Effects of neonatal C-fiber depletion on discrimination of principal and adjacent whisker stimulation within rat individual cortical barrels.

Controlled mechanical displacement was used to stimulate single whiskers in normal and C-fiber depleted rats to quantitatively examine the role of C-fibers in the response properties of barrel cortical cells. C-fiber depletion using neonatal capsaicin treatment increased the barrel single-unit response magnitude to deflection of both principal and adjacent whiskers while there was not any significant difference in the barrel cells' spontaneous activity. Capsaicin treatment increased the neural response duration of adjacent whisker stimulation but did not change that to the principal whisker deflection. There was no difference in response latencies of principal or adjacent whisker displacement between the normal and C-fiber-depleted groups. The efficiency of neural code for differentiation of principal and adjacent whiskers was measured by ROC analysis, which reflects the performance of an ideal observer in this discrimination using cells' firing rate. No significant difference was found in the performance of neurons in capsaicin-treated and control groups in distinguishing principal and adjacent whisker deflections from each other. These results suggest that neonatal C-fiber depletion causes an expansion of barrel cells receptive field but it does not affect the discrimination of individual whisker stimulation by the barrel cells.