Paced Breathing Associated With Pupil Diameter Oscillations at the Same Rate and Reduced Lapses in Attention.

A dynamical systems model proposes that respiratory, locus coeruleus-noradrenaline (LC-NA), and cortical attentional systems interact, producing emergent states of attention. We tested a prediction that fixing respiratory pace (versus spontaneous respiration) stabilizes oscillations in pupil diameter (LC-NA proxy) and attentional state. Primary comparisons were between 'Instructed Breath' (IB) and 'No Instructed Breath' (NIB) groups. Secondarily, we investigated the effects of shifting respiratory frequency in the IB group from 0.15 to 0.1-0.15 Hz in Experiment 1 (n = 55) and 0.15-0.1 Hz only in Experiment 2 (n = 48) (replication). In the Paced Auditory Cue Entrainment (PACE) task, participants heard two auditory tones, alternating higher and lower pitches, cycling continuously. Tones acted as a breath guide for IB and an attention monitor for both groups. Participants gave rhythmic mouse responses to the transition points between tones (left for high-to-low, right for low-to-high). We derived accuracy of mouse click timing (RTm), variability in click timing (RTVL), and counts of erroneously inverting the left/right rhythm (IRs and Switches). Despite no differences between groups in RTm or RTVL, IB committed significantly fewer IRs and switches, indicating less lapses in attention during paced breathing. Differences in behavioral metrics were present across tone cycle frequencies but not exclusive to IB, so breath frequency did not appear to have a specific effect. Pupil diameter oscillations in IB closely tracked the frequency of the instructed breathing, implicating LC-NA activity as being entrained by the breath intervention. We conclude that pacing respiratory frequency did stabilize attention, possibly through stabilizing fluctuations in LC-NA.