Abstract
Cardiac activity has been shown to interact with conscious tactile perception: Detecting near-threshold tactile stimuli is more likely during diastole than systole and heart slowing is more pronounced for detected compared to undetected stimuli. Here, we investigated how cardiac cycle effects on conscious tactile perception relate to respiration given the natural coupling of these two dominant body rhythms. Forty-one healthy participants had to report conscious perception of weak electrical pulses applied to the left index finger (yes/no) and confidence about their yes/no-decision (unconfident/confident) while electrocardiography (ECG), respiratory activity (chest circumference), and finger pulse oximetry were recorded. We confirmed the previous findings of higher tactile detection rate during diastole and unimodal distribution of hits in diastole, more specifically, we found this only when participants were confident about their detection decision. Lowest tactile detection rate occurred 250-300 ms after the R-peak corresponding to pulse-wave onsets in the finger. Inspiration was locked to tactile stimulation, and this was more consistent in hits than misses. Respiratory cycles accompanying misses were longer as compared to hits and correct rejections. Cardiac cycle effects on conscious tactile perception interact with decision confidence and coincide with pulse-wave arrival, which suggests the involvement of higher cognitive processing in this phenomenon possibly related to predictive coding. The more consistent phase-locking of inspiration with stimulus onsets for hits than misses is in line with previous reports of phase-locked inspiration to cognitive task onsets which were interpreted as tuning the sensory system for incoming information.
Significance statement Mechanistic studies on perception and cognition tend to focus on the brain neglecting contributions of the body. Here, we investigated how respiration and heartbeat influence tactile perception: We show that inspiration locked to expected stimulus onsets optimizes detection task performance and that tactile detection varies across the heart cycle with a minimum 250-300 milliseconds after heart contraction, when the pulse reaches the finger. Lower detection was associated with reduced confidence ratings, indicating – together with our previous finding of unchanged early ERPs - that this effect is not a peripheral physiological artifact but a result of higher cognitive processes that model the internal state of our body, make predictions to guide behavior, and might also tune respiration to serve the task.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Conflict of Interest: The authors declare no competing financial interest.
