Abstract
Viewing brain function through the lense of other physiological processes has critically added to our understanding of human cognition. Further advances though may need a closer look at the interactions between these physiological processes themselves. Here we characterise the interplay of the highly periodic, and metabolically vital respiratory process and fluctuations in arousal neuromodulation, a process classically seen as non-periodic. In data of three experiments (N = 56 / 27 / 25 women and men) we tested for covariations in respiratory and pupil size (arousal) dynamics. After substantiating a robust coupling in the largest dataset, we further show that coupling strength decreases during task performance compared with rest, and that it mirrors a decreased respiratory rate when participants take deeper breaths. Taken together, these findings suggest a stronger link between respiratory and arousal processes than previously thought. Moreover, these links imply a stronger coupling during periods of rest, and the effect of respiratory rate on the coupling suggests a driving role. As a consequence, studying the role of neuromodulatory arousal on cortical function may also need to consider respiratory influences.
Significance statement We characterise the interplay of the respiratory rhythm and pupil diameter dynamics as a well-known proxy for arousal. Although we consistently find respiratory modulation of pupillary changes, they were most pronounced during periods of rest (compared to during task performance) and dependent on respiratory rate (deep vs. normal breathing).
Footnotes
The authors declare that there were no competing interests with respect to the authorship or publication of this research article.
The authors would like to thank Karin Wilken, Ute Trompeter, and Hildegard Deitermann for their help with data collection.
DSK is supported by the DFG (grant number KL 3580/1-1) and the IMF (KL 1 2 22 01). JG is supported by the DFG (GR 2024/11-1, GR 2024/12-1). We acknowledge support from the Open Access Publication Fund of the University of Münster. All authors are members of the Scottish-EU Critical Oscillations Network (SCONe), funded by the Royal Society of Edinburgh (RSE Saltire Facilitation Network Award to CK, Reference Number 1963).
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