Inhalation boosts perceptual awareness and decision speed.

The emergence of consciousness is one of biology's biggest mysteries. During the past two decades, a major effort has been made to identify the neural correlates of consciousness, but in comparison, little is known about the physiological mechanisms underlying first-person subjective experience. Attention is considered the gateway of information to consciousness. Recent work suggests that the breathing phase (i.e., inhalation vs. exhalation) modulates attention, in such a way that attention directed toward exteroceptive information would increase during inhalation. One key hypothesis emerging from this work is that inhalation would improve perceptual awareness and near-threshold decision-making. The present study directly tested this hypothesis. We recorded the breathing rhythms of 30 humans performing a near-threshold decision-making task, in which they had to decide whether a liminal Gabor was tilted to the right or the left (objective decision task) and then to rate their perceptual awareness of the Gabor orientation (subjective decision task). In line with our hypothesis, the data revealed that, relative to exhalation, inhalation improves perceptual awareness and speeds up objective decision-making, without impairing accuracy. Overall, the present study builds on timely questions regarding the physiological mechanisms underlying consciousness and shows that breathing shapes the emergence of subjective experience and decision-making.NEW & NOTEWORTHY Breathing is a ubiquitous biological rhythm in animal life. However, little is known about its effect on consciousness and decision-making. Here, we measured the respiratory rhythm of humans performing a near-threshold discrimination experiment. We show that inhalation, compared with exhalation, improves perceptual awareness and accelerates decision-making while leaving accuracy unaffected.

The respiratory modulation of interoception.

In a recent article published in The Journal of Neurophysiology titled "Sensitivity to changes in rate of heartbeats as a measure of interoceptive ability," Larsson et al. (J Neurophysiol 126: 1799-1813, 2021) introduce a new method to evaluate the interoceptive ability and report a surprising tendency in humans to perceive fewer heartbeats during spontaneous increases in resting heart rate. The authors argue that this result reflects a reduction in the strength of the heartbeat during the inspiration periods. Here, we discuss this finding and propose a complementary interpretation grounded on consciousness research and an emerging literature showing the influence of the breathing phase on perception and brain activity at rest.