Hippocampal electrical activity during social interactions in rabbits living in a seminatural environment.

The aim of the present experiment was to study the effect on the electrical activity of the hippocampus of interactions between male rabbits. The behavioral and electrical correlates of social interactions were studied in 13 animals living in a seminatural environment. Rabbits carrying chronic microelectrodes implanted in the hippocampus were introduced singly into a large, natural open air enclosure and their spontaneous behavior observed until they had adapted to the environment. Hippocampal EEG was recorded by telemetry. Subsequently, a second rabbit (intruder) was introduced into the enclosure. Hippocampal EEG and the concomitant behavior of the resident were stored and analyzed. Alerting reactions, approaching and conflictual elements were characterized by typical electrical patterns and parameters. Power spectra of hippocampal EEG showed a significant increase in frequency passing progressively from environment-related behaviors to more specific elements directed towards the intruder. Behavioral elements belonging to the same modality, such as running, chase and flight had different hippocampal EEG frequency distributions. Seven residents showed a clear prevalence of offensive reactions (offensive rabbits) and six defensive elements (defensive rabbits). Defensive animals showed very high frequency levels during nose and flight. Exploration of offensive rabbits in the period preceding and following the introduction of the intruder was characterized by higher EEG frequency values than exploration of defensive animals.