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A Circuit for Detection of Interaural Time Differences in the Brain Stem of the Barn Owl

Carr, C. E. and Konishi, M. (1990) A Circuit for Detection of Interaural Time Differences in the Brain Stem of the Barn Owl. Journal of Neuroscience, 10 (10). pp. 3227-3246. ISSN 0270-6474. PMCID PMC6570189. https://resolver.caltech.edu/CaltechAUTHORS:20151202-074927106

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Abstract

Detection of interaural time differences underlies azimuthal sound localization in the barn owl Tyto alba. Axons of the cochlear nucleus magnocellularis, and their targets in the binaural nucleus laminaris, form the circuit responsible for encoding these interaural time differences. The nucleus laminaris receives bilateral inputs from the cochlear nucleus magnocellularis such that axons from the ipsilateral cochlear nucleus enter the nucleus laminaris dorsally, while contralateral axons enter from the ventral side. This interdigitating projection to the nucleus laminaris is tonotopic, and the afferents are both sharply tuned and matched in frequency to the neighboring afferents. Recordings of phase-locked spikes in the afferents show an orderly change in the arrival time of the spikes as a function of distance from the point of their entry into the nucleus laminaris. The same range of conduction time (160 mu sec) was found over the 700-mu m depth of the nucleus laminaris for all frequencies examined (4-7.5 kHz) and corresponds to the range of interaural time differences available to the barn owl. The estimated conduction velocity in the axons is low (3-5 m/sec) and may be regulated by short internodal distances (60 mu m) within the nucleus laminaris. Neurons of the nucleus laminaris have large somata and very short dendrites. These cells are frequency selective and phase-lock to both monaural and binaural stimuli. The arrival time of phase-locked spikes in many of these neurons differs between the ipsilateral and contralateral inputs. When this disparity is nullified by imposition of an appropriate interaural time difference, the neurons respond maximally. The number of spikes elicited in response to a favorable interaural time difference is roughly double that elicited by a monaural stimulus. Spike counts for unfavorable interaural time differences fall well below monaural response levels. These findings indicate that the magnocellular afferents work as delay lines, and the laminaris neurons work as co- incidence detectors. The orderly distribution of conduction times, the predictability of favorable interaural time differences from monaural phase responses, and the pattern of the anatomical projection from the nucleus laminaris to the central nucleus of the inferior colliculus suggest that interaural time differences and their phase equivalents are mapped in each frequency band along the dorsoventral axis of the nucleus laminaris.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1523/JNEUROSCI.10-10-03227.1990DOIArticle
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6570189PubMed CentralArticle
Additional Information:© 1990 by Society for Neuroscience. For the first six months after publication SfN’s license will be exclusive. Beginning six months after publication the Work will be made freely available to the public on SfN’s website to copy, distribute, or display under a Creative Commons Attribution 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/). Received Nov. 3, 1989; revised May 4, 1990; accepted May 9, 1990. We wish to thank Ted Sullivan, Larry Proctor, and Hermann Wagner for helpful discussions and for the computer programs used in this study. We gratefully acknowledge Ad Aertsen, Andy Moiseff, Ed Rubel, Susan Volman, Hermann Wagner, Tom Yin, and two anonymous referees for their thoughtful criticisms of this manuscript. This work was supported by NRSA Grant 07475 to C.E.C. and NIH Grant NS 1461 7 to M.K.
Funders:
Funding AgencyGrant Number
NIH Predoctoral Fellowship07475
NIHNS 14617
Issue or Number:10
PubMed Central ID:PMC6570189
Record Number:CaltechAUTHORS:20151202-074927106
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20151202-074927106
Official Citation:A circuit for detection of interaural time differences in the brain stem of the barn owl. CE Carr, M Konishi. Journal of Neuroscience 1 October 1990, 10 (10) 3227-3246; DOI: 10.1523/JNEUROSCI.10-10-03227.1990
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:62525
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:02 Dec 2015 21:23
Last Modified:30 Oct 2019 17:45

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