Effects of acute noise traumata on whole-nerve and single-unit activity.

This paper gives some preliminary results of a research program on the effects of noise traumata on cochlear functioning. Measurements reported here include: the latency of the whole-nerve (compound) action potential (AP), the selectivity of frequency-tuning curves (e.g., the Q10-values) measured for the AP (with a forward-masking technique) and for single units in the antero-ventral cochlear nucleus (AVCN), the degree of phase-locking of the action potentials of these units to the stimulus waveform, and the phase of the stimulus waveform to which these potentials are locking. The noise traumata were induced during the experiments. After inducement of the traumata we found: an increase of AP latency, if a sinusoidal stimulas was presented at the same sound pressure level as before the trauma; no effect on AP latency (for most stimulus frequencies), if the latency values measured at the pre- and post-trauma thresholds were compared; a decrease of Q10-values of the AP frequency-tuning curves, (the pre-trauma Q10-values were small in comparison with single nerve fiber data); a decrease of the Q10-values of the single-unit frequency-tuning curves; no effect on the degree of phase-locking of the single-unit potentials to the stimulus waveform; an increase of cochlear response time calculated from the phase of the stimulus waveform to which the single-unit potentials are locking as a function of stimulus frequency.