Affiliations: Department of Surgery, Division of Otolaryngology, School of Medicine, UMC, Columbia, Missouri, USA
Note: [1] Portions of these data were presented at the annual meeting of the American Society for Gravitational and Space Biology, October 20–23, 1993, Arlington, Virginia.
Note: [*] Reprint address: Dr. Sherri M. Jones, Dept. of Surgery, Division of Otolaryngology, 207 Allton Building, DC 375.00, School of Medicine, UMC, Columbia MO 65212 USA; Tel: (573) 884-6278; Fax: (573) 884-4278.
Abstract: Electrophysiological responses to pulsed linear acceleration stimuli were recorded in chicken embryos incubated for 19 or 20 days (E19/E20). Responses occurred within the first 16 ms following the stimulus onset. The evoked potentials disappeared following bilateral labyrinthectomy, but persisted following cochlear destruction alone, thus demonstrating that the responses were vestibular. Approximately 8 to 10 response peaks could be identified. The first 4 positive and corresponding negative components (early peaks with latencies < 6.0 ms) were scored and latencies and amplitudes quantified. Vestibular response latencies were significantly longer (P < 0.01) and amplitudes significantly smaller (P < 0.001) than those observed in 2-week-old birds. Mean response threshold for anesthetized embryos was −15.9dBre 1.0 g/ms, which was significantly higher (P < 0.03) than those observed in 2-week-old birds (−23.0dBre 1.0 g/ms). Latency/intensity functions (that is, slopes) were not significantly different between embryos and 2-week-old animals, but amplitude/intensity functions for embryos were significantly shallower than those for 2-week-old birds (P < 0.001). We presume that these differences reflect the refinement of sensory function that occurs following 19 to 20 days of incubation. The recording of vestibular evoked potentials provides an objective, direct and noninvasive measure of peripheral vestibular function in the embryo and, as such, the method shows promise as an investigative tool. The results of the present study form the definitive basis for using vestibular evoked potentials in the detailed study of avian vestibular ontogeny and factors that may influence it.
Keywords: vestibular ontogeny, vestibular evoked potentials, linear acceleration, birds, linear jerk
