Here, we describe a sound-intensity-dependent mechanism for compensating for the small ITD cues in the coincidence detector neurons in the Nucleus laminaris (NL) of the chicken aged from 3 to 29 d after hatching. 
ITD is initially computed by circuits consisting of axonal delay lines from one of the cochlear nuclei and coincidence detector neurons in the Nucleus laminaris (NL).
In the avian brainstem, nucleus magnocellularis (NM) projects bilaterally to Nucleus laminaris (NL) in a pathway that facilitates sound localization.
We show here that, like in the barn owl, the brainstem Nucleus laminaris in mature chickens displayed the major features of a place code of ITD.
Differential innervation of segregated dendritic domains in the chick Nucleus laminaris (NL), composed of third-order auditory neurons, provides a unique model to study synaptic regulation of dendritic structure.
We investigated early development of neuronal properties of chicken Nucleus laminaris neurons, the third-order auditory neurons critically involved in sound localization.
Mid-line injections resulted in stable labelling of neurons of the nucleus magnocellularis (NM), whereas injections into the SON retrogradely labelled neurons of the Nucleus laminaris (NL).
In the barn owl, maps of interaural time difference (ITD) are created in the Nucleus laminaris (NL) by interdigitating axons that act as delay lines.
Several nuclei of the ascending auditory pathway showed a moderate to high density of GABAergic neurons including the cochlear nuclei, Nucleus laminaris, superior olivary nucleus, mesencephalic nucleus lateralis pars dorsalis, and nucleus ovoidalis.
In particular the neurons optimized for linear summation electrotonically separated their synapses, as found in avian Nucleus laminaris neurons, and neurons optimized for spike-order detection had primary dendrites of significantly different diameter, as found in the basal and apical dendrites of cortical pyramidal neurons.
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).
Primary cultures of neurons from nucleus magnocellularis and Nucleus laminaris were prepared from embryonic day 6.5 chicken.
In Nucleus laminaris of birds, neurons behave as coincidence detectors for sound source localization and encode interaural time differences (ITDs) separately at each characteristic frequency (CF). Here we show, in Nucleus laminaris of the chick, that the site of spike initiation in the axon is arranged at a distance from the soma, so as to achieve the highest ITD sensitivity at each CF.
Neurons of the avian Nucleus laminaris (NL) compute the interaural time difference (ITD) by detecting coincident arrivals of binaural signals with submillisecond accuracy.
In the avian auditory system, the neural network for computing the localization of sound in space begins with bilateral innervation of Nucleus laminaris (NL) by nucleus magnocellularis (NM) neurons.
In the medulla of 7- and 8-day embryos, we identified four response areas, corresponding to ipsilateral Nucleus magnocellularis (NM) and Nucleus angularis (NA), which receive the auditory afferents, and ipsi- and contralateral Nucleus laminaris (NL), which receive projections from NM.
The actual locus of the computation of the ITD is before ICcc in the Nucleus laminaris (NL), and ICcc receives no inputs carrying information that did not originate in NL.
In Nucleus laminaris, by this time, while abundant Kv3.1b occurs in the perinuclear cytoplasm, a translocation to the cell membrane domain has not yet occurred, and the mature peri-synaptic localization is delayed to a later stage.
For these experiments, we used single-cell electroporation, live cell imaging, in vitro deafferentation, pharmacology, and electrophysiological stimulation to study how local alterations in synaptic input affect dendritic branch structure in Nucleus laminaris (NL).
Interaural timing differences (ITDs) are computed using axonal delay lines and cellular coincidence detectors in Nucleus laminaris (NL).
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.
Coincidence detection of bilateral acoustic signals in Nucleus laminaris (NL) is the first step in azimuthal sound source localization in birds.
Nucleus magnocellularis (NM), nucleus angularis (NA), and Nucleus laminaris (NL), second- and third-order auditory neurons in the avian brainstem, receive GABAergic input primarily from the superior olivary nucleus (SON).
Previously we reported morphological effects of prenatal auditory stimulation by species-specific and sitar musical sounds on the chick brainstem auditory nuclei-nucleus magnocellularis and Nucleus laminaris.
To shed new light on the basic mechanism underlying this precise temporal neuronal coding, we analyzed the neurophonic potential, a characteristic multiunit response, in the barn owl's Nucleus laminaris.
The avian auditory brain stem consists of a network of specialized nuclei, including Nucleus laminaris (NL) and superior olivary nucleus (SON).
The interaural time difference (ITD) is a cue for localizing a sound source along the horizontal plane and is first determined in the Nucleus laminaris (NL) in birds.
One possible exception to this parallel organization is the inhibitory input provided by the superior olivary nucleus (SON) to nucleus angularis (NA), nucleus magnocellularis (NM), and Nucleus laminaris (NL) and contralateral SON (SONc).
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.
To understand the cellular mechanism of response to prenatal auditory stimulation, we studied the expression of c-Fos and c-Jun in brainstem auditory nuclei, nucleus magnocellularis, and Nucleus laminaris of the domestic chick.
NM in turn innervates Nucleus laminaris (NL) bilaterally.
NR1-ir first appeared in the nucleus magnocellularis (NM) and Nucleus laminaris (NL) at E10.
Specificity is exemplified at cellular and subcellular levels in the chick auditory brainstem, where nucleus magnocellularis (NM) neurons project bilaterally to Nucleus laminaris (NL).
A biologically detailed model of the binaural avian Nucleus laminaris is constructed, as a two-dimensional array of multicompartment, conductance-based neurons, along tonotopic and interaural time delay (ITD) axes. The model is based primarily on data from chick Nucleus laminaris.
In birds, ITDs are first encoded in neurons of the Nucleus laminaris (NL) through the precise coincidence of binaural synaptic inputs.
KCNC1b specific staining has a late onset with immunostaining first appearing in the regions that map high frequencies in nucleus magnocellularis (NM) and Nucleus laminaris (NL).
Here we have examined a specific case of how synaptic plasticity can affect temporal coincidence detection, by experimentally characterizing synaptic depression at the synapse between neurons in the nucleus magnocellularis and coincidence detection neurons in the Nucleus laminaris in the chick auditory brainstem. We combine an empirical description of this depression with a biophysical model of signalling in the Nucleus laminaris. This mechanism may help Nucleus laminaris neurons to pass specific sound localization information to higher processing centres..
We have determined the consequence of increased auditory stimulation on the developmental profile of synaptic proteins, synaptophysin and syntaxin 1, in the chick brainstem auditory nuclei, nucleus magnocellularis and Nucleus laminaris, by immunohistochemistry and western blotting techniques. During normal synaptogenesis of nucleus magnocellularis and Nucleus laminaris, synaptophysin immunoreactivity increased significantly from E8 to E20, in parallel with synapse formation, and reduced at hatching.
Nucleus magnocellularis (NM) in the avian auditory brainstem receives auditory input from nerve the VIIIth and projects bilaterally to Nucleus laminaris (NL).
They compute ITDs in a circuit in Nucleus laminaris (NL) that is reorganized with respect to birds like the chicken.
The Nucleus laminaris is the first site that detects ITDs by methods of delay lines and coincidence detection. The present paper reports the results of manipulating inhibition in the Nucleus laminaris and its effects on the optic tectum neurons. Injection of GABA or muscimol (a GABA(A) receptor agonist) in the Nucleus laminaris reduces the responses of its neurons to ITD. This finding proves that GABA(A) receptor-mediated inhibition acts on the Nucleus laminaris neurons.
Coincidence detection at the Nucleus laminaris (NL) of a chicken was improved between embryos (embryonic days (E) 16 and 17) and chicks (post-hatch days (P) 2-7) in slice preparations.
In this study, we examined cell number and size, and volume of auditory nuclei, specifically in nucleus magnocellularis and Nucleus laminaris in Belgian Waterslager canaries.
Neurons in the Nucleus laminaris detect the coincidence of binaural signals, and are the first neurons to calculate the interaural time difference for the sound source localization in birds. In this paper, we have studied contributions of synaptic depression to the coincidence detection in the Nucleus laminaris in a slice preparation of the chick embryo (E16-18), using the whole-cell patch recording technique.
The nucleus centralis of the torus semicircularis receives few 5-HT-, TH-, substance P-, and menkephalin-immunoreactive fibres and terminals, in marked contrast to the external Nucleus laminaris of the torus semicircularis, in which 5-HT-, TH-, substance P-, and menkephalin-immunoreactive elements and cell bodies show a laminar distribution.
Several brainstem regions, including nucleus rotundus, the medial spiriform nucleus (SpM), the principle nucleus of the trigeminal nerve, Nucleus laminaris and scattered cell groups throughout the isthmus and pontine reticular formation stain intensely for iron.
The owl's Nucleus laminaris contains coincidence detector neurons that receive input from the left and right cochlear nuclei. Monaural frequency-tuning curves of Nucleus laminaris neurons showed small interaural differences.
In both barn owls and chickens, Kv3.1 mRNA was expressed in the cochlear nucleus magnocellularis (NM) and the Nucleus laminaris (NL).
In the avian auditory brainstem, nucleus magnocellularis (NM) functions to relay phase-locked signals to Nucleus laminaris for binaural coincidence detection. The results lead us to propose that GABAergic inhibition enhances phase-locking fidelity of NM neurons, which is essential to binaural coincidence detection in Nucleus laminaris..
The avian auditory brainstem nuclei nucleus magnocellularis (NM) and Nucleus laminaris (NL) display highly precise patterns of neuronal connectivity.
NM in turn projects tonotopically to Nucleus laminaris (NL), maintaining binaural specificity with projections to either dorsal or ventral NL dendrites.
The results indicate that the AMPA receptors of the cochlear ganglion, nucleus magnocellularis and Nucleus laminaris share a number of structural and functional properties that distinguish them from the AMPA receptors of brainstem motor neurons, namely a lower relative abundance of glutamate receptor (GluR)2 transcript and much lower levels of GluR2 immunoreactivity, higher relative levels of GluR3 flop and GluR4 flop, lower relative abundance of the C-terminal splice variants GluR4c and 4d, less R/G editing of GluR2 and 3, greater permeability to calcium, predominantly inwardly rectifying I-V relationships, and greater susceptibility to block by Joro spider toxin.
In the hindbrain, CR-IR was first observed in the rostromedial regions of the cochlear nucleus magnocellularis and the Nucleus laminaris, and in the dorsal regions of the nucleus angularis and in the nucleus of the lateral lemniscus.
During early brainstem development, trkB and trkC are localized in the neuronal cell bodies and in the surrounding neuropil of nucleus magnocellularis (NM) and Nucleus laminaris (NL).
Located in the ventrolateral region of the avian brainstem, the superior olivary nucleus (SON) receives inputs from nucleus angularis (NA) and Nucleus laminaris (NL) and projects back to NA, NL, and nucleus magnocellularis (NM).
Neurons in the avian Nucleus laminaris (NL) are the first to receive binaural information and are presumed to play a role in encoding interaural time differences (ITD).
In the Nucleus laminaris we observed a characteristic palisade of non-ependymal glia, reactive to GFAP but not to vimentin, which almost completely disappears by adulthood.
Synaptic inputs to Nucleus laminaris (NL) neurones were studied in a brainstem slice preparation of chick embryos (E15-20) using the whole-cell patch clamp technique.
In the Nucleus laminaris and in the superior olive, GluR2/3 and GluR4 immunoreactivity reached adult-like patterns by 3 weeks after hatching.
The Nucleus laminaris (NL) undergoes programmed developmental cell death of 19% between embryonic day 9 (E9) and E17.
Neurons in nucleus magnocellularis (NM) and Nucleus laminaris (NL) of the chick brainstem auditory system show an unusual physiological response to GABA.
In the Nucleus laminaris (NL), development of normal dendritic size is dependent on a normal inner ear, but most of the highly specialized dendritic organization of this nucleus, which is important for low-frequency sound localization, can develop normally in the absence of cochlear influences.
This paper examines whether this independence is established in Nucleus laminaris (NL), the first site of ITD processing.
The cytology of the nucleus magnocellularis and the Nucleus laminaris in the barn owl, as well as the axonal pathways connecting them, were studied. In the Nucleus laminaris, two cell types were characterized as distinct to the low-frequency region: stellate neurons with long, smooth dendrites, and multipolar neurons with thick, spiny dendrites. The low-frequency projections from the nucleus magnocellularis showed two terminal fields in the Nucleus laminaris: one containing a rough tonotopic representation and a second one where all low-frequency projections converged.
In the auditory brainstem, levels of GluR2/3 and GluR4 were very high in the cochlear nucleus magnocellularis and the Nucleus laminaris.
DYN-I was found in a few small cells in the Nucleus laminaris (NL) and in the superior olive (SO).
Neurons of the owl's Nucleus laminaris serve as coincidence detectors for measurement of interaural time difference. The discharge rate of Nucleus laminaris neurons for both monaural and binaural stimulation increased with sound intensity until they reached an asymptote. Intense sounds affected neither the ratio between binaural and monaural responses nor the interaural time difference for which Nucleus laminaris neurons were selective. We hypothesize that inhibitory input whose strength increases with sound intensity protects Nucleus laminaris neurons from losing their sensitivity to interaural time difference with intense sounds..
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.
Neurons of the avian Nucleus laminaris (NL) provide a neural substrate for azimuthal sound localization.
Neurons in nucleus magnocellularis (NM) and Nucleus laminaris (NL), second and third order auditory nuclei, discharge spontaneously in synchronous bursts at periodic intervals.
Recordings were made in the output fibers of Nucleus laminaris (NL), the anterior division of the ventral lateral lemniscal nucleus (VLVa), the core of the central nucleus of the inferior colliculus (ICcC), the lateral shell of the central nucleus of the inferior colliculus (ICcLS), and the external nucleus of the inferior colliculus (ICx).
The projections of nucleus angularis were found to terminate throughout most of the contralateral central nucleus except the dorsomedial portion at rostral levels, where the majority of the projections of Nucleus laminaris were concentrated. Nucleus angularis (and to a lesser extent Nucleus laminaris) was also found to have substantial projections to certain noncentral toral nuclei, in particular to the caudomedial shell nucleus of Puelles et al.
As regards the cochlear nuclei, we found that nucleus angularis derives from r3 to r6, Nucleus laminaris from r5 to r6, nucleus magnocellularis from r6 to r7 and nucleus olivaris superior from r5.
Higher resonant frequencies tended to predominate at relatively lower stations in the auditory pathway (approximately 100 Hz in the nucleus magnocellularis, 24 Hz in the Nucleus laminaris, 6 Hz in the nucleus ovoidalis).
Projections to the OS originate bilaterally in the cochlear nuclei (nucleus angularis) and the Nucleus laminaris. Glycine-transporting cells were found ipsilaterally in the nucleus angularis and the Nucleus laminaris.
These included neurons of nMAG, the nucleus angularis, the Nucleus laminaris, the cochlear ganglion, the Purkinje cell layer of the cerebellum, the ventral horn of the spinal cord, and the brainstem nucleus of the glossopharyngeal nerve (ncIX).
Microelectrode recordings of spontaneous multiple unit activity were made from nucleus magnocellularis (NM) and Nucleus laminaris (NL), second- and third-order nuclei in the chick auditory system, between 14 and 19 d of incubation (E14-E19).
No ChAT-I neurons or fibers were observed in NM, nucleus angularis, Nucleus laminaris, in the nuclei of the lateral lemniscus, or in the nucleus mesencephalicus lateralis pars dorsalis.
Retrogradely labelled cells were found in the Nucleus laminaris of the torus semicircularis and in the nuclei of mesencephalic tegmentum.
A major descending projection originated from the griseum centrale (including the Nucleus laminaris of the torus semicircularis), while minor areas of origin, apart from isolated reticular cells, were the nucleus and the interstitial nucleus of the fasciculus longitudinalis medialis, the red nucleus, the locus coeruleus and the raphe nuclei.
In the bird auditory brainstem, Nucleus laminaris neurons compute interaural time differences by comparing inputs from two ears.
Surgical destruction of the otocyst in chick embryos prevents formation of the *** ear, abolishes normal cochlear input to the cochlear nucleus (nucleus magnocellularis, NM) and results in axons from the contralateral NM forming (in addition to their normal bilateral endings in Nucleus laminaris, NL) a novel and functional aberrant projection to the deafferented NM.
Unilateral cochlea removal led to a strong reduction of activity in the cochlear nuclei and the Nucleus laminaris, whereas there was no remarkable effect in higher brainstem centers.
The circuit from the cochlear nucleus magnocellularis to the Nucleus laminaris supports the encoding and measurement of interaural time differences in the auditory brainstem. The axonal projections of magnocellular neurons to the Nucleus laminaris form maps of interaural time difference. The cells in the low best frequency region of the Nucleus laminaris have longer dendrites..
Neurons in Nucleus laminaris (NL) of birds are the first to receive binaural information and are presumed to play a role in encoding interaural time differences (ITDs).
Moreover, staining patterns with acetylcholinesterase were complementary to those previously reported with an anti-calbindin antibody, which stains terminal fields of Nucleus laminaris, and thus stains all the nuclei and subdivisions of nuclei that belong to the time pathway.
The nucleus isthmo-opticus, nucleus magnocellularis cochlearis, and Nucleus laminaris all express high levels of SERCA2 but with different ratios of SERCA2b and SERCA2a.
Delays of neurophonic potentials (NP) induced by monaural sound stimuli were measured across the three dimensions in the Nucleus laminaris (NL) of the anesthetized chicken.
Third-order auditory neurons in the avian Nucleus laminaris (NL) are the first to receive binaural input.
NM projects exclusively to the third-order neurons of Nucleus laminaris (NL).
A monoclonal antibody to the GABAR/benzodiazepine/chloride channel complex and radiolabeled ligand binding using [ 3H]-muscimol, a GABA agonist, revealed labeling in nucleus magnocellularis (NM), Nucleus laminaris (NL), nucleus angularis (NA), and the superior olive (SO) in both posthatch and embryonic chicks.
Neuronal selectivity for ITD is generated in the Nucleus laminaris (NL) and conveyed to both the anterior portion of the ventral nucleus of the lateral lemniscus (VLVa) and the central (ICc) and external (ICx) nuclei of the inferior colliculus.
magnocellularis, NM) to third-order auditory neurons in Nucleus laminaris (NL) of the chicken were studied using in vitro brain slices, bath application of drugs, and electrophysiological recording of postsynaptic field potentials.
In contrast, the nuclei with essentially or exclusively sensory components (i.e., nucleus angularis, Nucleus laminaris, nucleus magnocellularis) arise from the alar plate.
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. 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..
The lateral branch becomes the recurrent ipsilateral collateral; the medial branch crosses the midline, heading toward the contralateral target site in the region of the presumptive Nucleus laminaris. Neuroblasts destined for Nucleus laminaris migrate coincidentally with magnocellularis neuroblasts.
Because such changes in the central nervous system are often associated with changes in local blood flow, we examined blood flow in second-order auditory nucleus magnocellularis (NM) and third-order Nucleus laminaris (NL).
Surgical removal of the otocyst in chick embryos induces axons from the contralateral cochlear nucleus (nucleus magnocellularis, NM) to form, in addition to their normal endings in Nucleus laminaris (NL), anomalous and persistent functional contacts in the ipsilateral NM (Jackson and Parks, 1988).
The second- and third-order auditory nuclei in the brainstem of the chicken, nucleus magnocellularis (NM) and Nucleus laminaris (NL), receive afferents that are immunoreactive to gamma-aminobutyric acid (GABA).
In the time pathway, all the cells of the cochlear nucleus magnocellularis and Nucleus laminaris receive perisomatic GABAergic terminals, and small numbers of GABAergic neurons surround both nuclei.
The development of gamma-aminobutyric acid-immunoreactivity (GABA-I) in nucleus magnocellularis (NM) and Nucleus laminaris (NL) of the chick was studied by using an antiserum to GABA.
During embryonic development, little Gly-I is present in nucleus magnocellularis (NM), Nucleus laminaris (NL), or nucleus angularis (NA).
The representation of ipsilateral space is found in the "core" of the ICc, a subdivision defined by the terminal field of Nucleus laminaris, the avian analogue of the medial superior olivary nucleus. The representation of ipsilateral space in the core of the ICc may be accounted for by the crossed projection from the Nucleus laminaris because most of the Nucleus laminaris is devoted to a representation of contralateral space.
This study describes qualitative and quantitative changes in dendritic ultrastructure during the rapid atrophy of Nucleus laminaris (NL) dendrites following deafferentation.
At the level of the Nucleus laminaris, the difference in phase angle of corresponding spectral components in the left and right ears is extracted. The central nucleus core is innervated by the contralateral Nucleus laminaris, which contains a representation of contralateral space.
The well-developed cochlear nuclear complex includes the nucleus angularis, nuclei magnocellulares medialis and lateralis, and Nucleus laminaris. The primary cochlear fibers coursing in the posterior root terminate in nucleus angularis, nuclei magnocellulares medialis and lateralis, and the inner cell strand of Nucleus laminaris.
In the barn owl (Tyto alba) neuronal sensitivity to this disparity originates in the brainstem Nucleus laminaris. Afferents from the ipsilateral and contralateral magnocellular cochlear nuclei enter the Nucleus laminaris through its dorsal and ventral surfaces, respectively, and interdigitate in the nucleus. Thus, these afferent axons act as delay lines and provide anatomical and physiological bases for a neuronal map of interaural time differences in the Nucleus laminaris..
Lobus parolfactorius and nucleus vestibularis medialis were labelled by only MAb 270, whereas only MAb 35 labelled Nucleus laminaris and the medial and lateral pontine nuclei.
NM projects solely and bilaterally to Nucleus laminaris (NL), wherein interaural phase difference is computed.
NM projects solely, bilaterally, and tonotopically to Nucleus laminaris (NL).
The aberrant projection arises as a vertically directed branch from the contralaterally traveling NM axon at the medial border of Nucleus laminaris (NL).
We found that a few cells in the lentiformis mesencephali project to the medial pontine nucleus, but that a much heavier projection arises from the Nucleus laminaris precommissuralis, which is medial to the nucleus lentiformis mesencephali, pars medialis.
Studies of the avian auditory system indicate that neurons in nucleus magnocellularis (NM) and Nucleus laminaris of young animals are dramatically altered by changes in the auditory receptor.
Cells were labelled in the following nuclei, listed from rostral to caudal: nucleus entopeduncularis anterior, nucleus anterior thalami, nucleus posterior thalami, nucleus ventromedialis thalami, nucleus ventrolateralis thalami pars dorsalis, nucleus lateralis thalami pars posterodorsalis, nucleus neuropilis postthalamici, nucleus lentiformis mesencephali, nucleus praetectalis, Nucleus laminaris tori semicircularis, nucleus principalis tori semicircularis, nucleus magnocellularis tori semicircularis, nucleus profundus mesencephali, nucleus anterodorsalis tegmenti, nucleus posterodorsalis tegmenti, nucleus posteroventralis tegmenti, nucleus isthmi, nucleus lineae lateralis pars rostralis, nucleus lineae lateralis pars caudalis, nucleus intermedius, nucleus lateralis nervi octavi, nucleus descendens nervi trigemini, nucleus reticularis superior, nucleus reticularis medius, nucleus reticularis inferior, nucleus reticularis lateralis, nucleus cuneatus and area dorsalis medullae spinalis.
Using an antiserum directed against gamma-aminobutyric acid (GABA), the presence of presumed GABAergic neurons is demonstrated in the chicken auditory brainstem nuclei: Nucleus laminaris, nucleus angularis, superior olive, and the ventral nuclei of the lateral lemniscus.
The third-order auditory neurons of the avian Nucleus laminaris (NL) have distinct dorsal and ventral dendritic tufts that receive their predominant synaptic input from, respectively, the ipsilateral and contralateral cochlear nucleus.
Nucleus laminaris (NL) is the site at which the timing of sounds arriving in the 2 ears is compared in the auditory system of the barn owl.
The tonotopic organization of nucleus magnocellularis and Nucleus laminaris, second and third order nuclei in the avian auditory system, was mapped in 19-20-day old chick embryos (E19-20).
Neurons of the barn owl's (Tyto alba) Nucleus laminaris, the first site of binaural convergence, respond in a phase-locked fashion to a tone delivered to either ear. The phase of a tone-induced evoked potential, termed "neurophonic," varies systematically with position in Nucleus laminaris. Thus, Nucleus laminaris presumably measures and maps interaural phase differences by using the principles of delay lines and coincidence detection..
In the binaural Nucleus laminaris, the asymmetrical and almost mirror-imaged labeling pattern (Lippe, Stewart, and Rubel: Brain Res.
Auditory responses to tone pips were found in the Nucleus laminaris and principalis in caudomedial regions of the torus semicircularis, in areas lying medial to the main centers of lateral line evoked activity; this is a similar organisation to that found in teleost fish.
In the third experiment, the highly polarized Nucleus laminaris of a chick was specially prepared so that one set of its excitatory afferents could be stimulated without concurrent stimulation of the other set.
Ascending auditory projections to the nucleus mesencephalicus lateralis pars dorsalis (MLd) were studied in white Leghorn chickens by means of unilateral injections of horseradish peroxidase into the MLd and by injections of tritiated leucine into nucleus angularis or the combined nucleus magnocellularis and Nucleus laminaris. Projections from Nucleus laminaris were demonstrated to the ipsilateral superior olive, to the contralateral lemniscal nuclei and a small medial region in MLd bilaterally; the contralateral projection is much denser than the ipsilateral one. Although several of these findings correspond with auditory connections previously shown in the pigeon brainstem, they differ fundamentally in that we find both nucleus angularis and Nucleus laminaris projecting to different areas of the MLd on both sides of the brain.
In the present study this prediction was tested by using microelectrode recording procedures to map the tonotopic organization of nucleus magnocellullaris (NM) and Nucleus laminaris (NL), first- and second-order auditory nuclei, in chickens at three ages: embryonic day 17, 1 day posthatch, and 2-4 weeks posthatch.
The time course and specificity of the changes in dendritic morphology following deafferentation were examined in Nucleus laminaris of young chickens. The dendrites of Nucleus laminaris neurons are segregated into dorsal and ventral domains, which are innervated separately from the ipsilateral and contralateral nucleus magnocellularis, respectively. Transection of the crossed dorsal cochlear tract deafferents the ventral dendrites of Nucleus laminaris bilaterally without interrupting the matching input to the dorsal dendrites.
However, Golgi impregnation revealed abnormalities in the length and structure of the dendrites in Nucleus laminaris.
Nucleus magnocellularis and Nucleus laminaris in the avian brainstem contain second- and third-order auditory neurons thought to be homologous to the mammalian anteroventral cochlear nucleus and medial superior olivary nucleus, respectively. Nucleus laminaris in the chicken is a tonotopically organized sheet of bipolar neurons; each of these neurons receives spatially segregated bilateral innervation from the two magnocellular nuclei. We suggest that the elongated terminal fields provide the basis of the tonotopic organization observed in Nucleus laminaris and that the trajectories of the ipsilateral and contralateral axons may provide differential conduction delays that are important for binaural integration of acoustic information..
The axonal endings on the somata and dendrites of third-order auditory neurons in Nucleus laminaris (NL) were measured and classified in thin-sectioned material from adult chickens.
The optic fiber was found to partially decussate at the chiasm and to project to 5 contralateral regions: (1) hypothalamus (area optica hypothalami); (2) thalamus (area optica dorsalis thalami, area optica mediale thalami, nucleus thalamicus tractus optici marginalis, Nucleus laminaris ventralis); (3) pretectum (nucleus pretectalis ventralis, nucleus commissurae posterioris, nucleus intercalaris lateralis); (4) optic tectum (superficial layers); and (5) mesencephalic tegmentum (area optica accessoria).
Nucleus laminaris responses to direct stimulation of n.
In the binaurally innervated cells of the Nucleus laminaris the symmetry of the dorsal and ventral dendritic trees normally increases during the embryonic and early postnatal period.
Synaptic potentials were examined in the second- and third-order auditory neurons of nucleus magnocellularis and Nucleus laminaris in the chick.
By embryonic day 10, efferent axons have already grown out from the cells and characteristic terminal plexuses of these axons are seen in Nucleus laminaris bilaterally.
In addition, cells and axons in Nucleus laminaris, the presumed homologue of the mammalian medial superior olivary nucleus, are also described. Evidence is presented that individual axons from the nucleus magnocellularis bifurcate and send branches to the Nucleus laminaris bilaterally, thus placing constraints on the binaural interactions possibly involved in lateralization functions. This should, in turn, allow a secure relay of bilateral latency differences essential for binaural interactions in the Nucleus laminaris..
Nucleus laminaris (NL) is a third-order auditory nucleus in the avian brain stem which receives spatially segregated binaural inputs from the second-order nuclei magnocellularis.
Neurons in Nucleus laminaris of the torus semicircularis were retrogradely labeled following application of horseradish peroxidase (HRP) to the cervical spinal cord in two lizards (Gekko gecko and Iguana iguana) and a turtle (Pseudemys scripta).
The effect of unilateral basilar papilla removal on glucose uptake in the 2nd and 3rd order auditory nuclei in the chick's brain stem, nucleus magnocellularis and Nucleus laminaris, respectively, was examined with [ 3H]2-deoxy-D-glucose (2-DG) autoradiography. It was observed that there is a greater density of grains over the neuropil regions of Nucleus laminaris which receive input from the normal ear than over the corresponding regions which receive input from the operated ear. Similarly, differences in grain density are found between the normally innervated and deafferented magnocellular nuclei although these differences are not as great as those in Nucleus laminaris. Differences in grain density were also apparent between the glial/fiber regions which bound the neuropil areas of Nucleus laminaris; there is a greater density of grains overlying those glial/fiber regions through which fibers receiving input from the normal ear course than over those regions through which fibers which normally carry input from the operated ear travel. The present results thus show the neuropil regions of Nucleus laminaris and the adjacent glial/fiber areas to be areas of high glucose utilization.
A small but well-defined secondary nucleus which showed no degenerated nerve terminals after nerve root section, Nucleus laminaris, underlies the cephalic part of both nucleus magnocellularis medialis and nucleus magnocellularis lateralis.
Nucleus laminaris and n.
Nucleus laminaris (NL) is a third-order auditory nucleus in the avian brain stem which receives spatially-segregated binaural inputs from the second-order magnocellular nuclei.
A probably secondary cochlear nucleus, Nucleus laminaris, lies just ventral to the nucleus magnocellularis. Nucleus laminaris remains free of terminal degeneration after destruction of the posterior eighth nerve and ganglion.
Of particular interest was the question of whether Nucleus laminaris (NL) receives primary afferents.
The Nucleus laminaris (NL), a third-order brain stem auditory nucleus in birds, receives afferents to its dorsal dendrites from the ipsilateral nucleus magnocellularis (NM), while the ventral dendrites of NL neurons are innervated by axons from the contralateral NM via the crossed dorsal cochlear tract (CTrX).
Nucleus magnocellularis (NM) and Nucleus laminaris (NL) are, respectively, second- and third-order auditory nuclei in the chicken brain stem.
The tonotopic and topographic organization of the bilateral projection from second-order auditory neurons of nucleus magnocellularis (NM) to Nucleus laminaris (NL) was examined in young chickens.
The normal anatomy of the three cochlear nuclei in the hen, the Nucleus laminaris, the nucleus angularis and the nucleus magnocellularis is described. The part of Nucleus laminaris which consists of a ventral convex sheet of cells is shown to receive cochlear nerve fibers from both ears, the nerve fibers from the ipsilateral ear terminating dorsal to the cell sheet while contralateral nerve fibers terminate ventral to the nerve cells. The cochlear ganglion cells projecting to the Nucleus laminaris are apparently situated in other parts of the ganglion that the cells projecting to the nucleus angularis and magnocellularis.
Nucleus laminaris may be represented by a few fusiform cells in the ventral portion of the NML region..
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