Feature processing during visual search in normal aging: Electrophysiological evidence

Laura Lorenzo‐López; Amenedo, Elena; Cadaveira, Fernando · 2007 · OpenAlex-citations

DOI: 10.1016/j.neurobiolaging.2007.02.007

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Summary

This study investigates the specific effects of normal aging on visuospatial attention during visual search, addressing whether age-related deficits stem from a generalized slowing of information processing or a specific impairment in attentional allocation. The researchers utilized event-related potentials (ERPs) to examine the N2pc component, an electrophysiological marker of attention shifts to lateralized targets. Additionally, the study explored whether task-irrelevant, salient stimuli (color singletons) automatically capture attention in both young and older adults, and whether this capture habituates with practice. The experiment involved 17 young adults (mean age 19.6) and 22 older adults (mean age 68.5). Participants performed a visual search task requiring them to detect an orientation-defined target (a vertical bar) among distractors. In some trials, a task-irrelevant color singleton (a red bar) was presented without prior instruction. EEG data were recorded to analyze the N2pc component, which reflects the allocation of attention to the target’s location. The analysis focused on N2pc latency and amplitude for orientation targets, and the presence or absence of N2pc for irrelevant color singletons across six experimental blocks to assess habituation. Behavioral results indicated that older adults had significantly slower reaction times and lower hit rates than young adults. Electrophysiologically, both groups exhibited a consistent N2pc component for orientation targets, but this component was significantly delayed (by approximately 68 ms) and attenuated in older subjects. This suggests that aging specifically slows the shift of visuospatial attention and reduces the amount of attentional resources allocated to targets. Crucially, neither age group showed an N2pc component for the irrelevant color singletons, indicating that these distractors did not capture attention. This lack of capture remained consistent across all experimental blocks, demonstrating no habituation effects. Furthermore, the absence of N2pc for color singletons in older adults suggests that the ability to inhibit irrelevant stimuli is preserved in normal aging. The findings provide the first electrophysiological evidence that normal aging involves a specific slowing and reduction in the efficiency of visuospatial attention allocation, rather than just general processing slowing. The preservation of top-down inhibition against irrelevant distractors in older adults challenges the notion that aging universally impairs the ability to ignore irrelevant information. Instead, it suggests that while the speed and intensity of focusing attention on relevant targets decline with age, the mechanisms for suppressing irrelevant, easily distinguishable distractors remain intact.

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• visual search