Bradford J. May
Shelly J. McQuone
Dept. of Otolaryngol.---HNS, The Johns Hopkins Univ. School of Med., 720 Rutland Ave., Baltimore, MD 21205
The effects of olivocochlear efferent lesions on intensity discrimination
were examined in five cats. Cats were trained with food reinforcement to signal
the detection of a change in the intensity of a pure tone by releasing a
response lever. Intensity cues were conveyed by 1- and 8-kHz tone bursts in
quiet and in the presence of continuous broadband noise. After the collection
of baseline behavioral data, the olivocochlear bundle (OCB) was sectioned with
bilateral knife cuts on the floor of the IVth ventricle. The completeness of
OCB lesions was evaluated with cochlear acetylcholinesterase staining
procedures. Although intensity discrimination was not negatively affected by
OCB lesions when tests were conducted in quiet, performance deficits were noted
when intensity discrimination was measured in the presence of noise. These data
suggest that olivocochlear feedback may play an important role in the auditory
processing of acoustic signals in noise backgrounds. Behavioral results will be
discussed in terms of electrophysiological measures of intensity encoding.
[Work supported by NIDCD Grant No. DC00979 and the W. M. Keck Foundation.]