Slow-Paced Breathing Modulates Perceptual Sensitivity to Facial Expression

Continuous interactions between respiration and cortical rhythms influence how individuals adaptively perceive their environment. However, the intricate relationship among respiration, cortical rhythms, and perceptual function remains elusive. Breathing is a flexible process that can be partially voluntarily controlled. This study leveraged this unique characteristic to probe how brain-respiration interactions coordinate visual perception. Participants performed normal- or slow-paced breathing while discriminating fearful and neutral expressions presented during the midpoint of ongoing inspiration or expiration. The behavioral results showed that compared to normal-paced breathing, perceptual sensitivity was decreased during expiration but increased during inspiration during slow-paced breathing. The corroborating cortical dynamics, as detected by magnetoencephalography, identified perceptual sensitivity-related neural correlates that mirrored the behavioral results. These correlates emerged in the prestimulus period and were predominantly manifested within the alpha/beta frequency range. Subsequent analyses suggest that this observed pace-dependent effect is mediated across a hierarchy of time-frequency scales. First, compared to normal-paced breathing, slow-paced breathing reduces prestimulus theta phase coherence due to diminished respiration-brain phase synchronization. Consequently, the theta phase becomes weakly entrained, thereby preserving resources for long-range communication with response-related networks during slow-paced expiration rather than inspiration, as evidenced by enhanced phase-power coupling. In turn, this cortical adjustment differentially modulates response-related power and ultimately produces decreased or increased perceptual sensitivity during slow-paced expiration or inspiration, respectively. Our overall results elucidate how voluntarily controlled breathing pace may represent a top-down mechanism that influences visual perception.