Middle-latency responses. II. Variation among stimulation sites.
Burton MJ., Miller JM., Kileny PR.
We investigated the relationship between thresholds of the electrically evoked auditory brain-stem response (EABR) and the electrically evoked middle-latency response (EMLR), and the variation in EMLR thresholds and dynamic ranges with site of stimulation. The EABRs and EMLRs were recorded in albino guinea pigs in response to electrical stimulation at the round window, promontory, scala tympani, and modiolus. The EABR and EMLR thresholds were similar. There was no significant difference between thresholds for round-window and scala tympani stimulation. Amplitude/intensity functions for the EMLR differed with site of stimulation. The EMLR seems to be comparable with the EABR for assessing the electrical excitability of the auditory pathway with less electrical artifact contamination. In this respect, round-window and scala tympani stimulation sites are equally efficacious.