Disconnected cerebral hemispheres after callosotomy: A disconnected mind?

The term ‘split-brain’ patient (or simply, split-brain) typically refers to a patient whose brain has been surgically treated in order to resect one or more major commissures interconnecting homologous cortical regions of the two cerebral hemispheres. The aim of the present thesis is to describe the reasons this surgery is carried out and, more importantly, the cognitive consequences of isolating the two cortical hemispheres in an adult brain. Starting with the description of the neurological disease termed epilepsy, the focus is set on a particular surgery, known as commissurotomy, which is performed as treatment for epilepsy that are resistant to pharmacological treatment. The description of the surgery, that consists in the resection of part of the corpus callosum, lead to an overview of the structures that surrounds the corpus callosum and of the anatomy of this part of the adult brain. Then the consequences of this surgery are addressed, and the iatrogenic symptoms are described and explained, outlining a new functional view to the brain anatomy. Considering the impact of the surgery from a psychological perspective, the possibility of existence of two separate consciousness is addressed. One of the main discussions is on “how the brain can recover some lost functionalities” that lead to three great hypotheses taking in account: strengthening of subcortical connections, internal cueing, and external cueing. The thesis concludes illustrating critically a subset of answers that populated the literature in the recent past.