hemispheric lateralisation Flashcards
what is hemispheric lateralisation?
the idea that two hemispheres are functionally different
certain mental processes and behaviours are mainly controlled by on hemisphere rather than the other,
e.g. language
what is the difference between localisation and lateralisation?
localisation = identification of function in a specific region of the brain.
whereas lateralisation is the identification of a function in one hemisphere.
which hemisphere processes the left visual field?
right hemisphere
which hemisphere processed the right visual field?
left hemisphere
where does the left visual field project to on the retina?
to the nasal retina of the left eye and the temporal retina of the right eye
which part of the retina sends info to the contralateral hemisphere?
were does it occur
the nasal retina
it occurs at the optic chiasm
which part of the retina does NOT send information to the contralateral hemisphere and where is it actually sent?
info from the temporal retina does not cross to the contralateral hemisphere, and is instead sent to the ipsilateral hemisphere.
at which point is the visual information combined, and which structure is involved?
one the info reaches the cortex, it is shared across hemispheres via the corpus callous
where does the right visual field project information to?
to the nasal retina of the right eye and to the temporal retina of the left eye.
what happens to visual info if the corpus callous is severed?
each hemisphere will only have info from the contralateral visual field.
which hemisphere is language largely processed in?
left
which hemispheres are faces and facial emotion processed in
right
who conducted experiments for split brain patients?
Roger sperry
what do we mean b split brain patients?
Surgery for intractable epilepsy involved severing the corpus callosum to prevent the spread of electrical discharge
– this is known as a commissurotomy, preventing communication between the hemispheres.
what was sperrys experiment?
He used a divided field task, in which patients would look ahead a dot located centrally on the screen, and then visual information would be presented to the left or right visual field for 0.1 seconds.
Underneath the screen was a table, in which participants could feel, but not see objects.
why was the visual stimulus presented so briefly?
So that participants could not orient their head to the stimulus, which would then mean both hemispheres would receive the information.
What happened when visual information was presented to the right visual field and why?
Subjects would correctly recall the information because language is processed in the contralateral left visual hemisphere.
What would happen when visual information was presented to the left visual field, and why?
Patients would report not seeing any information, because the stimulus was processed by the contralateral right hemisphere, which does not have access to verbal information, without the input of the left hemisphere.
What do we conclude from work on split-brain patients?
- the left hemisphere is responsible for speech and language and the right hemisphere specializes in visual-spatial processing and facial recognition.
- It not shown that the brain is organised into discrete regions with specific sections responsible for specific task.
- it suggests that the connectivity between the different regions is as important as the operation of the different parts.
What happened when participants were asked to recognise objects presented to the left visual field by touch?
why?
Participants were able to identify the objects by touch with their left hand, because the right hemisphere was able to process spatial information.
What happened when composite faces (composed of a female and a male face), and why?
The ppt would say ‘man’ but the left hand would select the woman.
The left hemisphere had superior verbal description and the right superior matching a face to a picture.
