Prior self-control exertion decreases pre-frontal cortex oxygenation during a CO2 rebreathing challenge but does not affect perceptions of dyspnoea or tolerance time

Introduction: Dyspnoea perception is influenced by a complex interplay of physiological, psychological, and environmental factors. Recently, we showed that males with high trait self-control experience less dyspnoea and persist for longer in a carbon dioxide (CO2) rebreathing challenge than males with low trait self-control. As selfcontrol can also vary within individuals (state self-control), the primary aim of the present study was to investigate whether prior self-control exertion influenced perceptions of dyspnoea and tolerance of a CO2 rebreathing challenge in healthy young males. We also used functional near-infrared spectroscopy (fNIRS) to assess haemodynamic activity of the pre-frontal cortex (PFC) which is a region of interest (ROI) in dyspnoea research, and the primary brain region associated with exertion of self-control. Methods: In a within-subjects design, fifteen healthy young males completed an easy (congruent) Stroop task (control condition) and a difficult (incongruent) Stroop task (prior self-control exertion, experimental condition) followed by a CO2 rebreathing challenge until the limit of tolerance. Changes in oxyhaemoglobin (Delta O(2)Hb) and deoxyhaemoglobin (Delta HHb) were assessed continuously in the Stroop task and CO(2 )rebreathing challenge. During the CO(2 )rebreathing challenge, dyspnoea intensity and unpleasantness were rated every 30 s. Results: Prior self-control exertion did not affect perceptions of dyspnoea or tolerance time in the CO2 rebreathing challenge (all P > 0.05). Delta O(2)Hb from baseline was higher in the left (+38 %) and right (+44 %) pre-frontal cortices during the difficult Stroop task than the easy Stroop task (both P < 0.05). During the subsequent CO2 rebreathing challenge, Delta O(2)Hb was attenuated following prior self-control exertion in the left PFC. Conclusions: Although prior self-control exertion decreased pre-frontal cortex oxygenation during a subsequent CO2 rebreathing challenge, there was no change in tolerance time or perceptions of dyspnoea.