Bilateral thermocoagulation of the cingulate gyri produced an abolishment of fear reactions concomitantly with an exaggerated aggressiveness and a drastic impairment of delayed responses. The changes in emotionality subsided after several months but there was no recovery, even after prolonged post-operative training, of the dalayed responses with a 5 min delay. Only partial improvement of the responses with shorter delays (10 sec and 1 min) was observed. This memory deficit is discussed in terms of disruption of neuronal limbic circuits necessary for maintaining the impulse reverberation.