Author(s): CORYN, N., ARENALES, L., DE PAUW, K., MARUSIC, U., ROELANDS, B., Institution: VRIJE UNIVERSITEIT BRUSSEL, Country: BELGIUM, Abstract-ID: 897

INTRODUCTION:
Mental fatigue (MF) is a psychobiological state resulting from prolonged cognitively demanding activity. MF negatively affects cognitive and physical performance (e.g. attention, executive control, decision-making, reaction time). Yet the underlying mechanisms remain uncertain. MF has been associated with altered brain neurotransmission, including increased cerebral adenosine accumulation and decreased dopamine levels. However, the role of the noradrenergic system, central to the regulation of attention and arousal, remains largely unexplored in MF. Therefore, we aimed to investigate whether enhancing noradrenergic signalling via reboxetine (REB), a selective noradrenaline reuptake inhibitor, mitigates MF.
METHODS:
Fifteen healthy young adults (7 males, 8 females, age: 22.1 ± 2.5 years, height: 172.7 ± 8.3 cm, weight: 63.0 ± 9.2 kg) participated in a randomised, triple-blinded, placebo-controlled, crossover study. Cognitive performance was assessed using a Go/No-Go task administered before and after the MF-inducing task, which consisted of a 60-minute Stroop task. Self-reported MF was evaluated using the Mental Visual Analogue Scale (M-VAS) at five time points (baseline, 15, 30, 45 and 60 minutes during the Stroop task). To detect the differences between REB and placebo, mixed-effects models were used to assess the interaction and main effects of the drug and time. The significance level was set at p < 0.05.
RESULTS:
In the Go/No-Go task, no significant effects of drug, time, or their interaction were observed for Go reaction time (p ≥ 0.186). Go and No-Go accuracy significantly decreased over time (p < 0.001), with no drug (p ≥ 0.211) or interaction effects (p ≥ 0.627). For the Stroop task, reaction time showed no significant main effect of drug (p = 0.367) and time (p ≥ 0.102), and there were no significant interaction effects (p ≥ 0.749). The Stroop colour accuracy decreased at 45 (p = 0.028) and 60 minutes (p = 0.028), with no significant drug (p = 0.461) or interaction effects (p ≥ 0.509). Stroop switch accuracy showed no significant effects of drug (p = 0.662), time (p ≥ 0.216), or interaction (p ≥ 0.544). Finally, self-reported MF significantly increased over time (p < 0.001), while REB had no significant effect (p = 0.304).
CONCLUSION:
MF significantly impaired cognitive accuracy and increased self-reported MF. However, noradrenergic modulation via REB did not protect against MF-related declines in cognitive performance. These findings suggest that isolated noradrenergic modulation is insufficient to counteract the MF-related performance decrements, supporting the notion that other neurochemical mechanisms, or interactions between catecholaminergic systems, are more critical in the development and consequences of MF.