Preserved Suppression of Salient Irrelevant Stimuli During Visual Search in Age-Associated Memory Impairment.

Previous studies have suggested that older adults with age-associated memory
impairment (AAMI) may show a significant decline in attentional resource capacity
and inhibitory processes in addition to memory impairment. In the present paper,
the potential attentional capture by task-irrelevant stimuli was examined in older
adults with AAMI compared to healthy older adults using scalp-recorded event-related
brain potentials (ERPs). ERPs were recorded during the execution of a visual search
task, in which the participants had to detect the presence of a target stimulus that
differed from distractors by orientation. To explore the automatic attentional capture
phenomenon, an irrelevant distractor stimulus defined by a different feature (color) was
also presented without previous knowledge of the participants. A consistent N2pc, an
electrophysiological indicator of attentional deployment, was present for target stimuli
but not for task-irrelevant color stimuli, suggesting that these irrelevant distractors
did not attract attention in AAMI older adults. Furthermore, the N2pc for targets was
significantly delayed in AAMI patients compared to healthy older controls. Together,
these findings suggest a specific impairment of the attentional selection process of
relevant target stimuli in these individuals and indicate that the mechanism of top-down
suppression of entirely task-irrelevant stimuli is preserved, at least when the target and
the irrelevant stimuli are perceptually very different.