Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Neural Responses to Overlapping FM Sounds in the Inferior Colliculus of Echolocating Bats

Neural Responses to Overlapping FM Sounds in the Inferior Colliculus of Echolocating Bats Abstract The big brown bat, Eptesicus fuscus, navigates and hunts prey with echolocation, a modality that uses the temporal and spectral differences between vocalizations and echoes from objects to build spatial images. Closely spaced surfaces (“glints”) return overlapping echoes if two echoes return within the integration time of the cochlea (∼300–400 μs). The overlap results in spectral interference that provides information about target structure or texture. Previous studies have shown that two acoustic events separated in time by less than ∼500 μs evoke only a single response from neural elements in the auditory brain stem. How does the auditory system encode multiple echoes in time when only a single response is available? We presented paired FM stimuli with delay separations from 0 to 24 μs to big brown bats and recorded local field potentials (LFPs) and single-unit responses from the inferior colliculus (IC). These stimuli have one or two interference notches positioned in their spectrum as a function of two-glint separation. For the majority of single units, response counts decreased for two-glint separations when the resulting FM signal had a spectral notch positioned at the cell's best frequency (BF). The smallest two-glint separation that reliably evoked a decrease in spike count was 6 μs. In addition, first-spike latency increased for two-glint stimuli with notches positioned nearby BF. The N 4 potential of averaged LFPs showed a decrease in amplitude for two-glint separations that had a spectral notch near the BF of the recording site. Derived LFPs were computed by subtracting a common-mode signal from each LFP evoked by the two-glint FM stimuli. The derived LFP records show clear changes in both the amplitude and latency as a function of two-glint separation. These observations in relation with the single-unit data suggest that both response amplitude and latency can carry information about two-glint separation in the auditory system of E. fuscus. Footnotes Address for reprint requests: M. Sanderson, Box 1953, Dept. of Neuroscience, Brown University, Providence, RI 02912. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2000 The American Physiological Society http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Neurophysiology The American Physiological Society

Neural Responses to Overlapping FM Sounds in the Inferior Colliculus of Echolocating Bats

Journal of Neurophysiology , Volume 83 (4): 1840 – Apr 1, 2000

Loading next page...
 
/lp/the-american-physiological-society/neural-responses-to-overlapping-fm-sounds-in-the-inferior-colliculus-QklooCXPDe

References

References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.

Publisher
The American Physiological Society
Copyright
Copyright © 2011 the American Physiological Society
ISSN
0022-3077
eISSN
1522-1598
Publisher site
See Article on Publisher Site

Abstract

Abstract The big brown bat, Eptesicus fuscus, navigates and hunts prey with echolocation, a modality that uses the temporal and spectral differences between vocalizations and echoes from objects to build spatial images. Closely spaced surfaces (“glints”) return overlapping echoes if two echoes return within the integration time of the cochlea (∼300–400 μs). The overlap results in spectral interference that provides information about target structure or texture. Previous studies have shown that two acoustic events separated in time by less than ∼500 μs evoke only a single response from neural elements in the auditory brain stem. How does the auditory system encode multiple echoes in time when only a single response is available? We presented paired FM stimuli with delay separations from 0 to 24 μs to big brown bats and recorded local field potentials (LFPs) and single-unit responses from the inferior colliculus (IC). These stimuli have one or two interference notches positioned in their spectrum as a function of two-glint separation. For the majority of single units, response counts decreased for two-glint separations when the resulting FM signal had a spectral notch positioned at the cell's best frequency (BF). The smallest two-glint separation that reliably evoked a decrease in spike count was 6 μs. In addition, first-spike latency increased for two-glint stimuli with notches positioned nearby BF. The N 4 potential of averaged LFPs showed a decrease in amplitude for two-glint separations that had a spectral notch near the BF of the recording site. Derived LFPs were computed by subtracting a common-mode signal from each LFP evoked by the two-glint FM stimuli. The derived LFP records show clear changes in both the amplitude and latency as a function of two-glint separation. These observations in relation with the single-unit data suggest that both response amplitude and latency can carry information about two-glint separation in the auditory system of E. fuscus. Footnotes Address for reprint requests: M. Sanderson, Box 1953, Dept. of Neuroscience, Brown University, Providence, RI 02912. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “ advertisement ” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Copyright © 2000 The American Physiological Society

Journal

Journal of NeurophysiologyThe American Physiological Society

Published: Apr 1, 2000

There are no references for this article.