Neuronal mechanisms of developmental plasticity in the cat's visual system.

During early postnatal development various response properties of single neurones can be changed in the cat's visual system. These modifications must be based on changes of synaptic efficacy and depend on neuronal activity. Rearing kittens with artificial astigmatism creates meridional amblyopia demonstrable on different levels of investigation. Characteristic interdependencies of ocular dominance and orientation preference in visual cortex can be generated that demonstrate that synaptic changes involve a postsynaptic gating mechanism. The same conclusion can be drawn from the results of monocular strobe rearing, which has differential effects on cells in different cortical laminae. Connectivity changes can be induced by rather brief stimulation, but need time for consolidation, as can be shown by reverse occlusion experiments. Deprivation effects may also act across sensory modality borders: auditory neurones in superior colliculus are found much more frequently after visual deprivation. Judging from the number of bimodal cells, synaptic competition may be less powerful here than in visual cortex.