Effect of atropine on intracortical evoked potentials during classical aversive conditioning in cats

In this article, intracortical evoked potentials (EPs) were recorded simultaneously from six different depths of the auditory cortex of freely moving cats. The effect of (a) different states of vigilance and that of atropine, (b) classical aversive conditioning, and (c) the effect of atropine during conditioning was studied on the intracortical EP profiles. Atropine induced EP changes that were similar to those seen in slow wave sleep. During classical aversive conditioning signal stimuli elicited a middle-latency negative EP component which was localized to the superficial cortical layers. Atropine (2 mg/kg body weight) did not abolish the appearance of this component but only increased its latency. It is proposed that the cholinergic part of the ascending activating system did not play an essential role in its generation.