Brain-heart interactions in the neurobiology of consciousness

Abstract

Recent experimental evidence on patients with disorders of consciousness revealed that observing brain-heart interactions helps to detect residual consciousness, even in patients with absence of behavioral signs of consciousness. Those findings support hypotheses suggesting that visceral activity is involved in the neurobiology of consciousness, and sum to the existing evidence in healthy participants in which the neural responses to heartbeats reveal perceptual and self-consciousness. More evidence obtained through mathematical modeling of physiological dynamics revealed that emotion processing is prompted by an initial modulation from ascending vagal inputs to the brain, followed by sustained bidirectional brain-heart interactions. Those findings support long-lasting hypotheses on the causal role of bodily activity in emotions, feelings, and potentially consciousness. In this paper, the theoretical landscape on the potential role of heartbeats in cognition and consciousness is reviewed, as well as the experimental evidence supporting these hypotheses. I advocate for methodological developments on the estimation of brain-heart interactions to uncover the role of cardiac inputs in the origin, levels, and contents of consciousness. The ongoing evidence depicts interactions further than the cortical responses evoked by each heartbeat, suggesting the potential presence of non-linear, complex, and bidirectional communication between brain and heartbeat dynamics. Further developments on methodologies to analyze brain-heart interactions may contribute to a better understanding of the physiological dynamics involved in homeostatic-allostatic control, cognitive functions, and consciousness.

Keywords: Brain-heart interplay; Consciousness; Heart rate variability; Heartbeat-evoked responses; Interoception; Physiological modeling.

Graphical abstract

Fig. 1

The interoceptive-exteroceptive integration: information flux in the neural circuits that may reflect conscious experiences. (1) The processing of information coming from exteroceptive inputs occurs in parallel with (2) the bidirectional communication between the brain and interoceptive channels. (3) The brain integrates the information received from the available sources, exteroceptive and/or interoceptive. The result of these integrations are (4) complex autonomic responses and (5) complex brain responses. An alternative approach to study consciousness is to (6) model possible causal interactions between the complex cardiac activity and brain dynamics.