Vagal withdrawal as a function of audience.

This investigation examined the effects of psychosocial influences upon vagal cardiac activity. In this crossover, counter-balanced study, 15 subjects were assessed for vagal cardiac activity before and during a presentation in the presence and/or absence of an audience. Electrocardiograms (ECG) were collected throughout the epochs of interest, using a portable holter monitor system. Power spectral density analyses were used to decompose autonomic rhythmicities of heart rate variability. Significantly diminished vagal power was noted before and during presentation episodes with an audience compared with vagal power during a presentation without an audience (P < 0.05). Because respiration modulates autonomic outflow, ECG-derived respiration was derived and compared for all epochs, and no significant differences were noted. The real-life findings in the current investigation are strongly suggestive of the modulating effects of psychosocial interactions upon vagal cardiac electrophysiology and should be considered when assessing autonomic status.