Single whisker experience started on postnatal days 0, 5 or 8 changes temporal characteristics of response integration in layers IV and V of rat barrel cortex neurons

Neonatal single whisker experience changes the response properties of spared barrel neurons to deflections of principal and adjacent whiskers. However little is known about the temporal characteristics of the paired whisker inputs. To address this issue we used computer controlled mechanical displacement of paired whiskers in control and plucked animals (plucking of all whiskers but D2 started at 0, 5 and 8 postnatal days). The principal whisker (PW) and its caudal adjacent whisker (AW) were deflected simultaneously or serially at different inter-stimulus intervals (10, 20, 30, 50 and 100 ms). Neuronal responses were recorded in D2 spared barrel both in layers IV and V. In the control group, combined deflection of AW prior to PW led to suppression of ON and OFF responses to PW deflection both in layers IV and V. The magnitude of this suppression was strongly dependent on the inter-stimulus intervals (ISIs). At almost all tested ISIs, whisker plucking from P0, P5 and P8 weakened suppressive interactions in layers IV and V barrel neurons for both ON and OFF responses. The most decrease in inhibitory interactions was observed in P5 plucked animals. Principal whisker-evoked ON responses were increased only in P0 plucked animals both in layers IV and V. AW-evoked ON responses are decreased in P5 plucked animals in layer IV. The available data suggest that sensory experience can modulate temporal aspects of response integration and receptive field properties of layers IV and V neurons in barrel cortex. These changes have different critical periods.