Split-brain research

• Split-brain patients are individuals who have undergone a surgical procedure where the corpus callosum, which connects the two hemispheres, is cut. This procedure, which separates the two hemispheres, was used as a treatment for epilepsy. 
• The aim of research was to examine the extent to which the two hemispheres are specialised for certain functions. An image/word is projected to the LVF or the RVF. When information is presented to one hemisphere in a brain patient, the information is not transferred to the other (corpus callosum is cut).

  • Describing task

  Picture was shown to either LVF/RVF and participants described what they saw. 

  • Tactile test

  Picture was placed in LVF/RVF and had to say what they felt, or pick a similar object.

  • Drawing task

  Participants given a picture in LVF/RVF and drew what they saw. 
• One strength of split-brain research is it shows laterlised brain functions. 


  The left hemisphere is analytical and verbal (‘the analyser’) and the right is adept at spatial tasks and music (‘the synthesizer’). The right hemisphere can only produce basic words and phrases but contributes emotional content to language. Recent research suggests this distinction may be too simplified and several tasks associated with one hemisphere can also be carried out by the other. 
• Another strength is the methodology that Sperry used. 


  Sperry’s carefully standardized procedure of presenting visual information to one hemispheric field at a time was quite ingenious. Participants stared at a fixed point with one eye. An image was flashed up for 0.1 seconds, so the patient had no time to move their eyes over the image and spread the information across both sides of the visual field or both sides of the brain. This allowed Sperry to vary aspects of the basic procedure and ensure only one hemisphere received information at a time - a very useful and well-controlled procedure.
• One limitation is issues with generalization in relation to Sperry’s work.


  Many researchers have said these findings cannot be widely accepted, as split-brain patients are such an unusual sample of people. Only 11 patients took part in all variations and all had a history of seizures. This may have caused unique changes in the brain that influenced the findings. This limited the extent to which the findings can be generalized to normal brains, reducing the validity of the conclusions. 
• A further limitation is differences in hemispheric functions may be overstated. 

  A legacy of Sperry’s work is a growing body of pop-psychological literature that oversimplifies and overstates the difference in function between the two hemispheres. Modern neuroscientists argue these distinctions are not all clear-cut. Many behaviors that are typically associated with one hemisphere can be performed by the other when situations require. The apparent flexibility of the two hemispheres suggests some of the conclusions drawn by Sperry may be too simplistic.