Artificially respirated rats with skeletal muscles completely paralyzed by curare were rewarded by electrical stimulation of the medial forebrain bundle for either increasing or decreasing their heart rates. After achieving the easy criterion of a small change, they were required to meet progressively more difficult criteria for reward. Different groups learned increases or decreases, respectively, of 20%; 21 of 23 rats showed highly reliable changes. The electrocardiogram indicated that decreased rates involved vagal inhibition. Rats learned to respond discriminatively to the stimuli signaling that cardiac changes would be rewarded.

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A total of 40 normal and 40 neodecorticate rats, paralyzed by d-tubocurarine, were used in two experiments. Different groups of rats received instrumental training and classical conditioning of either heart rate or intestinal activity. A control group consisted of rats receiving random presentations of the CS and US used in the classical conditioning experiment. The results indicated that the intact neocortex is necessary for the instrumental learning of cardiac and gastrointestinal responses, but that it is not necessary for the classical conditioning of these responses. No relationship could be discerned between the cortical lesions, which included over 90% of the neocortex, and the extent of cardiac or gastrointestinal change achieved by either classical or instrumental training paradigms.

2 groups of curarized rats learned to increase or decrease, respectively, their heart rates in order to escape or avoid mild electric shocks. Responses in the appropriate direction were greater during the stimulus preceding shock than during control intervals between shock; they changed in the opposite direction, toward the initial pretraining level, during the different stimulus preceding nonshock. Electromyograms indicated complete paralysis of the gastrocnemius muscle throughout training and for a period of at least 1 hr. thereafter.

No abstract