A single bout of aerobic exercise improves executive function; however, the mechanism for the improvement remains unclear. One proposal asserts that an exercise-mediated increase in cerebral blood flow (CBF) enhances the efficiency of executive-related cortical structures. Here, participants completed separate 10-min sessions of moderate to heavy intensity aerobic exercise, a hypercapnic environment (i.e., 5% CO2), and a non-exercise and non-hypercapnic control condition. The hypercapnic condition was included because it produces an increase in CBF independent of metabolic demands. An estimate of CBF was achieved via transcranial doppler ultrasound and near-infrared spectroscopy that provided measures of middle cerebral artery blood velocity (BV) and deoxygenation (HHb), respectively. Exercise intensity was adjusted to match participant-specific change in BV and HHb associated with the hypercapnic condition. Executive function was assessed prior to and after each session via antisaccades (i.e., saccade mirror-symmetrical to a target) because the task is mediated via the same executive networks that demonstrate task-dependent modulation following single- and chronic-bouts of aerobic exercise. Results showed that hypercapnic and exercise conditions were associated with comparable BV and HHb changes, whereas the control condition did not produce a change in either metric. In terms of antisaccade performance, the exercise and hypercapnic - but not control - conditions demonstrated improved post-condition reaction times (RT), and the magnitude of the hypercapnic and exercise-based increase in estimated CBF was reliably related to the post-condition improvement in RT. Accordingly, results evince that an increase in CBF represents a reliable candidate for a post-exercise improvement in executive function.

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Executive function entails high-level cognitive control supporting activities of daily living. Literature has shown that a single-bout of exercise involving volitional muscle activation (i.e., active exercise) improves executive function and that an increase in cerebral blood flow (CBF) may contribute to this benefit. It

Executive function supports the rapid alternation between tasks for online reconfiguration of 2 attentional and motor goals. The oculomotor literature has found that a prosaccade (i.e., saccade 3 to veridical target location) preceded by an antisaccade (i.e., saccade mirror-symmetrical to a 4 target) elicits an increase in reaction time (RT), whereas the converse switch does not. This 5 switch-cost has been attributed to the antisaccade task's requirement of inhibiting a prosaccade 6 (i.e., response suppression) and transforming a target's coordinate (i.e., vector inversion) -7 executive processes thought to contribute to a task-set inertia that proactively interferes with the 8 planning of a subsequent prosaccade. It is, however, unclear whether response suppression and 9 vector inversion contribute to a task-set inertia or whether the phenomenon relates to a unitary 10 component (e.g., response suppression). Here, the same stimulus-driven (SD) prosaccades (i.e., 11 respond at target onset) as used in previous work were used with minimally delayed (MD) 12 prosaccades (i.e., respond at target offset) and arranged in an AABB paradigm (i.e., A=SD 13 saccade, B=MD saccade). MD prosaccades provide the same response suppression as 14 antisaccades without the need for vector inversion. RTs for SD task-switch trials were longer 15 and more variable than their task-repeat counterparts, whereas values for MD task-switch and 16 task-repeat trials did not reliably differ. Moreover, SD task-repeat and task-switch movement 17 times and amplitudes did not vary and thus demonstrates that a switch-cost is unrelated to a 18 speed-accuracy trade-off. Accordingly, results suggest the executive demands of response 19 suppression is sufficient to engender the persistent activation of a non-standard task-set that 20 selectively delays the planning of a subsequent SD prosaccade.

IntroductionCognitive flexibility represents a core component of executive function that promotes the ability to efficiently alternate—or “switch”—between different tasks. Literature suggests that acute stress negatively impacts cognitive flexibility, whereas a single bout of aerobic exercise supports a postexercise improvement in cognitive flexibility. Here, we examined whether a single bout of aerobic exercise attenuates a stress-induced decrement in task-switching.Materials and MethodsForty participants (age range = 19–30) completed the Trier Social Stress Test (TSST) and were randomized into separate Exercise or Rest groups entailing 20-min sessions of heavy intensity exercise (80% of heart rate maximum via cycle ergometer) or rest, respectively. Stress induction was confirmed via state anxiety and heart rate. Task-switching was assessed prior to the TSST (i.e., pre-TSST), following the TSST (i.e., post-TSST), and following Exercise and Rest interventions (i.e., post-intervention) via pro- (i.e., saccade to veridical target location) and antisaccades (i.e., saccade mirror-symmetrical to target location) arranged in an AABB task-switching paradigm. The underlying principle of the AABB paradigm suggests that when prosaccades are preceded by antisaccades (i.e., task-switch trials), the reaction times are longer compared to their task-repeat counterparts (i.e., unidirectional prosaccade switch-cost).ResultsAs expected, the pre-TSST assessment yielded a prosaccade switch cost. Notably, post-TSST physiological measures indicated a reliable stress response and at this assessment a null prosaccade switch-cost was observed. In turn, post-intervention assessments revealed a switch-cost independent of Exercise and Rest groups.ConclusionAccordingly, the immediate effects of acute stress supported improved task-switching in young adults; however, these benefits were not modulated by a single bout of aerobic exercise.