Pupillometric indices of locus-coeruleus activation are not modulated following single bouts of exercise

Abstract

Single bouts of exercise have been observed to enhance numerous domains of cognition including inhibitory aspects of cognitive control and neuroelectric indices of attention. Given that the locus-coeruleus norepinephrine system regulates alertness and attention, this system may underlie these exercise-induced enhancements. The present study used pupillometry to examine the extent to which a single bout of exercise induces changes in aspects of locus-coeruleus activation, as well as the extent to which changes in locus-coeruleus activation were associated with changes in inhibition and neuroelectric indices of attention. Using a within-participants crossover design, behavioral, neuroelectric, and pupillometric measures were assessed in response to an inhibitory control task before and after 20-min of either aerobic exercise or an active-control condition during two separate, counterbalanced sessions. The aerobic exercise condition consisted of walking/jogging on a motor driven treadmill at an intensity of approximately 70% of age-predicted maximum heart rate. The active control condition consisted of walking on the treadmill at 0.5 mph and 0% grade. Replicating prior findings, enhancements in both reaction time and neuroelectric indices of attention were observed in response to the exercise condition. However, neither the exercise nor the active control conditions were observed to induce changes in activation of the locus-coeruleus as indexed by pupil size, and changes in activation of the locus-coeruleus were not associated with exercise-induced changes in inhibition and neuroelectric indices of attention. Accordingly, these findings provide evidence to suggest that activation of the locus-coeruleus is not a mechanism underlying exercise-induced enhancements in cognition.