Phase-dependent respiratory-motor interactions in reaction time tasks during rhythmic voluntary breathing.

The study investigated squeezing reaction time (RT) in response to a visual cue during rhythmic voluntary breathing at 0.6 Hz paced by a metronome, breath holding, or at rest in 13 healthy subjects. Rhythmic voluntary breathing slowed down RT, only in the expiratory phase with accompanied changes in the length of respiratory phases, while breath-holding reduced RT. The prolonged RT during voluntary expiratory phases and the absence of changes in RT during voluntary inspiratory phases are most likely related to disproportionally increased cognitive demands during the expiratory phase of voluntary breathing. The absence of changes in RT during voluntary inspiration is likely to be compensated by respiratory-motor facilitation mechanisms in this phase. Shortened RT during breath holding is possibly associated with increased attention.