Hemispheric integration is critical for intact error processing.

We provide for the first time direct clinical evidence for the critical role of hemispheric integration in intact error processing. We tested three patients with partial callosal disconnection. Two anterior patients could not correct their errors in a unilateral version of a visuomotor learning task for which they previously exhibited callosal disconnection, whereas, they corrected most of their errors in two visual matching tasks (comparing abstract shapes or faces) that they could transfer between the hemispheres. An opposite pattern emerged in a posterior patient. He could not correct his errors in unilateral versions of the same visual matching tasks, for which he previously exhibited callosal disconnection. However, he corrected most of his errors in the visuomotor learning task he was able to transfer between the hemispheres.