Temporal aspects of the effects of cooling on responses of single auditory nerve fibers.
During an investigation of the effects of cochlear cooling on frequency tuning and input/output relations of single auditory nerve fibers in gerbil (Ohlemiller and Siegel (1994) Hear. Res. 80, 174-190), cooling-related changes in post-stimulus time histogram (PSTH) shape and phase-locking to tonebursts were characterized in a small sample of neurons. Local cochlear cooling by 5-10 degrees C below normal core temperature did not alter overall PSTH shape, although some evidence was found for a reduction in the time constants of rapid and short term rate adaptation. The relative contributions of rapid and short term response components appeared unaltered. Effects of cooling on phase-locking were assessed by calculating the synchronization index for responses to intense ( > 70 dB SPL) tonebursts at 0.5, 1.0, and 2.0 kHz. Synchronization filter functions exhibited modest reductions in both magnitude and the upper frequency limit of phase-locking. The effects of cooling on the temporal character of responses appear distinct from those of a simple reduction in stimulus intensity. Results are interpreted in terms of cooling-related changes in responses of cochlear hair cells and afferent neurons, and suggest that temperature artifacts are unlikely to underlie reported species differences in PSTH shape and phase-locking.
Ohlemiller
K K
KK
Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA. kohlemiller@cid.wustl.edu
Siegel
J H
JH
D000161:Acoustic Stimulation; D000818:Animals; D003051:Cochlea / Q000502:physiology*; D003080:Cold Temperature; D005849:Gerbillinae; D009412:Nerve Fibers / Q000502:physiology*; D000159:Vestibulocochlear Nerve / Q000502:physiology*