Signal Detection and the “Cardiac Arousal Cycle”

Abstract

The hypothesis was tested that different phases of the cardiac cycle would be associated with differences in either sensory capacity or response bias, as estimated by signal detection analyses. Each of 10 subjects was given 800 signal (SN) and 800 non‐signal (N) trials randomly distributed throughout the cardiac cycle. The signal was a 35 msec duration, 1000 Hz tone, which was preceded by a 1 sec warning light. Electrocardiograph (EKG) cycles were subsequently divided into four phases, and the phase during which the SN or N trial fell was determined. Signal detection analyses performed on auditory sensitivity (d.) and estimate of response bias (Criterion Location) showed no measurable effect of EKG phase on either parameter. Results are discussed in terms of recent neurophysiological findings of cardiac rhythmic input to the nucleus tractus solitarius (which can inhibit cortical arousal), but little cardiac rhythm in the observed output. These considerations imply that “cardiac cycle arousal effects” are likely to be minute or nonexistent.