Breathing in synchrony: Exploring neural-visceral effects in Su-soku breath counting

Meditation is a mental practice centered on focused attention and awareness. It often involves mindful breathing: attending to the flow of air into and out of the body. Mindful breathing is associated with improvements in mental well-being and cognitive function. However, mindfulness meditation can be challenging, especially those with mental health difficulties. In this study we investigated whether a single session of “Su-soku” – a traditional breath-counting exercise – would have measurable effects on central and autonomic correlates of attentional focus. Our primary prediction was that Su-soku would tend to increase induced theta oscillations during an auditory oddball task. Forty one healthy participants performed a pair of probe tasks (auditory oddball; eyes-open rest) three times: at baseline; after the first “intervention” task (Su-soku or a control task); and after the second “intervention” task (intervention task order counterbalanced across participants). Frontal-midline central nervous system activity was recorded using electroencephalography (EEG). Heart Rate Variability (HRV) indices of autonomic function were computed from electrocardiogram traces recorded via wrist electrodes. We found no evidence that induced theta during the oddball task increased after Su-soku, but did find evidence of increased cardiac deceleration, indicating greater parasympathetic responsivity. HRV indices from the eyes-open rest period also indicated a greater shift towards parasympathetic dominance after Su-soku than after the control task. Frontal-midline oscillatory power in theta, alpha, and beta frequencies, and indices of parasympathetic activity, increased during Su-soku meditation relative to the previous period of Eyes-Open rest, and tended to peak towards the end of exhalation. These results indicate that even a single short session of Su-soku practice can shift autonomic balance in the direction of parasympathetic dominance. The study also provides insights into neural-respiratory interactions during focused breathing, potentially laying the groundwork for future accessible mindful breathing therapeutic interventions in mental health.