HIPPOCAMPAL ELECTRICAL-ACTIVITY DURING DEVELOPMENT AND FOLLOWING THE ESTABLISHMENT OF A DOMINANCE-SUBORDINATION RELATIONSHIP IN RABBITS

Hippocampal electrical activity can be modulated by social behaviour. The aim of the present experiment was to study the long-lasting effect s of social interactions on hippocampal EEG. Two male rabbits, implant ed with chronic nichrome electrodes in the hippocampus, were introduce d to an open air, semi-natural environment and their spontaneous behav iour was studied for 3 days. In this period, one of them exhibited dom inant behaviour and the other signs of subordination. Hippocampal elec trical activity was recorded by two high-power telemetry devices, one for each rabbit. The behaviour, recorded by video cameras, and neural activity of both rabbits were videotaped and then analyzed. This metho d allowed simultaneous comparisons between the electrical profiles of dominant-type and subordinate-type behavioural elements. Results show that typical hippocampal electrical patterns can be ascribed to domina nt and subordinate subjects. Behavioural aspects of dominance were obs erved in one of the two animals early in the observations and were con firmed at the end of the experiment after the introduction of an intru der (a male rabbit). The hippocampal electrical activity of the domina nt animal showed an increase of frequency which was evident after the first or second experimental session. Rhythmicity of hippocampal EEG i ncreased in the dominant animals. These electrical variations were par ticularly evident during behavioural elements such as quiet immobility , exploration and interactive behaviour.