As part of an ongoing study of age-related changes in auditory processing, sensitivity to small changes in
frequency were assessed using the cortical
auditory evoked potential, P1-N1-P2, in younger and
older adults with normal hearing. Behavioral measures have shown age-related differences in
intensity and
frequency discrimination that are larger at lower than higher
frequencies. However, substantial individual differences and equivocal results among studies have been reported. This variability may reflect differences in tasks and procedures, as well as subject variables, such as
hearing sensitivity and level of attention. To minimize these subject variables, the P1-N1-P2 response was investigated using a passive listening paradigm. Subjects were 10 younger and 10
older adults. The P1-N1-P2 was elicited by a 150-ms change in
frequency in otherwise continuous 500-Hz and 3000-Hz
pure tones presented at 70dB SPL. P1-N1-P2 threshold was defined as the smallest change in
frequency needed to evoke a P1-N1-P2 response. Furthermore, a frequency-dependent
aging effect was observed for P1-N1-P2 thresholds, such that older subjects were significantly less sensitive to the
frequency change than younger subjects, with significantly larger age-related differences at 500Hz than at 3000Hz. Age-related changes in response latencies and amplitude of the P1-N1-P2 response were also evident at 500 and 3000Hz. These results are consistent with age-related changes in the
central auditory system and suggest that changes in
frequency discrimination abilities of
older adults may be, in part, related to changes in preattentive levels of auditory processing.
