Deafferentation of the visual cortex: the effect on cortical cells in normal and in early monocularly deprived cats.

The optic tract was unilaterally transected and receptive field mapping and unit recordings were made for cells in the boundary of areas 17-18 in the deafferented and in the intact visual cortex of adult cats monocularly deprived during the critical developmental period. Three groups of adult animals served as controls: normal cats, early monocularly deprived (MD) cats, and optic tract transected cats. In contrast to the activity found in the intact hemisphere, the deafferented hemisphere of the experimental group was almost completely unresponsive. The ocular dominance distribution in the intact hemisphere of the experimental group (75.0% cells monocularly driven by the normal eye) was similar to that of the control MD cats (78.1%). This indicates that cutting the optic tract after the critical period does not affect the ocular dominance distribution of cortical cells induced in the intact hemisphere by early monocular deprivation. The reduction found in the proportion of visually responsive cells and the orientation and direction selective cells in the intact hemisphere of the experimental group, is mainly due to the isolation of the fellow hemisphere from its direct visual input, and the subsequent inactivation of the callosal pathway interconnecting the two visual areas.