The unilateral engram

It is proposed that the corpus callosum has a major role in the processes of memory; first, by providing access by each hemisphere to memory traces stored in the other, and second, by controlling the formation of memory traces in such a way that they are laid down in only one hemisphere instead of in both. This dual mechanism would have the effect of doubling the mnemonic storage capacity of the brain. Evidence in favor of this hypothesis in briefly reviewed. It is also supported by experiments using electrical excitation of the striate cortex as a conditional stimulus in macaques, and by experiments on maze behavior in the m e species. Experiments with the anterior commissure, on the other hand, show that it, in contrast to the splenium of the corpus callosum, can actually transfer an engram from one hemisphere to the other. Finally, it is shown that the splenium provides an effective path of communication between the central visual system in one hemisphere and the amygdala in the other.