Purpose. Acute bouts of exercise have been found to have an influence on cognitive performance. However, the published literature has yet to narrow down the underlying biological mechanism of "why". In addition to exercise, intranasal insulin (without an effect on peripheral glucose levels) has been found to manipulate glucose uptake in the brain. Therefore, with the use of acute exercise and intranasal insulin, the purpose of this study was to investigate the possible underlying mechanism of cerebral glucose uptake and observe its influence on the relationship between exercise and inhibitory control. Additionally, another aim of this investigation was to establish a dose response relationship between intranasal insulin and cognition.Method. 109 participants (52 exercise, 57 control) were run through a cross-sectional, pre-and post-double-blind design. Each participant was randomized into either an exercise or control (i.e. rest) condition and either a saline control group or an insulin dose group. Inhibitory control performance was evaluated before and after the exercise/rest condition with the intranasal saline/insulin being administered prior to being on the treadmill.Results. For behavioral performance (i.e. reaction time and response accuracy) and neural indices of attention (i.e. P3 amplitude) a 2 (Condition) X 7 (Dose) X 2 (Congruency: congruent, incongruent) univariate multi-level model controlling for the random intercept associated with participants was run. The effects of intranasal insulin were specific to the behavioral indices of attention with no influence on the P3 amplitude at any dose. Faster reaction time was observed in response to 40 (-46.7 ± 32.4) and 80 (-39.3 ± 23.4) IU doses of insulin in comparison to the 0 IU (-3.0 ± 14.2) placebo dose (p's 2264 0.003) and 60 (-5.1 ± 28.3) IU dose (p's 2264 0.005). The 40 IU dose also influenced a faster reaction in comparison to 120 (-9.4 ± 23.3) IU dose (p = 0.002). These significant differences were only observed during the control condition. However, a nonsignificant trend was observed for the exercise condition that revealed a linear relationship of a shorter reaction time as dose increased in contrast to the curvilinear relationship that the control condition showed. No significant differences were observed for response accuracy.Conclusions. With a curvilinear relationship of the change in reaction time in response to dose being observed for the control condition and a linear relationship being observed for the change in reaction time in response to dose for the exercise condition. This preliminary study provides valuable information about intranasal insulin dose and its possible interactions with exercise for future interventions targeted at cognitive performance.
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