Neural inhibition sharpens auditory spatial selectivity of bat inferior collicular neurons |
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Authors: | X M Zhou P H-S Jen |
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Institution: | (1) Division of Biological Sciences, University of Missouri-Columbia, MO 65211, USA e-mail: jenp@missouri.edu Tel.: +1-573-882-7479; Fax: +1-573-884-5020, US |
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Abstract: | This study examines the role of neural inhibition in auditory spatial selectivity of inferior collicular neurons of the big
brown bat, Eptesicus fuscus, using a two-tone inhibition paradigm. Two-tone inhibition decreases auditory spatial response areas but increases the slopes
of directional sensitivity curves of inferior collicular neurons. Inferior collicular neurons have either directionally-selective
or hemifield directional sensitivity curves. A directionally-selective curve always has a peak which is at least 50% larger
than the minimum. A hemifield directional sensitivity curve rises from an ipsilateral angle by more than 50% and either reaches
a plateau or declines by less than 50% over a range of contralateral angles. Two-tone inhibition does not change directionally-selective
curves but changes most hemifield directional sensitivity curves into directionally-selective curves. Auditory spatial selectivity
determined both with and without two-tone inhibition increases with increasing best-excitatory frequency. Sharpening of auditory
spatial selectivity by two-tone inhibition is larger for neurons with smaller differences between excitatory and inhibitory
best frequencies. The effect of two-tone inhibition on auditory spatial selectivity increases with increasing inhibitory tone
intensity but decreases with increasing intertone interval. The implications of these findings in bat echolocation are discussed.
Accepted: 18 January 2000 |
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Keywords: | Auditory spatial selectivity Bat Directional slope Inferior colliculus Two-tone inhibition |
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