Split-brain

“Split-brain” or callosal syndrome is a disconnection syndrome that arises when the corpus callosum connecting the two cerebral hemispheres is severed, typically via a surgical corpus callosotomy to treat refractory epilepsy.

Behavioral and Cognitive Effects

After the procedure, each hemisphere develops its own separate perception, concepts, and impulses.

• Lateralized Processing: A split-brain patient shown an image only in their left visual field (processed by the right hemisphere) cannot verbally name what they see because the speech-control center is typically in the left hemisphere, and the interhemispheric transfer is severed.
• Intermanual Conflict: In some cases, the patient’s two hands may act in opposition (e.g., one hand pulling pants up while the other pulls them down), demonstrating conflicting impulses from the isolated hemispheres.

History and Research

Roger Sperry and Michael Gazzaniga pioneered split-brain research in the 1960s. Their studies revealed that the left hemisphere is more analytic and specialized for language and logic, whereas the right hemisphere is holistic and specialized for spatial tasks, facial recognition, and emotion. The profound implication of a “divided consciousness” has made split-brain patients a focal point in the philosophy of mind and studies on the unity of the self.