Infra-slow frequency oscillations propagating through multiple organs convey information on phase-specific timing for self-initiated actions

Cognitive functions crucial for voluntary actions fluctuate with infra-slow frequencies (ISF, <0,2 Hz), indicating their potential impact with self-driven behavior. ISF's involvement in brain-body interaction suggests that the link between ISF oscillations and self-initiated actions can be explored through low-frequency physiological readouts in peripheral organs. Based on these insights, we investigated if ISF in peripheral systems relates to spontaneous motor activity. We analyzed pupillary hippus, heart RR intervals, and respiration against self-paced button presses across various ISF frequencies in 16 participants. Our results were validated with a second dataset of 25 healthy individuals. Self-initiated actions were more likely to occur within a specific phase of the slow3 ISF band (0.073-0.198 Hz) across all observed organ systems. We found phase-locking in the slow3 across those physiological signals, indicating synchronized ISF oscillations spreading throughout the body. The phase locking of spontaneous actions is not distributed randomly. At certain phases of ISF slow3 oscillations, self-initiated actions prevail. This suggests that determined ISF oscillations detectable in the autonomic nervous system relate to when we act. Further exploration of this pathway could deepen insights into the complexities of conscious action initiation. The study did not measure the timing or presence of conscious intention and therefore cannot determine whether conscious will is the final trigger for action.