ELECTROCORTICOGRAMS FOWLLOWING THRESHOLD TRANSCRANIAL ELECTROSHOCK FOR RETROGRADE AMNESIA IN CHICKS

Bipolar electrocorticograms were recorded both before and after transcranial electroshocks in 60 unanesthetized day-old chicks. Three shock intensities, 5, 10, or 15 ma, all 60 Hz and 0.45 sec in duration, were randomly assigned to different chicks. Only 15 ma caused motor convulsions, but both 10 and 15 ma had previously been found to have a definite retrograde amnesic effect that was absent at 5 ma. Analysis of the electrocorticograms was performed without knowledge of either the current intensity used or the behavioral response elicited. Spike activities were clearly present immediately after stimulation at both 10 and 15, but never at 5 ma. Subsequent flattening of the tracing occurred in different degrees only at 15, but never at 5 or 10 ma. The results show that the 10-ma stimulation was subconvulsive only with respect to overt motor responses. Association between EEG spike activities and amnesic effect was demonstrated. On the other hand, flattening of the EEG was shown to be unnecessary for retrograde amnesia. © 1969.