Embryogenesis of arborization pattern and topography of individual axons in N. Laminaris of the chicken brain stem

Young, Steven R.; Rubel, Edwin W.

doi:10.1002/cne.902540402

Cited by 118 publications

(99 citation statements)

References 95 publications

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“…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%

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: Phase-locking Below 2 Khzmentioning

confidence: 99%

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

Carr

Köppl

2004

Journal of Physiology-Paris

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“…All nuclei are tonotopically organized, with high best frequencies rostromedial and low best frequencies caudolateral in NM and NL Parks, 1975, 1988;Warchol and Dallos, 1990). NL receives projections from NM such that ipsilateral axons project to NL dorsal dendrites and contralateral axons to the ventral dendrites Young and Rubel, 1986). Scale bar = 500 μm.…”

Section: Possible Subunit Components In Nmdar In Chick Cochlear Nucleimentioning

confidence: 99%

“…NM neurons encode the timing of the auditory stimulus in a pathway that contributes to sound localization based on interaural timing differences (Overholt et al, 1992;Kuba et al, 2002), whereas NA encodes other auditory cues Fukui and Ohmori, 2003;MacLeod and Carr, 2005). NL receives projections from NM such that ipsilateral axons project to NL dorsal dendrites and contralateral axons to the ventral dendrites Young and Rubel, 1986).The general expression patterns of NMDAR mRNAs were compared in NM, NL, and NA at four ages: E10, E14, P0, and adult (Figs. 2, 3, 6, 7).…”

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“…E14 is also when responses to loud environmental sound signals may be recorded in the cochlear nuclei (Saunders et al, 1973;Jackson and Rubel, 1978). The refinement of the axonal synaptic connections from NM to NL takes place between E14 and E16, when both the dorsal and the ventral terminal fields of NM axons form narrow bands across NL (Smith, 1981;Young and Rubel, 1986;Parks et al, 1987). Synaptophysin and syntaxin immunoreactivity also increase in NM and NL between E12 and E16 (Alladi et al., 2002).…”

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Development of NMDA R1 expression in chicken auditory brainstem

Tang

Carr

2004

Hearing Research

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N-methyl-D-aspartate (NMDA) receptor subunit-specific probes were used to characterize developmental changes in the distribution of excitatory amino acid receptors in the chicken's auditory brainstem nuclei. Although NR1 subunit expression does not change greatly during the development of the cochlear nuclei in the chicken Hear. , there are significant developmental changes in NR2 subunit expression. We used in situ hybridization against NR1, NR2A, NR2B, NR2C, and NR2D to compare NR1 and NR2 expression during development. All five NMDA subunits were expressed in the auditory brainstem before embryonic day (E) 10, when electrical activity and synaptic responses appear in the nucleus magnocellularis (NM) and the nucleus laminaris (NL). At this time, the dominant form of the receptor appeared to contain NR1 and NR2B. NR2A appeared to replace NR2B by E14, a time that coincides with synaptic refinement and evoked auditory responses. NR2C did not change greatly during auditory development, whereas NR2D increased from E10 and remained at fairly high levels into adulthood. Thus changes in NMDA NR2 receptor subunits may contribute to the development of auditory brainstem responses in the chick. Indexing termscochlear nucleus; magnocellularis; laminaris; angularis; tonotopic gradient Physiological studies have shown that the auditory system is characterized by fast, accurate encoding of auditory information (Warchol and Dallos, 1990; Zhang and Trussell, 1994a,b;Fukui and Ohmori, 2003). We have therefore investigated the distribution of subtypes of Nmethyl-D-aspartate (NMDA) receptors (NMDAR) in the brainstem auditory nuclei of the chicken to determine whether changes in receptors may reflect the development of specializations for temporal processing. NMDAR can contain two classes of subunits, NR1 and NR2 (A-D). The third class of subunits (NR3), containing NR3A and NR3B, is thought to act as modulators of the NMDAR (Ciabarra et al., 1995;Nishi et al., 2001; for review see Cull-Candy, 2001). A functional NMDAR appears to consist of two NR1 subunits and two or three NR2 subunits. NR1 is the fundamental subunit necessary for the NMDAR complex, and its expression is spatiotemporally ubiquitous compared with that of NR2 subunits in vertebrate brain (Watanabe et al., 1992;Wada et al., 2004).Changes in NMDAR composition characterize the development of forebrain circuits. NR2B has been shown to be necessary for synapse formation and plasticity (Tang et al., 1999;Slutsky et al., 2004), whereas NR2A expression is associated with synaptic maturation (Fu et al., 2005). NMDAR made up of NR2B and NR1 subunits are the dominant form during NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript the "critical period" window for plasticity in mouse visual cortex (Quinlan et al., 1999a) and barrel cortex ) and in vocal learning regions of songbirds (Basham et al., 1999;Singh et al., 2000;Ding and Perkel, 2004). Near the end of the critical period, there is a gradual increase in the contribution of NR2A subunits i...

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“…ITDs are detected by a neuronal circuit consisting of axons from NM, serving as delay lines, and neurons of the nucleus laminaris (NL), serving as coincidence detectors (Sullivan and Konishi, 1984b;Young and Rubel, 1986;Carr and Konishi, 1990;Overholt et al, 1992;Carr, 1993;Joseph and Hyson, 1993). NL is thought to be homologous or similar to the medial superior olivary nucleus of mammals (MSO).…”

Section: Abstract: Owl; Sound Localization; Nucleus Laminaris; Intermentioning

confidence: 99%

Effects of Interaural Intensity Difference on the Processing of Interaural Time Difference in the Owl’s Nucleus Laminaris

1997

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Interaural time and intensity differences (ITD and IID) are processed independently in the owl's auditory system. This paper examines whether this independence is established in nucleus laminaris (NL), the first site of ITD processing. A plot of discharge rate against time difference (ITD curve) is sinusoidal in NL. The ITDs that produce the peaks are called the most favorable ITDs, and those that produce the troughs are called the least favorable ITDs. IID had little effect on the discharge rates of laminaris neurons for the most and least favorable ITDs. The degree of peak-trough modulation changed slightly with variation in IID. In contrast, IID in tonal stimuli affected the temporal aspect of ITD curves depending on the difference between the stimulus frequency and the neuron's best frequency (BF). For frequencies below BF, IID caused large and systematic shifts in ITD toward the ear in which the sound was louder, whereas for frequencies above BF, IID caused small shifts in ITD toward the opposite ear. IID had little effect on ITD curves taken with BF or broadband noise. These results can be largely accounted for by the effects of frequency and intensity on the timing of impulses at the level of the cochlear nuclei. Thus, the processing of ITD by NL neurons is independent of IID for behaviorally relevant stimuli, because the timing of impulses is insensitive to sound level when the signal is broadband. Key words: owl; sound localization; nucleus laminaris; interaural time difference; interaural intensity difference; parallel pathwaysParallel processing of information is an important operation in many sensory systems (see, for example, owl's auditory system: Takahashi et al., 1984; monkey visual system: Maunsell et al., 1990;Merigan and Maunsell, 1993; fish electrosensory system: Heiligenberg, 1991). The barn owl's auditory brainstem offers a relatively simple system in which to analyze the relationship between parallel pathways. The owl uses interaural time and intensity differences (ITD and IID) for sound localization (Moiseff, 1989b). The independence of these cues is important for the species, because they code for different spatial coordinate axes, ITD mainly for azimuth and IID mainly for elevation. ITD and IID are processed in separate parallel pathways that start at the level of the cochlear nucleus. The avian auditory system has two anatomically and physiologically distinct cochlear nuclei, nucleus magnocellularis (NM) and nucleus angularis (NA). NM neurons lack dendrites and contain end bulbs of Held, whereas NA neurons have dendrites and bouton-type synapses (Parks, 1981;Jhaveri and Morest, 1982;Takahashi and Konishi, 1988a;Carr and Boudreau, 1993). NM neurons show phase locking, whereas NA neurons do not except for very low frequencies (Sachs and Sinnott, 1978;Sullivan and Konishi, 1984a;Konishi et al., 1985;Warchol and Dallos, 1990). The time-and intensity-processing pathways converge in the inferior colliculus, where neurons selective for combinations of ITD and IID are found. Partial inactivat...

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Embryogenesis of arborization pattern and topography of individual axons in N. Laminaris of the chicken brain stem

Cited by 118 publications

References 95 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

Development of NMDA R1 expression in chicken auditory brainstem

Effects of Interaural Intensity Difference on the Processing of Interaural Time Difference in the Owl’s Nucleus Laminaris

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