Healthy ageing influences how the shape of alpha and beta oscillations change during reaction time tasks.

Age-related changes to the power and frequency of the brains oscillatory activity have been reported by an extensive literature. In contrast, the influence of advancing age on the shape of oscillation waveforms, a characteristic with increasingly recognised physiological and functional relevance, has not been previously investigated. To address this, we examined the shape of alpha and beta band oscillations from electroencephalography (EEG) data recorded during performance of simple and go/no-go reaction time tasks in 33 young (23.3 {+/-} 2.9 years, 27 females) and 27 older (60.0 {+/-} 5.2 years, 23 females) adults. The shape of individual cycles was characterised using instantaneous frequency, and then decomposed into waveform motifs using principal component analysis. This analysis identified four principal components (one from the alpha band, 3 from the beta band) that were uniquely influenced by the different motor tasks and/or age. These each described different dimensions of shape and tended to be modulated during the reaction phase of each task. However, the way in which each facet of shape varied during the task was unrelated to motor performance, indexed via reaction time, in either group or band. Our results suggest that although oscillation shape is task-dependent, the nature of this effect is altered by advancing age. While these outcomes demonstrate the utility of this approach for understanding the neurophysiological effects of ageing, future work that more clearly links these outcomes with function will be critical.