Abstract
Memory changes are commonplace over the lifespan. With advances in neuroimaging there is accumulating evidence that changes in neural dynamics may underscore changes in memory functioning. Oscillations in the theta range have long been associated with memory processes. However, how theta activity might relate to the ageing brain, and more specifically the losses in memory thought to occur during the ageing process, is less clear. This research aimed to explore these questions by analysing a large dataset of 227 adult participants from across the lifespan. Memory was assessed across different domains (episodic, associative, and working memory), and was compared with participants underlying resting-state electroencephalography (EEG). Older participants displayed significant losses in memory performance across all memory domains, as well as decreased theta power across frontal, medial parietal, and occipital regions. Amongst younger participants working memory correlated with theta power in medial frontal, left temporal, and right temporoparietal regions, however this effect was lost amongst older adults. These findings suggest that resting theta power diminishes over the lifespan in numerous cortical regions, which corresponds with a decline in memory performance. Moreover, these findings suggest a nuanced relationship between working memory and theta power, providing evidence of a unique association between theta power and working memory performance only amongst younger adults. Taken together, resting-state EEG measures appear to carry promise in understanding the nature of neurodynamic changes over the lifespan, with theta functioning dynamically changing as a function of age. Whilst this study is limited by its cross-sectional and correlational design, future longitudinal and causational research, possibly using non-invasive brain stimulation, would help clarify the effects observed.