Abstract
Somatosensory cortical circuits are modified in an activity-dependent manner. Somatosensory information is serially processed by the primary (S1) and secondary (S2) cortices. In the present study, we investigated activity-dependent modification of the functional connections between S1 and S2 in rat cortical slices. Neural activities were elicited by repetitive electrical stimulation, and visualized using green autofluorescence of flavoproteins in blue light. The stimulation applied in S1 produced neural responses spread into S2. However, when S2 was stimulated, the neural activities were not invaded into S1. We also investigated the properties of the functional connections with field potential recordings and patch clamp recordings from pyramidal neurons. The anisotropic propagation of neural activities demonstrated using autofluorescence imaging was confirmed by the electrophysiological experiments. Activity-dependent changes in neural activities were observed in the barrel cortex one or two weeks after trimming the contralateral whiskers. In these slices, supragranular neural activities after stimulation of infragranular layers were clearly suppressed. Furthermore, neural activities elicited by S1 area near the border between S1 and S2 were spread into the adjacent barrel cortex area rather than into S2. These results suggest the activity-dependent modification of the barrel cortex circuits and functional connections between S1 and S2. [Jpn J Physiol 55 Suppl:S163 (2005)]
