Threshold sensitivity and frequency selectivity measured with round window whole nerve action potentials in the awake, restrained chinchilla.

Chronic electrodes, placed on the round windows of four adult chinchillas, were used to measure whole-nerve action potential (AP) thresholds and tuning curves. The AP quiet thresholds were within 17 dB of thresholds measured by behavioral methods and within 3 dB of those measured by other evoked response procedures. The AP tuning curves, obtained by a simultaneous masking procedure, were also similar to previously measured tuning curves in the chinchilla. These results indicate that long-term indwelling electrodes can be successfully placed on the chinchilla round window and used to measure threshold sensitivity and frequency selectivity. Recordings from these electrodes could be used in a variety of situations and may be particularly useful in studying the effects of noise on the cochlea.