Auditory evoked response in chinchilla: Application to animal audiometry

In chinchilla a neural response to tone pips or the onset of pure tones can be recorded from scalp electrodes. If 64 responses are averaged by a computer the response can be recognized reliably at sound pressure levels at or near chinchilla’s usual behavioral thresholds of hearing. Detection is possible at slightly lower levels if the number of responses is increased to 500 to 1000. The response is an initiallypositive diphasic wave with latency to foot between 1.6 and 4.0 msec. It apparently arises from several structures in the brainstem but chiefly from the inferior colliculus. The technique may be useful in assessing quickly the sensitivity of the peripheral auditory mechanism in small laboratory animals.