Habituation of rapid sympathetic response to aversive timbre eliminated by change in basal sympathovagal balance.

We studied the difference in the habituation of the rapid sympathetic response to slightly and highly aversive timbres in 68 males. We measured the decrease in the blood volume pulse amplitude (BVP response) as the rapid sympathetic response and the low- (0.04-0.15 Hz) to high- (0.15-0.40 Hz) frequency (LF/HF) ratio of heart rate variability as the sympathovagal balance. The BVP response was suppressed for slightly aversive timbres that had been presented once before, but not for a highly aversive timbre. In contrast, the prior presentation of a highly aversive timbre enhanced the BVP response to a slightly aversive timbre. Only a highly aversive timbre reduced the LF/HF ratio. We suggest that the lack of habituation of the rapid sympathetic response to an aversive timbre is the result of the balance between the effects of the increase caused by the change in sympathovagal balance to vagal dominance and the decrease caused by classical habituation.