EEG markers of vigilance, task-induced fatigue and motivation during sustained attention: Evidence for decoupled alpha- and beta-signatures

Reduced vigilance can be captured in measures of attentional lapses in sustained attention tasks, but just how these lapses relate to task-induced fatigue and motivation to maintain optimal performance is unclear. We used the sustained attention to response task (SART) to induce fatigue, and manipulated motivation levels for the last block of the task in young and older participants (N = 34), while recording EEG to track electrophysiological markers of vigilance change, fatigue and motivation. Despite significant increases in subjective fatigue and mind wandering over 45 minutes, no vigilance decline was observed. However, the age groups differed markedly in their response strategies from the outset (adopting distinct speed-accuracy trade-off strategies) with faster/more erroneous responses in the younger and slower/more accurate responses in the older participants. The subjective rises in fatigue/mind wandering were coupled with an increase in pre-stimulus alpha-power, whereas the post-stimulus activity revealed two distinguishable beta signatures: a fronto-central topography as a marker of response strategy and a fronto-parietal distribution modulated by motivation per se. Our results thus show three distinct neural patterns underpinning the effects of fatigue, response strategy and motivation and suggest a (motivational) cognitive control mechanism behind resetting of performance decrement, independent of persistent fatigue.