look at dot located centrally on the screen. then visual info presented to left or right visual field for 0.1 seconds
-underneath screen was a table, p’s could feel but not see objects
Why was the visual stimulus presented so briefly?
so p’s couldn’t orient their head to stimulus which would cause both hemispheres to receive info
What happened when visual information was presented to the right visual field and why?
-subjects correctly recall the info as language processed in the contralateral left visual hemisphere
What would happen when visual information was presented to the left visual field, and why?
-p’s would nit report being any in of as as contralateral right hemisphere doesn’t have access to verbal info w/o input of left hemisphere
What happened when participants were asked to recognise objects presented to the left visual field by touch?
able to identify by touch with left hand as right hemisphere could process spatial info
What happened when composite faces (composed of a female and a male face), and why?
-p would say ‘man’ but left hand select the woman
-left hemisphere had superior verbal description
-right superior matching a face to a picture.
What do we conclude from work on split-brain patients?
-left hemisphere responsible for speech and language
-right hemisphere specialises in visual-spatial processing and facial recognition
-connectivity between regions is as important the operation of different parts
ao3- superior processing in some split brain patients
E- luck et al. (1989) split brain p’s twice as fast at identifying odd one out in array of similar objects. Kim peek could read 2 pages in around 10 seconds, had perfect recall of 12,000 books. likely developed bilateral language centres
E- Kingstone et al. (1995) suggests the LH’s superior processing abilities are ‘watered down’ by the inferior right hemisphere
L- supports Perry’s findings of ‘left brain’ and ‘right brain’ distinct in functions and abilities
ao3 hemispheric lateralisation- methodological issues, population validity
-sample 11 p’s
-may not be large enough sample to generalise
-may be inappropriate to make generalisations ab non-epileptic brain patterns from these p’s
-epileptic seizures could have made changes to the brain that could have affected the findings. confounding variable.
ao3 hemispheric lateralisation- contradictory evidence
-Gazzaniga (1998) suggests some early discoveries of research have been disconfirmed by more recent ones
-patient JW developed capacity to speak out of right hemisphere. so could speak ab info presented to the right brain
-indicates brains ability to adapt and shows language may not be exclusively limited to left hemisphere
-may not be as simplified as Sperry indicated and challenges validity of research
