An electrophysiological study of neural pathways for corticofugally inhibited neurons in the central nucleus of the inferior colliculus of the big brown bat, Eptesicus fuscus |
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Authors: | Philip H-S Jen Xinde Sun Qi Cai Chen |
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Institution: | (1) Division of Biological Sciences, University of Missouri-Columbia, MO 65211, USA,;(2) Department of Biology, East China Normal University, Shanghai, China,;(3) Department of Biology, Central China Normal University, Wuhan, China, |
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Abstract: | This electrophysiological study tests the hypothesis that one possible neural pathway for corticofugally inhibited neurons
in the central nucleus of the inferior colliculus (ICc) of the big brown bat, Eptesicus fuscus, is mediated through excitatory projections from the auditory cortex (AC) to the external nucleus of the IC (ICx), which
then sends inhibitory inputs to the ICc. This study shows that all neurons in the ICx are broadly tuned to stimulus frequency.
Electrical stimulation in the AC typically increases the number of impulses, expands the auditory spatial response areas,
and broadens the frequency tuning curves (FTCs) of neurons in the ICx. This corticofugal facilitation is mediated at least
in part through NMDA receptors, since application of DL-2-amino-5-phosphonovaleric acid (APV), an antagonist for NMDA, decreases these response properties of neurons in the ICx.
Electrical stimulation in the ICx typically decreases the number of impulses, reduces the auditory spatial response areas,
and narrows the FTCs of neurons in the ICc. This inhibition is mediated at least in part through GABAA receptors, since application of bicuculline, an antagonist for GABA, increases these response properties of neurons in the
ICc. These data suggest that corticofugal facilitation of the ICx and the inhibition of the ICx to the ICc may be one of the
polysynaptic pathways for corticofugal inhibition of neurons in the ICc. Possible functions of this polysynaptic pathway in
acoustic orientation and signal processing are discussed.
Electronic Publication |
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Keywords: | Auditory cortex Corticofugal facilitation Inferior colliculus Intracollicular inhibition Bat |
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