Diffuse Afterdischarges Following Stimulation of the Fimbria Hippocampi

Abstract

Strong, long-lasting cortical and cerebellar afterdischarges were recorded following weak, repetitive stimulation of the fimbria and hippocampal commissure, in guinea pigs and cats. The projections of the anterior thalamic nuclei to the limbic cortex, short or long intercortical connections and the corpus callosum are not instrumental in the transmission of these effects for either the cerebral or the cerebellar cortex. Only complete transection of the midbrain prevents the cerebellar response. The afterdischarges can still be recorded in the absence of the cellular layers of the neocortex and cerebellum. The findings as a whole indicate a powerful convulsant influence of fimbrial stimulation on the brain of the animals studied. The possible significance is briefly discussed.