Age-related changes in binaural processing: I. Evoked potential findings.

Possible age-related effects of speech competition in one ear on the late auditory (LAEP) and P300 event-related potentials recorded at the other ear were investigated with female volunteers. In each of the age categories of 20 to 34, 35 to 49, 50 to 64, and 65 to 80 years, 10 subjects were tested. While contralateral speech competition produced no significant amplitude or latency changes in the earlier auditory brainstem or middle latency responses, several age- and competition-related effects were observed with the later-occurring LAEP and P300 responses. With contralateral competition, the two oldest groups exhibited significantly larger reductions in the N1-P2 peak-to-peak amplitude of the LAEP than did the two youngest groups. While significant decreases in P300 amplitude also occurred with the competition, the magnitude of this effect was not age-related. In addition, small but statistically significant increases in the latency of all three major components, N1 and P2 of the LAEP, and P300, occurred in the presence of contralateral competition. These effects also did not differ among the four age groups. Thus, the LAEP appears to be sensitive to some form of age-related change in binaural processing or attention, although the P300, while sensitive to contralateral competition, did not reflect an age-related component in this effect.