Abstract
In a series of studies it was shown that convulsions induced by metrazol and other convulsant agents or by electroshock as well as insulin hypoglycemia are accompanied by an increased excitability of autonomic centers at the hypothalamic and medullary level. 1 It was thought that this action is of greatest importance for the shock therapy of psychoses and may explain the fact that these procedures have similar therapeutic effects although their action on the cortex as measured by the electroencephalogram is quite dissimilar. 2
It seemed probable that hypoglycemic coma and convulsions may have in addition to their temporary influence on the cortex as revealed by the electroencephalogram far reaching effects on cortical processes which would be detected best by chronic experiments. Therefore the effects of these procedures on the conditioning process were studied.
The experiments were performed on 17 rats which received as an unconditioned stimulus a shock inducing them to jump from a compartment A across a small partition into the compartment B. This reaction was established by a few shocks. Thereafter a bell was sounded 2 seconds prior to shock. The sound continued during the shock. After the conditioned response (C.R.) was established at nearly 100% for 1 to 3 days the C.R. was inhibited by lack of reinforcement. When the C.R. response had either completely disappeared or was present only in 10-20% of the tests the rats were subjected either to metrazol convulsions, electroshock or insulin coma. Whereas control animals not subjected to these procedures showed no spontaneous recovery of the C.R. it was observed that the experimental group treated with coma or convulsions regained the inhibited C.R. in spite of continued lack of reinforcement. The duration of this effect was variable and depended on the number of “treatments” and in the case of insulin probably on the depth and the duration of the coma.
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