Rapid extragranular plasticity in the absence of thalamocortical plasticity in the developing primary visual cortex

Monocular deprivation during early postnatal development remodels the circu itry of the primary visual cortex so that most neurons respond poorly to st imuli presented to the deprived eye. This rapid physiological change is ult imately accompanied by a matching anatomical loss of input from the deprive d eye. This remodeling is thought to be initiated at the thalamocortical sy napse. Ocular dominance plasticity after brief (24 hours) monocular depriva tion was analyzed by intrinsic signal optical imaging and by targeted extra cellular unit recordings. Deprived-eye responsiveness was lost in the extra granular Layers, whereas normal binocularity in layer IV was preserved. Thi s finding supports the hypothesis that thalamocortical organization is guid ed by earlier changes at higher stages.