Cardiac cycle phase affect auditory-evoked potentials in response to acoustic startle stimuli, but not perceived intensity ratings

Startle stimuli presented in the early cardiac cycle phase elicit lower responses than stimuli presented in the late cardiac
cycle phase. This effect, named ‚Cardiac modulation of startle (CMS)‘, was proposed to reflect baro-afferent signal processing
in the central nervous system. It is yet unclear, however, whether the CMS is due to a general sensory attenuation
effect by baro-afferent signal transmission or to a specific neural pathway that selectively attenuates startle stimulus
processing, but may eventually enhance other processes. The aim of the present study was, therefore, to address this
issue. In this present study 23 female participants were presented acoustic stimuli of varying intensities (95, 100, and 105
dBA) during early (R-wave + 230 ms) and late (R+ 530 ms) cardiac cycle phase. Startle responses (EMG of the M. Orbicularis
Oculi), auditory-evoked potentials (AEPs), and perceived intensity ratings of all stimuli were assessed. Higher startle
stimulus intensities evoked higher perceived intensity ratings, stronger EMG startle responses, and higher N1, P2, and P3
AEPs. Startle stimuli in the early cardiac cycle phase elicited lower startle responses, and a positive shift of the N1 and P3
components as compared to the late cardiac cycle phase. Intensity ratings were unaffected by the cardiac cycle phases.
The present AEP pattern associated with CMS appears to be unique across all startle modulation paradigms, supporting a
more specific neural pathway, rather than a general sensory attenuation.