Amnesia produced in cats by local seizure activity initiated from the amygdala

Cats were thoroughly trained to enter a small compartment for food. They then received an aversive mouth-shock while eating in the compartment. All cats used as controls showed great hesitation for entering the compartment when tested 24 hr subsequent to such a stimulus. When tonic-clonic convulsions were induced by stimulation applied across the brain, either alone or within 4 sec after an aversive mouth-shock, they unhesitantly entered the compartment 24 hr later, thus displaying full amnesia for the experience, and absence of aversiveness for the convulsion. Convulsions per se, however, are insufficient to produce such amnesia since cats subjected to mouth-shocks followed by tonic-clonic seizures initiated from the frontal cortex or clonic seizures from stimulation of the mesencephalic reticular formation had the same hesitancy as did control animals and thus presumably remembered the punishment. On the other hand, amnesia was produced if, within 4 sec after the mouth-shock, electrical afterdischarges without the production of overt convulsions were initiated by stimulation of the dorsal hippocampus or amygdala; but not if initiated from the septum, fornix, or ventral hippocampus. Present interpretation is that near normal function in the amygdala is necessary for fixation of an aversive experience, and that seizure activity must engage it fully to produce amnesia for such an experience.