Changes in theta and alpha oscillatory signatures of attentional control in older and middle age.

BACKGROUND: Recent behavioural research has reported age-related changes in the costs of refocusing attention from a temporal (rapid serial visual presentation) to a spatial (visual search) task. Using magnetoencephalography, we have now compared the neural signatures of attention refocusing between three age groups (19-30, 40-49 and 60+ years) and found differences in task-related modulation and cortical localisation of alpha and theta oscillations. Efficient, faster refocusing in the youngest group compared to both middle age and older groups was reflected in parietal theta effects that were significantly reduced in the older groups. Residual parietal theta activity in older individuals was beneficial to attentional refocusing and could reflect preserved attention mechanisms. Slowed refocusing of attention, especially when a target required consolidation, in the older and middle-aged adults was accompanied by a posterior theta deficit and increased recruitment of frontal (middle-aged and older groups) and temporal (older group only) areas, demonstrating a posterior to anterior processing shift. Theta but not alpha modulation correlated with task performance, suggesting that older adults' stronger and more widely distributed alpha power modulation could reflect decreased neural precision or dedifferentiation but requires further investigation. Our results demonstrate that older adults present with different alpha and theta oscillatory signatures during attentional control, reflecting cognitive decline and, potentially, also different cognitive strategies in an attempt to compensate for decline.