Characterizing Psychomotor Performance Effects of Cognitive Fatigue

Abstract

Cognitive fatigue (CF) is a state of perceived exhaustion arising from sustained mental effort that is both commonly experienced and consequential. CF negatively affects a broad range of cognitive functions, including working memory, decision making, and attention. It can also impair psychomotor performance, such as the ability to generate timely and accurate goal-directed actions, commonly indexed using reaction time (RT). CF-related psychomotor impairments, including slowed RT, may contribute to the risk of accidents or errors across a range of activities and occupations, including athletics, transportation, construction, and healthcare. Despite this, the mechanisms underlying CF-related psychomotor performance deficits remain poorly understood, and there is limited evidence regarding how these impairments might be mitigated.

This thesis addressed these gaps by systematically investigating the effects of CF on multiple psychomotor processes contributing to RT performance and evaluating a potential intervention to attenuate CF-related deficits. Across four experiments using behavioural and neurophysiological approaches, it was found that stimulus perception, response inhibition, and motor preparation were largely preserved under CF, with the latter showing evidence of compensatory activity. In contrast, response selection was found to be selectively vulnerable to CF, with the degree of disruption depending on the overlap in cognitive demands with recent fatiguing mental work. Taken together, findings suggest that response initiation could play a central role in CF-related RT slowing and may present a key target for future investigation. Finally, a fifth experiment provided promising preliminary evidence supporting further investigation of transcutaneous vagus nerve stimulation as a non-invasive countermeasure for CF-related psychomotor deficits.

Overall, this work advances our understanding of the mechanisms underlying CF-related psychomotor performance impairment by characterizing the effects of CF across multiple stages of psychomotor processing. It also provides preliminary support for tVNS as a potential countermeasure for these deficits. These findings may have particularly relevant implications for safety-critical environments, where even small delays in responding could increase risk.