Sharpening of frequency tuning by inhibition in the thalamic auditory
nucleus of the mustached bat.
Nobuo Suga, Yunfeng Zhang and Jun Yan.
Department of Biology, Washington University, One Brookings Drive, St.
Louis, MO 63130, U.S.A..
APStracts 4:0003N, 1997.
ABSTRACT
(1) Unlike quasi-triangular frequency-tuning curves of peripheral neurons,
pencil- or spindle-shaped frequency-tuning curves have been found in the
central auditory systems of many species of animals belonging to different
classes. Inhibitory tuning curves (areas) are commonly found on both sides of
such "level-tolerant" sharp frequency-tuning curves (excitatory areas).
However, it has not yet been examined whether sharpening of frequency tuning
takes place in the MGB. One of the aims of the present research is to examine
whether frequency tuning is sharpened by inhibition in the MGB and whether
this sharpening, if any, occurs in addition to that performed in prethalamic
auditory nuclei. We injected an inhibitory transmitter antagonist, bicuculline
methiodide (BMI), into the MGB of the mustached bat and studied its effect on
frequency-tuning curves and auditory responses of single "DSCF" neurons in the
MGB. DSCF neurons are those which are particularly suited for processing a
Doppler-shifted constant-frequency (DSCF) component of biosonar signals at
61 kHz. Cortical DSCF neurons were recently found to show facilitative
responses to paired sounds. That is, they are combination-sensitive. The other
aim of the present research is to examine whether thalamic DSCF neurons are
also combination-sensitive.
Received 26 December 1995; accepted in final form 18 December 1996.
APS Manuscript Number J864-5.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 21 January 1997