Age-related differences in recovery cycle of auditory evoked potentials

Age-related differences in cerebral responsiveness to stimuli as reflected by the recovery cycle of cortical auditory evoked potentials (EPs) were investigated in healthy young and elderly adults. Pairs of identical tones separated by a fixed 350 msec interval were presented at rates of 1.0/sec, 0.5/sec, and 0.2/sec (inter-pair-intervals of 650, 1650, or 4650 msec). No age difference in the P1-N1 or N1-P2 amplitudes to either tone of the pair was present with the two faster stimulation rates. However, age-specific amplitude effects emerged for the slowest rate. The P1-N1 and especially the N1-P2 amplitude of the EP to the first as compared to that of the second tone was greatly enhanced among the young, but not as much among the elderly adults. Similarly, group differences in baseline to N1 and P2 amplitude measures of EPs to the first tone of the pair were most pronounced at the fastest stimulation rate. These data indicate clear differences in the recovery cycle of EPs between normal young and elderly subjects and demonstrate the applicability of the two-tone stimulation procedure in the assessment of cerebral responsivity in normal and pathologic populations.