LAMINAR COMPARISON OF SOMATOSENSORY CORTICAL PLASTICITY

During tactile learning there is a transformation in the way the prima ry somatosensory cortex integrates, represents, and distributes inform ation from the skin. To define this transformation, the site of earlie st modification has been identified in rat somatosensory cortex after a change in sensory experience. Afferent activity was manipulated by c lipping all except two whiskers on one side of the snout (''whisker pa iring''), and the receptive fields of neurons at different cortical de pths were mapped 24 hours later. Neurons in layer IV, the target of th e primary thalamic pathway, were unaltered, whereas neurons located ab ove and below layer IV showed significant changes. These changes were similar to those that occur in layer IV after longer periods of whiske r pairing. The findings support the hypothesis that the layers of cort ex contribute differently to plasticity. Neurons in the supragranular and infragranular layers respond rapidly to changes in sensory experie nce and may contribute to subsequent modification in layer IV.