Conditioned responses in the visual cortex of dogs. II. During sleep

Repetitive electrical stimulation of the optic chiasm was used as a cue stimulus for alimentary conditioned lever-press in dogs. During sleep after conditioning, the cue was presented to test whether the conditioned response (CR) can be emitted during sleep and whether CR in visual cortex (VC) is due to change in excitability in VC. Though level-press behavior never occurred without accompanying EEG arousal responses, rate of occurrence periods of EMG (percent EMG) and rate of EMG in the lever-press forelimb increased in the conditioned animals. Amplitudes of components 4 and 5 of the evoked potential in VC enhanced during both slow-wave (SS) and fast-wave sleep (FS) with similar time course as in wakefulness. In addition, correlation between latency of the EMG and of maximum enhancement of the amplitudes which was obtained during wakefulness remained during these sleep stages. Enhancement of the amplitudes was greater during sleep than during wakefulness; no significant difference was found between SS and FS. These results support the hypothesis that the CR in VC is attributed to excitability change and suggest that CR, in the peripheral and central level, can be emitted during SS and FS periods in dogs.