Cardiorespiratory rhythms, brain oscillatory activity and cognition: review of evidence and proposal for significance

The body is, in essence, an ensemble of interacting systems with biorhythms nested at multiple timescales. Traditionally, the focus in the study of body-brain interaction has been on clarifying the ways by which our brain orchestrates the functions of the body. During recent decades theories building on the opposite causal direction, namely how the different body systems influence the brain and mind, have been dramatically increasing. Despite influential theories, direct research evidence about the link between bodily rhythms, brain and cognition are scattered. Here, we review existing evidence on how the electrophysiological activity of the brain on one hand, and perception or cognition on the other hand depend on the phase of the physiological cycles of the body, specifically those of the heartbeat and respiration. We summarize the accumulated evidence from human and animal studies and their implication for the theoretical reasoning. Last, besides elaborating how the cycles of bodily rhythms influence brain signaling and perceptual cognitive functions, we present potential explanations and answers to why this link might exist.