Hemispheric Specialization and Interaction

Hemispheric Specialization
In Verbal and Spatial issue, the evidence of hemispheric specialization comes from Gazzaniga, 1979, who studies split- brain patients. He found out that right- handed patients are capable of solving visuospacial tasks with their left hand (right hemisphere), but not with their right hand (left hemisphere), and the opposite occurs with verbal tasks. Hence, this study provided strong evidence for right hemisphere spatial specialization, and left hemisphere for language process.
There is still another hemispheric specialization called production and monitoring. This model was tasted by comparing PFC activity during recall and recognition tasks (Cabeza, Locantore, & Anderson, 2003). The recall task here is a kind of semantically guided production processes mediated by the left PFC，and this production processes are more critical for recall than recognition; Whereas monitoring processes mediated by the right PFC are responsible for evaluating external and internal information, which are what recognition tasks asked to do.
Hemispheric Interaction
When it comes to how hemispheres interact to each other, three models are applied：insulation, inhibition and cooperation. The evidence of hemispheric insulation comes from Cherbuin and Brinkman, 2005. They claimed that” the division of relevant inputs in the across visual field hemispheric interaction condition appears to decrease the interference caused by changing hemispheric activation patterns, which is consistent with past finding related to dual task interference(Merola & Liederman.1990)”. As to the inhibition view, M ller-Oehring et al.（2007）found that “corpus callosum mediates lateralized local-global processes by inhibition of task-irrelevant information under selective attention conditions”. At the last, cooperation model, Patel and Hellige(2006) concluded that” By collaborating with each other, the two hemispheres together can provide more computational power than either hemisphere can provide by itself”. However, I rather believe that there isn’t such clear distinction between three models, because hemispheric interaction would be affected by task load, domain hemisphere, gender and attention allocation et al.. And we can't use only one model explaining the hemispheric interaction in all kinds of tasks and conditions. Thus, although there are evidences to support three models, especially bilateral advantage, we can’t conclude any one of them is the absolute model. Instead, we can say that when two hemispheres act simultaneously, corpus callosum would change it’s function depends on tasks and conditions.