Abstract
Nearly a century ago, the first human measurements of brain activity using electroencephalography (EEG) identified oscillatory neural rhythms over parietal cortex between the frequencies of 8 and 14 Hz—the so-called alpha rhythm. However, despite extensive research linking alpha-band oscillations to psychological processes such as controlled knowledge access and attentional selection, the extent to which alpha-rhythms vary across states (e.g., cognitive load) has remained subject to debate. In addition, changes in alpha-band oscillations have been associated with aging possibly as a result of white-matter degeneration in regions within the default mode network (DMN), but most of this work has examined resting alpha and not task-related alpha. Here we compared alpha-band oscillations across two different age groups, younger (n = 30; 18-30 years) and older (n = 30; 57-90 years), in terms of both between-group measures of alpha power and individual variation in peak alpha frequency (PAF). We measured alpha-band oscillations across four tasks associated with increasing cognitive load: resting with eyes closed, resting with eye open, passive visual oddball, and active visual oddball. Across tasks there appeared to be overall lower PAF and alpha power in the older age group. Age also appeared to interact with increased cognitive load (i.e., across tasks). Aging affects communication within the DMN as well as other areas of the brain used in task-related activities associated with attentional control. Age may also reduce the ability of the brain to modulate alpha-band oscillations to mediate ongoing internally directed cognitive processes.