Author(s): SCHAMPHELEER, E., ARENALES ARAUZ, Y.L., DE PAUW, K., MARUSIC, U., ROELANDS, B., Institution: VUB, Country: BELGIUM, Abstract-ID: 1413

INTRODUCTION:
Mental fatigue (MF) is caused by prolonged cognitive activity and negatively impacts cognitive and physical performance. Despite its prevalence, the underlying neurochemical mechanisms remain poorly understood. Dopamine has been implicated in MF development, with theories suggesting that prolonged cognitive demands may decrease dopamine transmission in brain regions involved in cognitive control. However, direct empirical evidence is lacking. This study examined the effects of dopamine reuptake inhibition on cognitive performance in MF.
METHODS:
In a placebo-controlled, within-subject design, 16 participants (M: 8; 22±3y) completed a mentally fatiguing protocol with placebo (PLA) and methylphenidate (MPH; 20mg; dopamine reuptake inhibitor). MF was induced using a 60min incongruent Stroop task with task-switching, during which cognitive performance was continuously measured. To evaluate the MF impact on subsequent performance, a Go/No-Go task was performed before and after the Stroop task, assessing sustained attention (Go) and response inhibition (No-Go). Primary outcomes were reaction time (RT) and accuracy. Secondary outcomes were subjective MF, sleepiness and perceived workload. Outcomes were analysed using mixed-effects models (p<0.05).
RESULTS:
Go- and No-Go-trial accuracy declined following MF (p=0.04; p<0.001), independent of drug condition (all p>0.18). Go-trial RT remained unaffected by MF (p=0.20) and drug intervention (p=0.42). Throughout the Stroop task, performance on switch-task stimuli was maintained, with overall higher accuracy in MPH versus PLA (p=0.004). For standard colour-naming stimuli, accuracy declined over time in both conditions, however, this decline was attenuated in the MPH condition, with significantly better accuracy after the third (p=0.01) and last block (p=0.03) compared to PLA. RT on colour-naming trials decreased over time, with faster responses at 60 mins (p=0.03), showing no significant MPH effect (p=0.39). Subjective MF increased during the Stroop task (all p<0.001) and was significantly lower under MPH compared with PLA (p<0.001). Sleepiness and workload were significantly lower under MPH (all p=0.003).
CONCLUSION:
MF impaired cognitive control and response inhibition, as evidenced by reduced accuracy on both Go and No-Go trials, without affecting response speed. Dopaminergic modulation did not prevent these transferable MF effects post-task, but selectively preserved accuracy during the sustained Stroop task. The dissociation between improved performance during the MF task and unchanged performance on the subsequent cognitive control task may reflect differences in task nature and difficulty or task-switching effects. Notably, MPH reduced subjective MF, sleepiness, and workload during the prolonged cognitive task. These findings indicate the task-specific nature of dopaminergic influences on cognition and highlight their relevance for maintaining performance during sustained cognitive demands in sport.