Rapid Mental Fatigue Amplifies Age-Related Attentional Deficits

Deficient information processing with increasing age has been assigned to reduced efficiency in frontal executive control functions. Dopamine has been assumed to play a central role for this decline. Dopamine, however, is also essential for the maintenance of motivation for a longer period of time and is therefore a core factor for mental fatigue. Combining these two findings, we tested to what degree older adults are more prone to performance loss due to increasing time on task than younger adults. Twelve younger and twelve older participants performed an inhibition of return task for 80 min. Performance declined in the older participants but not in the young. Event-related potentials (ERPs) of the EEG, however, showed distinct changes with time on task primarily for young participants. The dissociation between behavioral and ERP results indicates that changes in ERPs of the young participants could reflect adaptations to the task rather than fatigue. This is evident from very distinct changes of the posterior N1 component in this group. The failing (or rather unspecific) adaptation to the task in older adults might have been a consequence of lacking frontal executive control functions reflected in a massive reduction of the N2 component of the ERP, relative to the young participants.