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Biophysical basis of the sound analog membrane potential that underlies coincidence detection in the barn owl

Ashida, Go and Funabiki, Kazuo and Carr, Catherine E. (2013) Biophysical basis of the sound analog membrane potential that underlies coincidence detection in the barn owl. Frontiers in Computational Neuroscience, 7 . Art. No. 102. ISSN 1662-5188. doi:10.3389/fncom.2013.00102.

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Interaural time difference (ITD), or the difference in timing of a sound wave arriving at the two ears, is a fundamental cue for sound localization. A wide variety of animals have specialized neural circuits dedicated to the computation of ITDs. In the avian auditory brainstem, ITDs are encoded as the spike rates in the coincidence detector neurons of the nucleus laminaris (NL). NL neurons compare the binaural phase-locked inputs from the axons of ipsi- and contralateral nucleus magnocellularis (NM) neurons. Intracellular recordings from the barn owl's NL in vivo showed that tonal stimuli induce oscillations in the membrane potential. Since this oscillatory potential resembled the stimulus sound waveform, it was named the sound analog potential (Funabiki et al., 2011). Previous modeling studies suggested that a convergence of phase-locked spikes from NM leads to an oscillatory membrane potential in NL, but how presynaptic, synaptic, and postsynaptic factors affect the formation of the sound analog potential remains to be investigated. In the accompanying paper, we derive analytical relations between these parameters and the signal and noise components of the oscillation. In this paper, we focus on the effects of the number of presynaptic NM fibers, the mean firing rate of these fibers, their average degree of phase-locking, and the synaptic time scale. Theoretical analyses and numerical simulations show that, provided the total synaptic input is kept constant, changes in the number and spike rate of NM fibers alter the ITD-independent noise whereas the degree of phase-locking is linearly converted to the ITD-dependent signal component of the sound analog potential. The synaptic time constant affects the signal more prominently than the noise, making faster synaptic input more suitable for effective ITD computation.

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Additional Information:© 2013 Ashida, Funabiki and Carr. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. Received: 04 December 2012; Accepted: 07 July 2013; Published online: 08 November 2013. We thank Masakazu Konishi and Kousuke Abe for valuable comments and discussion. This work was supported by NIH DC00436 to Catherine E. Carr, by NIH P30 DC04664 to the University of Maryland Center for the Comparative and Evolutionary Biology of Hearing, by fellowships from the Alexander von Humboldt Foundation and the Hanse-Wissenschaftskolleg to Go Ashida and Catherine E. Carr, and by a postdoctoral fellowship from JSPS and Grant-in-Aid for Scientific Research (B) to Kazuo Funabiki. Go Ashida is also supported by the Cluster of Excellence “Hearing4all” at the University of Oldenburg.
Funding AgencyGrant Number
NIHP30 DC04664
Alexander von Humboldt FoundationUNSPECIFIED
Japan Society for the Promotion of Science (JSPS)UNSPECIFIED
University of Oldenburg Cluster of Excellence “Hearing4all”UNSPECIFIED
Subject Keywords:phase-locking, sound localization, auditory brainstem, periodic signals, oscillation, owl
Record Number:CaltechAUTHORS:20140103-111302927
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Official Citation:Ashida G, Funabiki K and Carr CE (2013) Biophysical basis of the sound analog membrane potential that underlies coincidence detection in the barn owl. Front. Comput. Neurosci. 7:102. doi: 10.3389/fncom.2013.00102
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43203
Deposited By: Tony Diaz
Deposited On:03 Jan 2014 21:52
Last Modified:10 Nov 2021 16:34

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