Paul Corballis

Department of Psychology, Dartmouth College, Hanover, NH, USA

Spatial Vision and the Right-Hemisphere Interpreter

The hemispheric organization of the human brain is one of its most obvious features. There is now a wealth of evidence for functional hemispheric asymmetries in several domains. Popular notions of hemispheric asymmetry hold that the left hemisphere tends to be specialized for processing verbal information, while the right hemisphere is specialized for visuospatial function. Callosotomy (or "split-brain") patients afford a unique opportunity to study the function of each cerebral hemisphere in isolation. These are patients who have undergone surgical section of the corpus callosum for the relief of epilepsy. Although more than three decades of research with callosotomy patients have revealed dramatic differences between the two hemispheres, they have also revealed that the prevailing beliefs about these asymmetries are simplistic and misleading. The most dramatic hemispheric differences observed in split-brain patients have been found in tasks tapping relatively high-level cognitive functions such as language and syllogistic reasoning. These findings have led Gazzaniga and his colleagues to postulate the existence of a left-lateralized cognitive module called the "interpreter" that performs these functions and attempts to resolve ambiguous events as they occur in the world. Evidence for right-hemisphere specialization has been more ephemeral. Some visuospatial functions seem to be performed equivalently by both hemispheres, whereas others appear to be strongly right lateralized. I will discuss some of these results, and suggest that the right hemisphere also performs "interpretive" functions that are geared towards resolving spatial ambiguity.

This page was last updated on 16 Feb 2001.

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