Abstract

Central electrical responses to a flickering light (TCS) have been recorded from cats having electrodes chronically implanted in cortical and subcortical areas during a) initial presentation of the stimulus, b) familiarization, c) acquisition and performance of a conditioned avoidance response (CAR), d) generalization to other frequencies of flickering light, e) transfer to pulsed auditory stimulation, f) blockade of the CAR by reserpine and g) extinction of the CAR.

Frequency-specific responses (labeled responses) recorded from visual cortex, auditory cortex, lateral geniculate, superior colliculus, amygdala and hippocampus upon first presentation of the TCS waned and disappeared during the familiarization process.

With the initial pairing of shock with TCS, labeled responses reappeared in all structures except the amygdala and hippocampus. The responses were modified in form and amplitude in the different areas of the brain in different phases of learning. Of particular interest was the shift in location of labeled responses from the classical visual pathway to the extralemniscal ascending system and then back to the major visual path again during successive stages of avoidance training.

At 100% CAR 40/sec burst activity in the amygdala and multiples of the TCS frequency in the cortical responses were characteristic features.

Evidence of the functional relevance of the electrical responses observed in certain central structures was obtained by studies of generalization, of transfer and of the effects of reserpine.