The Journal of Neuroscience, May 15, 1998, 18(10):3955-3966
Response Classes in the Dorsal Cochlear Nucleus and Its Output
Tract in the Chloralose-Anesthetized Cat
Philip X.
Joris
Department of Neurophysiology, University of Wisconsin-Madison,
Madison, Wisconsin 53706, and Coleman and Epstein Laboratories,
Department of Otolaryngology, University of California at San
Francisco, San Francisco, California 94143-0526
Neurons in the dorsal cochlear nucleus (DCN) can be classified into
three major physiological classes on the basis of responses to pure
tone and broadband noise stimuli. A circuit diagram that associates
these classes with different cell types has been proposed. According to
this proposal, type II cells are inhibitory interneurons that respond
well to tones and poorly to broadband noise, type IV cells are
projection neurons with the opposite behavior, and type III cells are
an inhomogeneous class with intermediate properties. To test the
associations proposed, I compared the response type distribution in the
DCN with its output tract, the dorsal acoustic stria (DAS), in
chloralose-anesthetized cats.
Axonal recordings in the DAS showed type III and IV responses as in
DCN, but no type II responses. Compared with reports in decerebrate
animals, fewer type IV neurons were encountered having sustained
inhibition that generated strongly nonmonotonic responses to tones in
both DCN and DAS. The presence of type II responses in the nucleus, but
not in the output tract, offers strong support for the proposed
association with DCN interneurons. On the other hand, the distinction
between type III and IV responses needs refinement because the
differences are only graded and because both types of responses occur
in DAS, which shows that they are both associated with projection
neurons.
Key words:
audition; dorsal cochlear nucleus; dorsal
acoustic stria; chloralose; response type; cat
Copyright © 1998 Society for Neuroscience 0270-6474/98/18103955-12$05.00/0
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