Cortical map asymmetries in the context of transcallosal excitatory influences

There is long-standing disagreement among experimentalists about whether tr anscallosal interhemispheric influences are primarily excitatory or inhibit ory. Past computational models exploring this issue have encountered a simi lar dilemma: inhibitory callosal influences best explain hemispheric functi onal asymmetries, but excitatory callosal influences best explain transcall osal diaschisis. We recently hypothesized that this dilemma might be resolv ed by assuming excitatory callosal influences and a subcortical mechanism f or cross-midline inhibition. Here we explore the feasibility of this hypoth esis by examining a model of map formation in corresponding left and right cortical regions. The results show for the first time that both map asymmet ries and diaschisis-like changes can be produced in a single model, suggest ing that subcortical inhibitory processes may contribute more to asymmetric cortical functionality than is generally recognized. NeuroReport 12:1609-1 614 (C) 2001 Lippincott Williams & Wilkins.