Breathing is a vital physiological process essential to human survival, and as expected from such an important function it occurs automatically without the requirement of conscious control. Nonetheless, breathing automatisms can be consciously modified, and is regularly modulated by our conscious experience and consciousness state. However, it remains unclear how consciousness shapes our breathing. In this research project, we employ an interdisciplinary approach, combining basic and clinical neuroscience in order to tackle this fundamental question.
Breathing, despite its deceptive simplicity, is a highly complex behaviour influenced by a variety of external and internal factors. For example, sniff volume decreases after encountering a skunk and increases when smelling fresh bread; Inhalation/Exhalation ratio is altered during speech production, and when playing a wind instrument; Breath magnitude is modified by a melancholy sigh, a scream of fear or a yawn. Respiratory patterns are also highly influenced by consciousness state, presenting an erratic structure during rapid eye movement (REM) sleep and a more regular form in deep non-rapid eye movement (NREM) sleep. This versatile respiratory repertoire results from a combination of conscious and unconscious processes regulating breathing, and is enabled by a dual neural control involving a constant interplay between subcortical and cortical networks. Unconscious automatic breathing is controlled by well-characterized subcortical brainstem respiratory centers. Conscious regulation of breathing, however, and the interaction between involuntary and voluntary respiration control remains unclear. The goal of our research is to characterize the interaction between breathing dynamics and consciousness, and to elucidate the brain mechanism underlying conscious regulation of breathing.
Disorders of consciousness (DoC) offer a unique model to investigate conscious regulation of breathing. DoC resulting from severe brain injury can range from no signs of awareness in vegetative state (VS), also known as unresponsive wakefulness syndrome (UWS), to inconsistent but purposeful and reproducible evidence of conscious awareness in a minimally conscious state (MCS). Notably, DoC can be a chronic condition lasting for many years or an acute reversible state in which patients can gain partial or full consciousness. Thus, DoC offer a rare opportunity to track breathing dynamics during recovery of consciousness and between consciousness states.
Additionally, evidence for conscious control of breathing could be highly beneficial for awareness detection in DoC. Detection of awareness in DoC patients remains one of the most challenging clinical tasks. Misdiagnosis between UWS and MCS has significant therapeutic, ethical and financial implications, and influences end-of-life decisions. We hypothesized that breathing dynamics governed by both autonomic and voluntary control may offer a meaningful indicator for conscious awareness in DoC patients. The specific aims of the proposed research are to:
1) Characterize the relationship between breathing dynamics and consciousness state.
2) Elucidate the neural mechanism underlying conscious control of breathing dynamics.
3) Investigate whether breathing dynamics can be used as an indicator for awareness in DoC patients.
