Effects of Electroshock Convulsions on Chronic Decorticated Cats

Publisher Website
Google Scholar
Abstract
The effects of single and repeated electroshock convulsions were studied in 6 long-surviving chronic decorticated cats which were prepd. by removal of all neocortex together with portions of the caudate, thalamus, and pyriform lobes. Seizures were induced by passage of 200-450 milliamperes of 60 cycle A.C. from vertex to palate for 0.2-0.3 sec. Initially a posture of general semi-flexion was assumed and the extremities and mouth exhibited very rapid small amplitude rhythmic movements interrupted one or more times by brief periods of quiescence, finally terminating in running movements of the hindlimbs. Righting reactions returned within a few minutes. Licking reflexes were abolished for from 1/2-3 1/2 hrs. Sham rage responses to handling were unaffected or even intensified while sham rage responses to nociceptive stimulation (pressure on tail) were markedly reduced for from 1-2 1/2 hrs. No cumulative or new effects were seen after 5 to 9 daily electroshock convulsions. In terminal expts. the prepns. were curarized and maintained on artificial respiration. Electroencephalographic tracings before and immediately after passage of convulsing electroshock currents were made from screw leads in the vertex and the body of the sphenoid bone, using an ear as a reference electrode. Such tracing were characterized by bursts of relatively high voltage 2 to 21 cycles per sec. rhythms separated by short silent intervals, terminating in 15-18 cycles per sec. discharge. Slow and fast wave sequences appeared at times during such paroxysms and were more prominent in previously morphinized preparations. Neuropathologic examinations showed no changes in the remaining brains which could be attributed to the currents used. It is concluded that changes in adaptive behavior described by Masserman and Jacques (Amer. Jour. Psychiat. 104 92. 1947) following electroshock convulsions in intact neurotic cats are due to changes involving the cerebral cortex. The similarity of the motor and electroencephalographic patterns of the electroshock convulsions in chronic decorticated cats to those in the intact animal suggests that the seizures so induced in the latter are not dependent on the integrity of the neocortex.