Electrophysiological and morphological correlates in the development of visual cortical circuitry in infant kittens.

Geniculate axons in cat visual cortex establish excitatory connections with cortical cells in supragranular and granular layers at birth. They are localized to the granular layer for the first month after birth. Retraction of geniculocortical synapses parallels axonal extension of spiny stellate cells to the supragranular layer and establishment of synapses for intracortical transmission.