Frequency-specific projections of individual neurons in chick brainstem auditory nuclei

Young, Steven R.; Rubel, Edwin W.

doi:10.1523/jneurosci.03-07-01373.1983

Cited by 180 publications

(128 citation statements)

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“…In the chicken, each nucleus magnocellularis axon innervates the ipsilateral nucleus laminaris by dividing into several collaterals of approximately equal length that terminate at different points along the isofrequency band, predominantly in the dorsal neuropil of the nucleus laminaris's monolayer of multipolar neurons. On the contralateral side, the axon runs along the isofrequency band, successively giving off collaterals that terminate predominantly in the ventral neuropil [130]. It has been shown in chicken brain slice preparations, that, as expected from this innervation pattern, action potentials from the ipsilateral side arrive almost simultaneously at all innervated nucleus laminaris neurons, whereas action potentials from the contralateral side are increasingly delayed from caudolateral to rostromedial along the isofrequency band [82].…”

Section: Delay Line-coincidence Detection Circuits In Birdsmentioning

confidence: 92%

“…The axons from the contralateral nucleus magnocellularis form an elongated band of endings along the mediolateral length of the nucleus. These contralateral axons act as delay lines to form a map of ITDs along the mediolateral dimension of nucleus laminaris [82,84,130,131]. Delays are detected by coincidence detection in nucleus laminaris neurons [82,84].…”

Section: Phase-locking Below 2 Khzmentioning

confidence: 99%

“…In birds and mammals, precisely timed spikes encode the timing of acoustic stimuli, and interaural acoustic disparities propagate to binaural processing centers such as the avian nucleus laminaris and the mammalian medial superior olive [20,47,130]. Detection of ITD has been understood on the basis of the Jeffress model [44] in which an array of coincidence detectors receive input from ipsilateral and contralateral excitatory inputs that act as delay lines.…”

Section: Sensitivity To Interaural Time Differencesmentioning

confidence: 99%

“…In birds and mammals, precisely timed spikes encode the timing of acoustic stimuli, and interaural time differences (ITDs) propagate to binaural processing centers such as the avian nucleus laminaris and the mammalian medial superior olive [20,47,130].…”

Section: Introductionmentioning

confidence: 99%

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Coding interaural time differences at low best frequencies in the barn owl

Carr

Köppl

2004

Journal of Physiology-Paris

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In birds and mammals, precisely timed spikes encode the timing of acoustic stimuli, and interaural acoustic disparities propagate to binaural processing centers. The Jeffress model proposes that these projections act as delay lines to innervate an array of coincidence detectors, every element of which has a different relative delay between its ipsilateral and contralateral excitatory inputs. Thus, interaural time difference (ITD) is encoded into the position of the coincidence detector whose delay lines best cancel out the acoustic ITD. Neurons of the avian nucleus laminaris and mammalian MSO phase-lock to both monaural and binaural stimuli but respond maximally when phase-locked spikes from each side arrive simultaneously, i.e. when the difference in the conduction delays compensates for the ITD. McAlpine et al. [Nat. Neurosci. 4 (2001) 396] identified an apparent difference between avian and mammalian ITD coding. In the barn owl, the maximum firing rate appears to encode ITD. This may not be the case for the guinea pig, where the steepest region of the function relating discharge rate to interaural time delay (ITD) is close to midline for all neurons, irrespective of best frequency (BF). These data suggest that low BF ITD sensitivity in the guinea pig is mediated by detection of a change in slope of the ITD function, and not by maximum rate. We review coding of low best frequency ITDs in barn owls and mammals and discuss whether there may be differences in the code used to signal ITD in mammals and birds.

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Section: Delay Line-coincidence Detection Circuits In Birdsmentioning

confidence: 92%

Section: Phase-locking Below 2 Khzmentioning

confidence: 99%

Section: Sensitivity To Interaural Time Differencesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coding interaural time differences at low best frequencies in the barn owl

Carr

Köppl

2004

Journal of Physiology-Paris

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“…A systematic arrangement of axonal projections to an array of neurons was first described anatomically in the chick brain stem by Young and Rubel [2]. When the auditory nerve enters the chick brain stem, it bifurcates, sending one branch to nucleus magnocellularis (NM) and another branch to nucleus angularis (NA).…”

Section: Introductionmentioning

confidence: 99%

The analysis of interaural time differences in the chick brain stem

Hyson

2005

Physiology & Behavior

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The brain stem auditory system of the chick has proven to be a useful model system for analyzing how the brain encodes temporal information. This paper reviews some of the work on a circuit in the brain stem that compares the timing of information coming from the two ears to determine the location of a sound source. The contralateral projection from the cochlear nucleus, nucleus magnocellularis (NM), to nucleus laminaris (NL) forms a delay line as it proceeds from medial to lateral across NL. NL neurons function like coincidence detectors in that they respond maximally when input from the two ears arrive simultaneously. This arrangement may allow NL to code sound space by the relative level of activity across the nucleus. The head anatomy of the chick allows for enhancement of the functional interaural time differences. Comparing the functional interaural time differences to the length of the neural delay line suggests that each NL can encode approximately one hemifield of sound space. Finally it is suggested that inhibitory input into the NM-NL circuit may provide a means to dynamically adjust the gain of the circuit to allow accurate coding of sound location despite changes in overall sound intensity. KeywordsAuditory system; Sound localization; Nucleus magnocellularis; Nucleus laminaris; Coincidence detection; Interaural canal; GABA Temporal information is important in the auditory system both for identification of different sources of sound and for determining the location of sounds. Identification of different sound sources can be accomplished, to a large extent, using monaural cues. While localization of a sound source can also be accomplished, to some extent, with only one ear, significant localization cues are contained in the comparison of binaural information. Sounds located to one side will arrive at the near ear slightly before they arrive at the distant ear and, in general, these offset sounds will be slightly louder in the near ear than in the distant ear. By analyzing differences in the timing and intensity of information at the two ears, the brain can compute the location of a sound source.The circuitry for computing the location of a sound source begins in the brain stem. This report will review some of our work over the past several years on the circuit that begins the neural analysis of interaural time differences in the chick. Emphasis will be given to the anatomical, physiological and neurochemical adaptations in this model system to accomplish binaural sound localization. This manuscript is not meant to be an exhaustive review of the literature in the field, but rather, a story that exemplifies how adaptations at different levels of a system each contribute to enhancing the precision of an important task. Fig. 1A, provides a circuit for transforming time differences at the two ears into a place of maximal activation along an array of neurons. There are two main features of this model: 1) delay lines to an array of neurons and 2) neurons that function as coincidence detectors. As wi...

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Development of the time coding pathways in the auditory brainstem of the barn owl

Carr

Boudreau

1996

J. Comp. Neurol.

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The barn owl's head grows after hatching, causing interaural distances to more than double in the first 3 weeks posthatch. These changes expose the bird to a constantly increasing range of interaural time cues. We have used Golgi and ultrastructural techniques to analyze the development of the connections and cell types of the nucleus magnocellularis (NM) and the nucleus laminaris (NL) with reference to the growth of the head. The time coding circuit is formed but immature at the time of hatching. In the month posthatch, the auditory nerve projection to the NM matures, and appears adult-like by posthatch day (P)21. NM neurons show a late growth of permanent dendrites starting at P6. Over the first month, these dendrites change in length and number, depending upon rostrocaudal position, to establish the adult pattern in which high best frequency neurons have few or no dendrites. These changes are not complete by P21, when NM neurons still have more dendrites than in the adult owl. The neurons of NL have many short dendrites before hatching. Their number is greatly reduced by P6, and then does not change during later development. Like NM neurons, NL neurons and dendrites grow in the first month posthatch, and at P21, NL dendrites are longer than those in the adult owl. Thus, the auditory brainstem circuits grow in the first month after hatching, but are not yet mature at the time the head reaches its adult size.

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Frequency-specific projections of individual neurons in chick brainstem auditory nuclei

Cited by 180 publications

References 22 publications

Coding interaural time differences at low best frequencies in the barn owl

Coding interaural time differences at low best frequencies in the barn owl

The analysis of interaural time differences in the chick brain stem

Development of the time coding pathways in the auditory brainstem of the barn owl

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