Defensive conditioning of electrographic arousal with delayed and differentiated auditory stimuli

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1. 1. In three cats, a delayed (2 min.) auditory conditioned stimulus associated with moderate shock to the skin, produced in the electrographic sleep record a characteristic pattern of: ( a) an initial brief activation followed by ( b) a more prolonged period of synchrony, changing usually midway through the CS to ( c) a return of activation enduring to the delivery of the unconditioned stimulus. Recording points leading in the development of activation and showing the greatest resistance to synchrony were auditory cortex, reticular formation, and hippocampus. Points showing the reciprocal predominance of synchrony and resistance to activation were in association cortex. 2. 2. The degree and duration of synchrony present during the first half of the CS varied inversely with the intensity of the US and directly with the progression of trials in a given daily session. Synchrony was not definitely present until the conditioned stimulus had been extended longer than one minute. 3. 3. A differentiated stimulus of 20 sec. duration, applied after full differentiation in combination with the CS during the early synchrony response, briefly desynchronized that response, without disturbing the total duration of synchrony or the overall conditioned electrographic response pattern. 4. 4. When combined with the CS and associated to a withholding of reinforcement, the differentiated stimulus evoked marked synchrony during the standardized activation response to the second half of the delayed conditioned stimulus. 5. 5. Interpretations of these findings in relation to Pavlovian inhibition, hypnogenic inhibition theory of sleep, and competitive interactions in the brain are discussed.