Age-related laterality shifts in auditory and attention networks with normal ageing: Effects on a working memory task

Our brains respond to age-related anatomical and physiological changes by reorganizing functions through increases in activity or laterality shifts, among other possibilities. In suboptimal conditions such as in a noisy environment, the impact of ageing on brain functions is likely to be most apparent. The present study examined the effects of normal ageing on the neural activity associated with working memory (WM) tasks performed in quiet (WMQ) and in noise (WMN). Participants of two different age groups (mean age of 29.9 years and 54.8 years) underwent fMRI scans while performing WMQ and WMN tasks. Behavioural findings reveal that, on average, older adults performed less accurately than younger participants across all tasks combined. Specific comparisons between WMQ and WMN tasks revealed that younger participants performed better in the WMN and older participants performed better in the WMQ. fMRI results reveal increased activity in older participants in regions of the right superior temporal gyrus (STG), right Heschl's gyrus (HG) and left thalamus in WMQ. During WMN tasks older participants demonstrate increased activity in the left STG, left middle temporal gyrus and bilateral thalamus. There was also a laterality shift with increasing age. Areas involved in this laterality shift in the WMQ task included the STG, HG and cerebellum. In the WMN task the areas demonstrating a laterality shift were the STG, HG, cerebellum and thalamus. Findings support the hypothesis that functional networks related to memory processing undergo brain reorganization during ageing. Findings also suggest that the demand on attentional resources increases to compensate for the effects of background noise in both ages studied. These findings contribute to the growing evidence that with ageing is a global reorganization in the functional neural networks associated with cognitive processing.