Impairment of binocular vision in the adult cat induces plastic changes inthe callosal cortical map

In the primary visual cortex of normally reared adult cat, neurons activate d through the corpus callosum are almost entirely located at the 17/18 bord er. They display small receptive fields distributed along the central verti cal meridian of the visual field and are orientation selective. Here we dem onstrate that a few weeks of monocular deprivation or unilateral convergent strabismus produced in adulthood does not modify the cortical distribution of these neurons, but leads to an increase of their receptive field size m ainly toward the ipsilateral hemifield and to a loss of their orientation s electivity. We conclude that manipulation of binocular vision in the adult modifies neither the location of the primary callosal cortical map nor its retinotopy. In contrast, it induces functional plastic changes in this map which lead to a significant widening of the area of visual space signalled through the corpus callosum. These plastic changes are interpreted as the r esult of the strengthening of normally hidden subthreshold synaptic inputs.