Collaboration between the hemispheres of a callosotomy patient - Emerging right hemisphere speech and the left hemisphere interpreter

Split brain patients who are initially unable to produce speech in their right hemispheres sometimes develop the ability to do so. Patient J.W., the subject of this report, is such a patient At the time of his callosotomy, J.W. had a language dominant left hemisphere; his right hemisphere could understand both spoken and written language but he was unable to speak. Fourteen years after his surgery, we found that J.W. was capable of naming similar to 25% of the stimuli presented to his left visual field (LVF). Now, 1 year later we find that he can name about 60% of such stimuli. This late-developing speech ability appears to be the consequence of long-term neural plasticity. However the subject's extended verbal responses to LVF stimuli seem to result from a collaboration between the hemispheres and to involve the left hemisphere interpreter.