INTERHEMISPHERIC-TRANSFER AND AGENESIS OF THE CORPUS-CALLOSUM - CAPACITIES AND LIMITATIONS OF THE ANTERIOR COMMISSURE

In case of agenesis of the corpus callosum, four hypotheses may be pro posed to explain how compensation of the interhemispheric transfer mig ht take place. These hypotheses include the use of cross-cueing behavi oral strategies, the bilateral representation of speech-functions, the increased use of ipsilateral sensory-motor pathways, and the use of n oncallosal commissures. Among all these compensatory mechanisms, the l ast one, namely the increased use of the anterior commissure, is the m ost significant. It can easily explain that acallosal patients with an anterior commissure (which can be increased in size), have better res ults in interhemispheric transfer tests, and in neuropsychologic tests , than patients having no anterior commissure. However, the anterior c ommissure alone, even increased in size, cannot normalize all the inte rhemispheric transfer tests. because of the big difference between the field of origin of the callosal fibers, and the field of origin of th e anterior commissure fibers.