The Split brain

1. Terminology The term split-brain has several meanings. Applied to the human, it denotes complete sectioning of the corpus callosum, an operation which is usually performed for medically intractable, multifocal epilepsy (Reeves and Roberts, 1995). In the experimental animal, such as the cat or monkey, it usually implies both callosal section and a split optic chiasm; this makes it possible to restrict visual information to one hemisphere merely by covering one eye. In the human with intact chiasm, restriction of visual input to one hemisphere requires restriction of the visual stimuli to one or the other visual hemifield. Our split-brain patients had complete cerebral commissurotomy (including anterior commissure, dorsal and ventral hippocampal commissures, and, in some cases, the massa intermedia). But it is now common to use the term split-brain to refer to cases of complete callosotomy alone, since they manifest most of the same signs and symptoms.