Some Studies of Interhemispheric Integration in the Rat

Abstract

The most central problem of the study of the commissures and hemispheric integration is the question of whether or not a single or a duplex record of experience is established in the brain. In other words when an animal is trained on a visual problem with binocular vision, is the information stored as two separate and independent records in the two hemispheres, or as a single record across both hemispheres? The interest in the question derives from the early work of Sperry (1961) which established the essential point that monocular visual training in the cat with both chiasm and commissures sectioned resulted in memory lateralisation to one hemisphere. By contrast, monocular training in either the chiasm-sectioned or the callosum-sectioned animal did not produce memory lateralisation. These findings were interpreted to imply that in the normal intact brain the visual information is integrated during binocular vision by both the chiasm and the commissural system to result in two separate records, one in each cerebral hemisphere. This is what is known as the bureaucratic theory of the brain, where everything is stored in duplicate form at least at a cortical level. If we consider the colliculi, it may even be necessary to think in terms of quadruplicate storage.