A critical period for long-term potentiation in the developing rat visual cortex.

The in vitro rodent visual cortical slice preparation demonstrates a critical period for long-term potentiation (LTP). Current source density (CSD) analysis reveals peak potentiation of both supra-(layers II-III) and infragranular (layers V) layers of visual cortex during the second postnatal week following stimulation of the subadjacent white matter. By day 30 both the supra- and infragranular CSD sinks show only minimal potentiation. In adults there is no change in supragranular response but infragranular layers reveal 177% potentiation. Therefore, we conclude that rodent visual cortex displays a critical period for maximum plasticity of both supra and infra-granular layers. Supragranular visual cortex plasticity ends by day 30 whereas infragranular layers retain plastic qualities into adulthood.