AUTOMATIC AND EFFORTFUL PROCESSES IN AUDITORY MEMORY REFLECTED BY EVENT-RELATED POTENTIALS - AGE-RELATED FINDINGS

Mismatch negativity (MMN) and N2b were elicited during a selective dic hotic-listening task in 16 young (Y), 16 middle-aged (M) and 19 elderl y (E) subjects to evaluate automatic and effortful memory comparison o f auditory stimuli. Sequences of standard (80%) and deviant (20%) tone s were dichotically presented to subjects in two runs. In each run, su bjects were instructed to give a button-press response to the deviant (target) tones in the ear designated as attended and to ignore the inp ut to the other ear. Peak latencies, peak amplitudes and mean amplitud es were calculated for MMN and N2b components in each subject. MMN lat ency and amplitude were quite stable regardless of age, while N2b late ncy was significantly longer in M and E subjects than in Y subjects. T hese results are interpreted as reflecting that automatic processes of comparison in auditory memory of stimuli presented at short interstim ulus intervals remain quite stable from 23 to 77 years of age; however , those requiring attentional effort decline with age. (C) 1998 Elsevi er Science Ireland Ltd. All rights reserved.