Individual Differences in Auditory Electric Responses: Comparisons of Between-Subject and Within-Subject Variability IV.Latency-variability Comparisons in Early, Middle, and Late Responses

Abstract

In this series of reports to date (Lauter & Loomis, 1986, 1988; Lauter & Karzon, 1990 a & b) we have described patterns of relative variability observed in latency and amplitude of auditory brainstem responses (ABRs) collected in a repeated-measures within-subjects design testing two groups of neurologically normal adults. Each of the two groups of subjects was additionally tested for one other type of auditory evoked potential, according to the same schedule of eight weekly sessions: middle-latency responses (MLRs: 10 to 50 ms post-stimulus) were collected from Group II (four females and four males), and late responses (50 to 300 ms post-stimulus) from Group I (four females and three males). This paper presents data comparing and contrasting the patterns of relative variability of waveform-peak latency observed in middle-latency, late responses, and the ABR data previously reported. Results document a trimodal distribution of response latency variability, with ABR peak V in one category, characterized by high within-subject stability and low between-subject stability, ABR peaks II, III, and IV, together with MLR peak No in a second category, of intermediate within-subject stability, and a third category consisting of ABR peak I together with all auditory-evoked-potential (AEP) peaks subsequent to MLR peak No, in which consistency of peak latency calculated within subjects approaches the low level of consistency calculated across subjects.