Investigating an interplay between respiration and attention via the locus coeruleus - noradrenaline system

Abstract

The intricate interplay between respiration and attention, a cornerstone of yogic practices for millennia, is now gaining recognition in contemporary cognitive neuroscience. Recent research is shedding light on how respiration influences and is influenced by cognitive processes, suggesting that our respiratory rhythm may serve as a physiological pacemaker for higher order functions. While various sensory cognitive domains have been explored in this context, attention has received comparatively little investigation. A dynamical systems model proposed by Melnychuk et al. (2018) attempted to connect respiration and attention via the locus coeruleus noradrenaline (LC NA) system. This thesis aimed to bolster initial evidence supporting synchronisation between these systems and to test the model's predictions. The first empirical chapter investigated whether decreasing respiratory frequency would stabilise behavioural attention and pupil diameter (PD) oscillatory activity, serving as a proxy measure for LC activity. The study introduced a novel task, the Paced Auditory Cue Entrainment (PACE) task, where participants responded rhythmically to auditory cues while controlling their respiration at 0.1 0.15 Hz range. Results showed that decreasing respiratory frequency mitigated attentional lapses (compared to spontaneously breathing controls), as well as entraining PD oscillations to respiratory frequency. These findings suggest that stabilising fluctuations in LC activity via slow paced respiration might underlie observed improvements in attention. The second empirical chapter explored how attention fluctuates over the respiratory cycle in a sustained attention task for younger (YAs) and older adults (OAs), who have been shown to differ in their attentional strategy in this paradigm. Both YAs and OAs exhibited entrainment of their respiratory cycle to task events, with OAs showing a greater degree. Task performance, subjective attentional state, PD, and EEG oscillatory power all varied significantly over the respiratory cycle, being more conducive for task focus during the entrainment period less conducive outside of it. Modulation patterns differed according to entrainment level and age group, demonstrating bottom up entrainment and top down attentional influences. These findings indicate respiration's role as an "attentional metronome" via the LC NA system. The third empirical chapter focused on sighs and their role in resetting respiratory variability and transitioning between attentional and arousal states. While sighs played a significant role in resetting respiratory variability, they did not appear to influence task measures of attention. However, a notable association between respiratory task entrainment and sighs suggests their role in facilitating further entrainment. Additionally, PD showed large changes during sighs implicating the LC NA arousal system in this process. In conclusion, this thesis provides compelling evidence for the link between respiration and attention through the locus coeruleus, offering novel methodologies for future investigations. By elucidating the mechanisms underlying this connection, it contributes to our understanding of how bodily processes influence cognitive function.