Lateralisation and split-brain research Flashcards
What is hemispheric lateralisation?
The idea that the two halves/hemispheres of the brain are functionally different (have different specialities).
Outline three roles of the left hemisphere.
Language centre
Controls right side of body (e.g. right hand)
Receives info from right visual field
Outline three roles of the right hemisphere.
Focuses on visuo-spatial tasks
Controls left side of body (e.g. left hand)
Receives info from left visual field
If language is located in the left hemisphere, how can we talk about things that are experienced in the right hemisphere such as face recognition.
Hemispheres connected by corpus callosum. Allows info from one hemisphere to be sent to the other.
Who used split brain studies to investigate hemispheric lateralisation?
Sperry
Who were the participants in Sperry’s split-brain research?
All had severed corpus callosums and other tissues connecting hemispheres to control epileptic seizures.
Describe the procedure of Sperry’s split-brain research.
Image or word projected to either a patient’s left or right visual field. Patient then asked to make responses with their left hand, right hand or verbally (describe/draw what they saw).
How would one of Sperry’s patients verbally respond if an image of a dog was flashed into the right visual field? Why?
Would say they saw a dog. Right visual field - left hemisphere. Language centre in left hemisphere so connection can be made.
How would one of Sperry’s patients verbally respond if an image of a dog was flashed into the left visual field? Why?
Would say they saw nothing. Left visual field - right hemisphere. Right hemisphere can see picture, but has no language centre so cannot respond verbally.
How could one of Sperry’s patients identify an object presented in the left visual field? Why?
Select a matching object using their left hand. Left visual field - right hemisphere. Right hemisphere controls visuo-spatial tasks. Info does not need a corpus callosum to connect. (Cannot verbally describe it, but can still ‘understand’ what the object is using the right hemisphere).
What did we learn from split-brain research?
There are a number of clear differences between the hemispheres. They have independent functions. Suggests the importance of connectivity for normal functioning.
(AO3) What is a strength of the methodology used by Sperry?
Precise standardised procedure - presenting visual info to one hemispheric field at a time (clever mf). patients stared at fixed point with one eye, image flashed up for 0.1 sec. No time to move eyes over image to spread info to other visual fields. Well controlled, easy to manipulate and replicate so high in internal validity and reliability.
(AO3) Why is generalisation such an issue with Sperry’s research?
Small, unusual sample: 11 patients with history of seizures. May have caused unique changes to brain, influencing findings. Difficult to generalise to normal brains - reducing population validity.
(AO3) How does functional recovery reduce the credibility of hemispheric lateralisation?
Suggests other areas of the brain can compensate for damage to a specific region and carry out said function. ‘Independent functions’ may not be so clear-cut. Sperry’s research may have over-simplified findings.
(AO3) Name an advantage and a disadvantage of hemispheric lateralisation.
If each hemisphere can perform different tasks simultaneously, it may improve the efficiency of our brains (explains multi-tasking). But limited empirical evidence for this.
Mathematically gifted have superior right-hemispheres but also more likely to suffer immune system problems.
