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 self-control 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 (ΔO₂Hb) and deoxyhaemoglobin (ΔHHb) were assessed continuously in the Stroop task and CO₂ rebreathing challenge. During the CO₂ 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). ΔO₂Hb 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, ΔO₂Hb 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.