Strategy and Motivation, Rather Than Fatigue, Drive Age-Related Differences in Sustained Attention Performance: Evidence for Decoupled Beta-Band Oscillations.

Reduced vigilance can be captured as attentional lapses in sustained attention tasks, but just how these lapses relate to task-induced fatigue and motivation to maintain optimal performance across the age span is unclear. We induced fatigue in 18 young (mean age = 22.6 years) and 16 older participants (mean age = 66.5) using the Sustained Attention to Response Task while simultaneously recording electroencephalography (EEG). In the final block, we manipulated motivation levels in half of the participants by offering a financial incentive for best overall performance. We found that the young and older adults differed markedly in their response strategies from the outset (adopting distinct speed-accuracy trade-off strategies) with faster/more erroneous responses in the young adults and slower/more accurate responses in the older participants that remained stable over the experiment, while subjective fatigue increased irrespective of group. Poststimulus EEG activity showed two distinguishable beta signatures: a fronto-central topography as a marker of the age-specific response strategy and a fronto-parietal signal modulated by motivation per se. We speculate that these two signatures contribute to offsetting performance declines over time. Finally, although subjective fatigue or mind-wandering scores and prestimulus alpha power increased with time-on-task, we did not identify a correlation between these measures. Hence, strategy and motivation more than fatigue were associated with performance differences across age in a sustained attention task, reflected in decoupled beta signatures.