FOREBRAIN INFLUENCES ON AN AMYGDALOID ACUTE FOCUS IN CAT

Amygdaloid activity was recorded in immobilized, artifically ventilated cats, after induction of an acute epileptogenic focus in the nucleus basalis amygdalae followed by electrical stimulation of the head of the caudate nucleus of the medial septal nuclei and of the nucleus accumbens. Septal stimulation at low frequency induced a driving in the amygdaloid spiking, but at high frequency it invariably evoked a seizure. Low frequency caudate stimulation had no detectable effect on amygdala activity even when, by increasing stimulation voltage to 25 V, cortical spindles were elicited. With high frequency (> 30 Hz, > 1.5 V) the caudate exerted a prolonged inhibitory influence on interictal epileptiform activity of the homolateral amygdala. Contrary to the initial effect, a delayed effect was often observed after both septal and caudate stimulation. Accumbens stimulation at low frequency occasionally induced a driving in the focal spiking, but at high frequency had no detectable effect. Septal stimulation may result in acetylcholine release in the amygdala, and the different effects of caudate stimulation at various frequencies probably indicate frequency-related preferential activation or inhibition of individual neuronal systems within the caudate nucleus.