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

Abstract

Reduced vigilance can be captured as attentional lapses in sustained attention tasks, but just how these lapses relate to taskinduced 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. Post stimulus 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.