Constancy of hippocampal afterdischarge under various conditions of stimulation

Abstract

The effect of stimulation parameters on duration of afterdischarge (AD) evoked from the dorsal hippocampus has been studied in the non-anaesthetized rabbit. Repeated hippocampal stimulation of an animal on a single day frequently resulted in prolongation of AD in spite of constant conditions of stimulation. Within short series of stimulations, in which the response remained constant, the following observations were made: 1. 1. Variation of the frequency of stimulation from 10–100 c/sec resulted in AD of the same duration. 2. 2. Increase in voltage, beyond the threshold, did not substantially influence the duration of AD. 3. 3. Hippocampal discharge is observed during stimulation. Under prolonged stimulation, hippocampal discharge comes to an end while stimulation continues. The period from the beginning of stimulation to the end of the hippocampal discharge is constant and not dependent on duration of stimulation. 4. 4. In a given animal AD evoked from different points of both dorsal hippocampi i of the same duration. 5. 5. The duration of hippocampal AD appears to be independent of stimulation parameters over a wide range. It is suggested that this may be a general characteristic of epileptic afterdischarge.