When the heart meets the mind Exploring the brain-heart interaction during time perception

It has been hypothesized that time estimation relies on bodily rhythms and interoceptive signals, such as heartbeats. Extending previous research demonstrating this connection, we provided further electrophysiological evidence that the brain registers heartbeats while tracking time intervals. We evaluated the heartbeat-evoked potential (HEP) and the contingent negative variation (CNV) during an auditory duration-reproduction task with intervals lasting 4, 8, and 12 seconds and a control reaction-time task employing the exact durations. The (interoceptive) Self-Awareness Questionnaire (SAQ) and the heartbeat-counting task (HCT) were administered. The SAQ, but not the HCT scores, correlated with the mean reproduced durations for 4s, 8s, and 12s intervals: the higher the SAQ score (a stronger awareness of bodily signals), the longer the duration reproductions and the more accurate the timing behavior. The HEP amplitude within 130-270 ms (HEP1) and 470-520 ms (HEP2) after the R peak was smaller for the 4s interval than for the 8s and 12s intervals. This is a timing-specific effect, as the HEP amplitude did not differ for intervals in the reaction-time task. A ramp-like increase in HEP2 amplitudes was significant for the duration-encoding phase of the timing task, but not for the control reaction-time task. The HEP2 increase within the reproduction phase of the timing task correlated significantly with the reproduced durations for the 8s and the 12s intervals. The larger the registered increase in the HEP2, the greater the under-reproduction of the estimated duration. The initial and late CNV components were significantly more negative during the encoding phase than during the reaction-time task. Given the link between these components with attention modulation and temporal memory, we interpret the CNV findings as indicating greater executive resources oriented towards time. We conclude that interoceptive awareness (SAQ) and state-like cortical responses to the heartbeat (HEP) predict duration reproductions, emphasizing the notion of the embodiment of time.