The role of activity in corpus callosum development in the visual cortex

Many previous models have explained how ocular dominance- and orientation selective columns could develop in the visual cortex. However, few models have investigated the topographic arrangement of interhemispheric connections between primary visual areas. A new model of the development of corpus callosum connections in cat visual cortex was recently introduced (Hely, 1999). The model showed how the observed hour-glass pattern of callosal receptive field (RF) positions arises as a consequence of the retinotopic mapping onto the cortex. In the cat, callosal connections only form between cells with visual field RFs located close to the vertical meridian. In contrast in rat visual cortex, callosal connections also form between cells with RFs in the peripheral visual field. This cannot be accounted for using a Hebbian rule based on spatial information alone. The current generic model of primary visual cortex was extended by including optic-flow/motion information. This extra input enabled cells with peripheral RFs fields in the medial cortex to make connections to the opposite hemisphere. The results from the model suggest that in some species motion information may affect the development of connections in primary visual cortex.