Split brain: divided perception but undivided consciousness

Yair Pinto led this from the Department of Psychology and the Amsterdam Brain and Cognition Center at the University of Amsterdam, a consciousness researcher in the recurrent-processing tradition of his co-author Victor Lamme. The co-authors span Amsterdam, the Donders Institute, Auckland, and the Ancona epilepsy and anatomy groups (Nicoletta Foschi and Mara Fabri, who provided the two callosotomy patients tested). The paper is a deliberate, named challenge to the textbook reading of the split brain.

It appeared in 2017 in Brain, the same senior peer-reviewed neurology journal that carried Gazzaniga's 2000 review, which gives the revision its standing. The study tests two fully callosotomised patients across many tasks and replicates the classic result that stimuli cannot be compared across the two visual half-fields — perception is genuinely split. What it does not replicate is the canonical claim that each hemisphere can only respond to its own half of space with its own hand: the patients reported the presence, location, orientation, and identity of stimuli anywhere in the field, with either hand or by speaking.

This sits as a primary, revisionist report. From the divided perception and the undivided responding, the authors argue for one conscious agent rather than Sperry's two, which reopens the unity-of-consciousness question and poses a problem for Global Workspace and Integrated Information theories that tie consciousness to information integration. The classic defence of the two-hemispheres reading runs through cross-cueing — that the patients leak information through the body — which Pinto and colleagues argue is too low-bandwidth to account for what they saw.

The authors' stake is theoretical and reputational. The paper is openly set against the Sperry–Gazzaniga interpretation and is positioned within a specific camp in consciousness science, so it carries an agenda — which it states rather than hides — and its strength rests on two patients, a base the authors are candid about.