Abstract
The Inhibition Theory of aging suggests that age-related decline in cognition results from a deficit in top-down inhibitory control, a process critical to efficient and effective use of capacity-limited resources, such as visual working memory (VWM). Evidence supporting this theory can be found in studies of overt attentional control (anti-saccades) and VWM. Covertly shifting attention - inhibiting eye movements while moving attention – is a requirement in many EEG studies, due to the artifacts/noise associated with eye-movements. Thus, this skill becomes an implicit data selection criterion, resulting in the exclusion of participants that are simply unable to control their eye movements. This may pose a significant problem when studying older adults. We investigated the relationship between VWM capacity (k) in older and younger adults and the ability to suppress eye-movements during a Localized Attentional Interference (LAI) task, while EEG was recorded. Eye movements were tracked using electrodes placed above, below and at the outer canthi of each eye. Participants were presented with a search array, containing a single coloured target (T) and distractor (L) among gray place-holders, positioned on an invisible circle, centered around a fixation cross. Despite saccade inhibition training, a number of older adults were unable to inhibit their eye movements. Interestingly, their mean k-estimate was significantly lower than the k-estimate of those elderly participates who could inhibit eye movements. Furthermore, a significant negative correlation was found between percent of trials contaminated by saccades and VWM capacity, but only for the older adults. These results suggest that excluding older adult data sets due to excessive eye movement artifacts may result in systematically rejecting lower performing older adults, misconstruing age-related changes in electrophysiology.
Canadian Institute of Health Research (CIHR).