TEMPORAL ASPECTS OF THE EFFECTS OF COOLING ON RESPONSES OF SINGLE AUDITORY-NERVE FIBERS

During an investigation of the effects of cochlear cooling on frequenc y 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 phas e-locking to tonebursts were characterized in a small sample of neuron s. Local cochlear cooling by 5-10 degrees C below normal core temperat ure did not alter overall PSTH shape, although some evidence was found for a reduction in the time constants of rapid and short term rate ad aptation. The relative contributions of rapid and short term response components appeared unaltered. Effects of cooling on phase-locking wer e assessed by calculating the synchronization index for responses to i ntense ( > 70 dB SPL) tonebursts at 0.5, 1.0, and 2.0 kHz. Synchroniza tion filter functions exhibited modest reductions in both magnitude an d the upper frequency limit of phase-locking. The effects of cooling o n the temporal character of responses appear distinct from those of a simple reduction in stimulus intensity. Results are interpreted in ter ms 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-locki ng. (C) 1998 Elsevier Science B.V. All rights reserved.