Identification of principal components in cortical evoked potentials by brief surface cooling

Objectives: The evoked potential recorded by a single electrode in rat's ba rrel cortex after whisker stimulation was shown to be composed of two main principal components shifted in time by about 3 ms. The purpose of this stu dy was to verify the hypothesis that these components represent activity of supra- and infragranular pyramidal cell classes.\ Results: Our results show that a brief cooling pulse applied to the cortica l surface abolishes the shorter latency component, which may therefore be a ttributed to the response of supragranular pyramidal cells. Conclusions: The longer latency principal component, which disappears only with strong cooling pulses, is proposed to represent postsynaptic activity of infragranular pyramidal neurons. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.