Regional characteristics of electrical responses (in the band 1-225 Hz) in the cerebral cortex to conditioned stimuli in operant conditioning.

Power spectra of short-term (less than 1 sec) electrical responses to conditioned stimuli were studied over the frequency range 1-225 Hz in dogs during food-related operant conditioning. These spectra demonstrated regional characteristics in terms of energy levels and frequency composition. Responses were more marked in the visual and parietal areas of the left hemisphere. Power in responses to a differential stimulus were significantly lower than with responses to positive stimuli, mainly because of the high-frequency range (80-225 Hz); energy levels in these two situations were similar during prestimulus intervals. The frequency composition of responses was defined by a series of discrete frequencies in the gamma (30-80 Hz) and high-frequency ranges.