Neural activity associated with controlled and automatic attention varies with age, working memory capacity and perceptual load

Behavioral studies in young adults have shown that working memory capacity (WMC), the ability to maintain and manipulate items in memory, may be associated with individual differences in selective attention. Changes in WMC may also reflect reduced controlled attention and/or increased distractibility observed in aging. Age and individual differences in selective attention may be further modulated by bottom-up manipulations of perceptual load. This project assessed the neural basis of age and individual differences in WMC by measuring auditory (N100) and long-latency (P300, slow wave) event-related potentials (ERPs) associated with selective attention. Young (n=29) and older (n=22) adults with high and lower WMC discriminated pure tone targets (1000 Hz) from nontargets at midline. Perceptual load was manipulated using nontarget frequency (low load=500 Hz, high load=950 Hz). White noise distracters were presented at 0° or +/-90˚. Amplitudes of target-P3b, distracter-N100 and P3a under low load, and nontarget slow wave under high load decreased with age. Latencies of target/nontarget N100 and P3b increased with age under low load. High WMC in young showed enhanced target N100 and nontarget slow wave under high load and reduced distracter N100 amplitude. High vs. lower WMC in older conveyed increasing vs. decreasing P3a latency from Fz to Pz, respectively. High WMC in older also conveyed enhanced slow wave over time. Age differences in controlled attention (N100, P3b) automatic orienting (N100, P3a) and sustained attention (slow wave) were modulated by perceptual load and may reflect changes in underlying neural networks. WMC in young were related to individual differences in early attentional (N100) and sustained (slow wave) processing but not later automatic orienting (P3a) or stimulus classification (P3b). WMC differences in older were shown in early automatic orienting (P3a) and sustained attention (slow wave).