Telemetry and continuous energy analysis of hypothalamic eeg changes in female cats during intromission by the male

Abstract

(1) Hypothalamic and cortical macro-electrode (EEG) records were telemetered from freely-moving, ovariectomized cats treated with estrogen during mating tests with males, and records were analysed for EEG energy changes in 3 frequency bands (4–8, 8–16 and 16–32 Hz). The methods used for telemetry and EEG analysis are fully described. (2) Synchronous with the male's intromission, there was a flattening of the amplitude of the already activated EEG (Suppression response) in hypothalamic ventromedial nucleus (Hvm) which was not observed in other hypothalamic or cortical sites. (3) EEG energy analysis showed that the effect was most marked in the 16–32 Hz band, and confirmed that it was localized to Hvm. (4) Similar, but not identical, suppression responses were observed during vaginal probing both before and during estrogen treatment: the response was not, therefore, a hormone-dependent one. (5) The suppression response in Hvm was considered to be a neural correlate of intromission by the male and, together with changes in the background level of the EEG, may play a role in determining the affective responses of the female cat to the male's copulatory activity.