Effects of repeated measures on the late auditory evoked response.

Abstract

A concern in clinical applications of the late auditory evoked response is the variability of amplitude and latency. While there is agreement that less variability is seen within than across subjects, the effects of stimulus and acquisition factors are not fully understood. This project examined the effects of repeated measures and stimulus type [1 kHz tone at 40 and 80 ms and speech (da) at 40 ms] on the amplitude and latency of P1. Latency was measured conventionally while amplitude was measured in two ways: peak-to-baseline (P-B) and peak-to-trough (P-T). Two amplitude measures were obtained because some commercially available instruments provide a P-B measure as the default amplitude. Stimuli were presented to 30 normal hearing young adults at 60 dBnHL. P1 latency increased significantly (p=0.024) from replicate 1 (35.9 ms) to replicate 3 (41.1 ms) for the 40 ms tone but not for 80 ms nor for speech. P-B amplitudes were significantly (p<0.01) smaller than P-T. Also, P-T amplitudes diminished significantly (p<0.01) from replicate 1 to replicate 3 for each stimulus type but P-B amplitudes did not. These findings suggest that P-B and P-T are not identical measures of P1 physiological activity.