Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cochlear Nucleus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,729 records · Page 96Linked to original sources
PubMed1995

Distribution of nitric oxide synthase in the central nervous system of Macaca fuscata: subcortical regions.

The distribution of nitric oxide synthase-immunoreactive neurons was studied in the Macaca fuscata by immunohistochemistry using antiserum against nitric oxide synthase. In the macaque lower brainstem, many nitric oxide synthase-containing cell bodies were found in the gigantocellular and parvocellular reticular nuclei, the nucleus of the spinal tract of trigeminal nerve, the cochlear nucleus, the prepositus hypoglossi and the nucleus of the solitary tract. Many nitric oxide synthase-immunoreactive perikarya were observed in the laterodorsal-pedunculopontine tegmental nucleus complex of the macaque pontine and midbrain tegmentum. In addition, there were many highly immunoreactive cell bodies in the superficial layers of the inferior and superior colliculi. In the forebrain, numerous cell bodies were observed in the caudate nucleus, putamen, nucleus accumbens, nucleus of the diagonal band, anterior perforated substance and amygdaloid complex. Whereas most of these neurons were labeled highly intense for nitric oxide synthase, there were also many lightly labeled nitric oxide synthase-immunoreactive neurons in the substantia innominata, globus pallidus, ansa peduncularis and lateral hypothalamic nucleus. The present observation indicated some species difference in the distribution of central nitric oxide synthase-containing neurons. Furthermore, the present neuroanatomical evidence that nitric oxide synthase is distributed in a variety of specific neuronal systems, with some differences in the patterns of cytoplasmic localization, further indicates the neural messenger role of nitric oxide in the central nervous system.

Amino Acid Oxidoreductases↗
PubMed1991

Frequency representation and spiral ganglion cell density in the cochlea of the gerbil Pachyuromys duprasi.

The tonotopic map of the cochlea in the gerbil Pachyuromys duprasi was analysed by local iontophoretic HRP-application into physiologically defined regions of the cochlear nucleus and mapping of subsequent HRP transport patterns in cochlear spiral ganglion cells. Furthermore the spiral ganglion cell density along the cochlear duct was determined. The cochlear tonotopic map was established in the frequency range between 0.6 and 17.5 kHz. These frequencies corresponded to locations between 86 and 3% basilar membrane length (0% = cochlear base). It was found that the slope of the place-frequency map varied with frequency, the maximum slope being found between 1 and 4 kHz. This frequency range corresponds to the frequency range of highest auditory sensitivity as determined from cochlear microphonic recordings (Plassmann et al., 1987). The density of spiral ganglion cells also varied along the cochlear duct. A pronounced maximum (1927 cells/mm) was located at around 70% basilar membrane length, compared to values of 800 cell per mm near the cochlear apex and base. This region of high ganglion cell density also corresponds to the frequency range of highest auditory sensitivity.

Acoustic Stimulation↗
PubMed1994

Localization of nitric oxide synthase in the adult rat brain.

The distribution of the immunoreactivity to nitric oxide synthase has been examined from rostral to caudal areas of the rat central nervous system using light microscopy. Endogenous nitric oxide synthase was located using a specific polyclonal antiserum, produced against affinity purified nitric oxide synthase from whole rat brain, following the avidin-biotin peroxidase procedure. Immunoreactive cell bodies and processes showed a widespread distribution in the brain. In the telencephalon, immunoreactive structures were distributed in all areas of the cerebral cortex, the ventral endopiriform nucleus and claustrum, the main and accessory olfactory bulb, the anterior and posterior olfactory nuclei, the precommisural hippocampus, the taenia tecta, the nucleus accumbens, the stria terminalis, the caudate putamen, the olfactory tubercle and islands of Calleja, septum, globus pallidus and substantia innominata, hippocampus and amygdala. In the diencephalon, the immunoreactivity was largely found in both the hypothalamus and thalamus. In the hypothalamus, immunoreactive cell bodies were characteristically located in the perivascular-neurosecretory systems and mamillary bodies. In addition, immunoreactive nerve fibres were detected in the median eminence of the infundibular stem. The mesencephalon showed nitric oxide synthase immunoreactivity in the ventral tegmental area, the interpeduncular nucleus, the rostral linear nucleus of the raphe and the dorsal raphe nucleus. Immunoreactive structures were also found in the nuclei of the central grey, the peripeduncular nucleus and substantia nigra pars lateralis, the geniculate nucleus and in the superior and inferior colliculi. The pons displayed immunoreactive structures principally in the pedunculopontine and laterodorsal tegmental nuclei, the ventral tegmental nucleus, the reticulotegmental pontine nucleus, the parabrachial nucleus and locus coeruleus. In the medulla oblongata, immunoreactive neurons and processes were detected in the principal sensory trigeminal nucleus, the trapezoid body, the raphe magnus, the pontine reticular nuclei, the supragenual nucleus, the prepositus hypoglossal nucleus, the medial and spinal vestibular nuclei, the dorsal cochlear nucleus, the medullary reticular field, the nucleus of the solitary tract, the gracile and cuneate nuclei, the dorsal nucleus of the vagus nerve and the oral, interpolar and caudal parts of the spinal trigeminal nucleus. In the cerebellum, the stellate and basket cells showed immunoreactivity, which was also seen in the basket terminal fibres of the Purkinje cell layer. Isolated immunoreactive Purkinje cells were found in the vermis and parafloccular regions of the cerebellum. In the granular layer of the cerebellum, the granular cells and glomeruli were also immunoreactive. Numerous positive varicose nerve fibres and occasional neurons were also found in the lateral and interposed cerebellar nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Oxidoreductases↗
PubMed1989

Comparative distribution of three opioid systems in the lower brainstem of the monkey (Macaca fuscata).

The regional distribution of the three opioid peptide neuronal systems--proopiomelanocortin (POMC), proenkephalin A, and proenkephalin B--was investigated in the lower brainstem of Japanese monkeys (Macaca fuscata) by immunocytochemical techniques. Antiserum to beta-endorphin/beta-lipotropin, [Met]-enkephalin-Arg6-Gly7-Leu8, and human leumorphin were used to identify the POMC and the proenkephalin A and B systems, respectively. POMC-related immunoreactive material was not found in the neuronal perikarya in the lower brainstem; reactive fibers and apparent terminals were distributed in the substantia nigra, lemniscus lateralis, midbrain central gray, the nucleus raphes, nucleus parabrachialis lateralis, ventral area of the spinal trigeminal nerve, nucleus tractus solitarii, and in the reticular formation throughout the lower brainstem. Proenkephalin A-related immunoreactive neuronal perikarya were detected in the central gray, reticular formation, nucleus raphes, trapezoid body, nucleus parabrachialis lateralis and medialis, nucleus spinalis nervi trigemini, nucleus dorsalis nervi vagi, and in the nucleus tractus solitarii. Densely packed immunoreactive fibers were widely distributed in the substantia nigra, nucleus interpeduncularis, nucleus raphes, superior colliculus, periaqueductal central gray, nucleus parabrachialis lateralis and medialis, locus coeruleus, trapezoid body, nuclei cochleares, nucleus spinalis nervi trigemini, tractus spinalis nervi trigemini, nucleus tractus solitarii, nucleus dorsalis nervi vagi, nucleus gracilis, nucleus cuneatus, nucleus cuneatus accessorius, and in the reticular formation throughout the lower brainstem. Neuronal perikarya containing immunoreactive material related to proenkephalin B were found in the periaqueductal central gray, nucleus parabrachialis lateralis and medialis, nucleus tractus solitarii, and nucleus spinalis nervi trigemini. In addition, immunoreactive fibers were detected in the ventral tegmental area, substantia nigra, nucleus parabrachialis lateralis and medialis, nucleus vestibularis lateralis and medialis, and in some areas of the reticular formation. These anatomical findings demonstrate that these three opioid peptide neuronal systems are widely but uniquely distributed in the lower brainstem of the monkey.

Animals↗
PubMed1982

Changes in rapidly transported proteins in the auditory nerve after hair cell loss.

In an effort to further characterize the proteins of the auditory nerve, the effects of hair cell loss on rapidly transported proteins of the auditory nerve were studied. The effects were studied in the waltzing guinea pig, a genetically deaf animal which displays an age-dependent loss of sensory cells, and in normal guinea pigs treated with neomycin. In both cases hair cell loss is followed by a slow degeneration of spiral ganglion cells and corresponding auditory nerve fibers. Rapidly transported proteins in the cochlear nucleus were analyzed by two dimensional electrofocusing/electrophoresis 3 h after cochlear injection of [35S]methionine. In both the waltzing guinea pig and the neomycin-treated animals, a significant increase in labeling of two series of polypeptides (average molecular weights of 27,000 and 36,000 daltons) was apparent. Quantitation of the 36,000 dalton protein by extracting from dried gels showed a 2-fold increase in the 10-day-old waltzing guinea pig and a 6-fold increase in the 80-day-old waltzing guinea pig. Further analysis shows these proteins to be membrane-associated glycoproteins.

Animals↗
PubMed1998

Brainstem pathology of infantile Gaucher's disease with only wave I and II of auditory brainstem response.

We studied the auditory brainstem response (ABR) and neuropathology in a female infant who died at six months of age because of typical infantile Gaucher's disease. The patient was hospitalized for hepatosplenomegaly and failure to thrive. Her ABR showed only waves I and II. The neuropathological study disclosed that: (1) Gaucher's cells were found in the perivascular region of the cerebrum and anterior ventral nucleus of the thalamus. (2) Gliosis was found in the dorsal part of the brainstem rather than the ventral part. (3) Neuronal cells in the superior olivary nucleus were lost, and marked gliosis was found in the cochlear nucleus. The disappearance of wave III and later waves of ABR could be supported by these pathological findings.

Brain Stem↗
PubMed1997

Labeling of musical interval size by cochlear implant patients and normally hearing subjects.

OBJECTIVE: To compare the performance of cochlear implant patients and normal-hearing subjects on a musical interval labeling task, and to determine whether information regarding musical interval size is available to cochlear implant patients under realistic everyday listening conditions. DESIGN: Two Nucleus cochlear implant patients listened to musical intervals that consisted of systematic variations of electric pulse rate on single bipolar intracochlear electrode pairs, whereas normal-hearing listeners were presented with the acoustical analog of these stimuli. Subjects labeled the intonation quality of the stimulus intervals ("flat," "sharp," or "in tune"), relative to their memory for specific intervals abstracted from familiar melodies. The cochlear implant patients, in addition, performed this task with realistic acoustical musical stimuli. RESULTS: The interval labeling behavior of cochlear implant subjects, at low pulse rates, was similar to that of normal-hearing subjects. Furthermore, pitch interval information does not appear to be available to cochlear implant subjects when they are listening to acoustical stimuli via their speech processors. CONCLUSIONS: Temporal information appears to be sufficient for the perception of musical pitch. Encoding strategies that are highly successful in restoring speech understanding do not necessarily provide information regarding melodic pitch interval size.

Auditory Perception↗
PubMed1999

Physiologic identification of eighth nerve subdivisions: direct recordings with bipolar and monopolar electrodes.

The purpose of this study was to determine stimulation and recording parameters that maximize differences in evoked responses recorded between the cochlear nerve and the surrounding tissues. Click-evoked potentials were obtained using monopolar and bipolar recording electrodes placed directly on the exposed eighth nerve of anesthetized cats. Responses were compared as stimulus intensity, electrode location, and bipolar electrode orientation and interelectrode spacing were systematically varied. Wave amplitudes increased monotonically with intensity for both monopolar and bipolar configurations, but bipolar configurations exhibited greater selectivity in differentiating cochlear from vestibular subdivisions. The optimal stimulus intensity was 70 to 80 dB peak sound pressure level (pSPL). Monopolar recordings were often confounded by activity originating at remote sites, typically the cochlear nucleus and (for recording sites on the vestibular nerve) the cochlear nerve. Bipolar response amplitudes increased with interelectrode spacing and were largest when electrodes were oriented parallel to the long axis of the nerve. Extrapolation of empirical data indicated that amplitudes of bipolar responses would be maximal at an electrode separation of 7.5 mm. Cochlear nerve conduction velocity, calculated from wave latencies at each of the two monopolar electrodes, was 11.6 +/- 1.6 m/sec.

Animals↗
PubMed1991

Localization of mercury in CNS of the rat. III. Oral administration of methylmercuric chloride (CH3HgCl).

The distribution and cellular localization of mercury in the in situ brain and upper cervical spinal cord of adult Wistar rats were studied at various time intervals after oral administration of methylmercuric chloride (CH3HgCl; 20 mg x liter-1). Coronal sections of the brain and transverse sections of the cervical spinal cord were prepared for visualization of the mercury by the autometallographic silver-enhancement method. Following mercury administration there was a latent period before the metal appeared in the tissue. Mercury staining was first detected after 10 days in cell bodies of five specific areas of the brain stem: the mesencephalic nucleus of the trigeminal nerve, the red nuclei, the ventral cochlear nucleus, the superior vestibular nucleus, and the nucleus reticularis pontis caudalis. After 28 days of treatment, a fairly even distribution of mercury was seen in the brain and spinal cord. Longer periods of treatment caused no further increase in the density of mercury within the stained cell bodies. In cerebral cortex, staining commenced in piriform and entorhinal cortices. This was followed by staining in neurons of lamina III in the isocortex and ultimately all layers were stained after 28 days of treatment. After 20 days of treatment, mercury deposits in the cerebellar cortex were restricted to Purkinje cells, Golgi epithelial cells, and Golgi cells, while in the spinal cord the majority of mercury was located in the anterior horn motoneurons. Scattered ependymal cells and epithelial cells of the choroid plexus also exhibited mercury staining. The principal target cells were neurons followed by the glial and ependymal cells. Ultrastructurally, the bulk of detectable mercury was localized in lysosomes.

Animals↗
PubMed1998

Plastic changes in glycine and GABA release and uptake in adult brain stem auditory nuclei after unilateral middle ear ossicle removal and cochlear ablation.

[i] In young adult guinea pigs, the effects of unilateral ossicle removal and unilateral cochlear ablation were determined on [14C]glycine or [14C]GABA release and uptake measured in subdivisions of the cochlear nucleus (CN), the superior olivary complex, and the auditory midbrain, after 2 or 5, 59, and 145 postlesion days. Activities were compared to those of age-matched, unlesioned controls. [ii] [14C]Glycine release declined bilaterally in the anteroventral and dorsal CN after ossicle removal and in the dorsal CN after cochlear ablation. [iii] Transient elevations of release occurred at 59 days in the ipsilateral posteroventral CN ([14C]glycine) and bilaterally in the ventral nucleus of the lateral lemniscus ([14C]GABA) after ossicle removal, and bilaterally in the medial superior olive ([14C]glycine) after cochlear ablation. [iv] In the medial nucleus of the trapezoid body, [14C]GABA release was depressed bilaterally 5 days after ossicle removal, but was elevated at 145 days contralaterally after ossicle removal and ipsilaterally after cochlear ablation. [v] In the contralateral central nucleus of the inferior colliculus, [14C]GABA release was elevated persistently after ossicle removal. After cochlear ablation, release was elevated at 5 days, near the control at 59 days, and elevated again at 145 days. [vi] After both lesions, [14C]glycine uptake was elevated bilaterally in the CN and medial superior olive. [14C]GABA uptake became depressed by 59 or 145 days bilaterally in the auditory midbrain. [vii] These changes may stem from regulation and may contribute to mechanisms that generate symptoms such as loudness recruitment and tinnitus, which often accompany hearing loss.

Age Factors↗
PubMed1997

Speech perception by prelingually deaf children and postlingually deaf adults with cochlear implant.

We review recent data from the University of Iowa obtained from prelingually deaf children over 3 years using feature-extraction versions of the Nucleus cochlear implant, and from postlingually deaf adults using the compressed-analog Ineraid, a feature-extraction version of Nucleus, and a continuous interleaved sampling version of the Clarion cochlear implant. Both adults and children were followed over a 3-year period. Average results are shown where each patient is represented at each point in time. Results for the children show continued improvement over the 3-year period, with some children obtaining maximum scores possible on the easier closed-set tests. Substantial improvements in audiovisual enhancement were provided by the cochlear implant. Results from the adults show maximum gains within the first year of implant use, although some patients show continued improvements after 2 years of implant use. Adults who have been deaf for several years and who receive their implant when they are older tend not to perform as well as adults who have been deaf for only a few years or receive their implant when they are younger.

Adult↗
PubMed1981

Age- and position-dependent effects of monaural acoustic deprivation in nucleus magnocellularis of the chicken.

The effect of a moderately severe monaural conductive hearing loss on the development of neuronal size in the avian nucleus magnocellularis (NM) was investigated. NM is considered to be the homologue of the mammalian anteroventral cochlear nucleus and receives large calyceal synaptic endings from the cochlear nerve. Silicone plastic earplugs which produce a 40 dB broadband conductive hearing loss were placed in one external auditory canal of chick embryos on the 18th day of incubation. After hatching, all animals were housed in communal brooders and sacrificed at 4, 10, 25, and 60 days of age. Nissl-stained sections from paraffin- and plastic-embedded brains were used to sample neuronal cross-sectional areas in NM on the deprived and nondeprived sides of the brain. These samples were obtained separately in each brain from three posterior-to-anterior percentage quartiles within NM. Statistical analyses of these data showed that the severity of deprivation-induced cell size changes in NM varied as a function of both age and position. In the 4- and 10-day groups, no significant deprived-versus-nondeprived differences in neuronal size were seen in any area of the nucleus. At 25 days after hatching, only the third posterior-to-anterior quartile (i.e., 50-74%) showed a significant difference; this difference was also significantly greater than those in the second and fourth quartiles at this age. By 60 days, all three sampled areas in NM showed highly significant differences (averaging 12%) in mean neuronal cross-sectional area. Cell size values from the deprived and nondeprived sides of 60-day-old experimental animals were also compared with values from 60-day-old control subjects. Whereas the deprived NM cells were significantly smaller than controls, there was no evidence for a reliable hypertrophy in the nondeprived cells. Thus, the principal effect of the acoustic deprivation produced was to retard continued growth of the deprived neurons after 4 days of age.

Animals↗
PubMed1991

Frequency representation in the rat cochlea.

In order to determine the place-frequency map of the rat cochlea, iontophoretic HRP-injections were made into the cochlear nucleus at electrophysiologically characterized positions. Distribution of retrograde HRP transport in cochlear spiral ganglion cells was analysed by means of a three dimensional reconstruction of the cochlea. The map was established for frequencies between 1.2 and 54 kHz, corresponding to positions between 96.5 to 2% of basilar membrane length (base = 0%). At apex of the cochlea the slope of the place-frequency map was below 0.25 mm/octave. The slope increased to a value of 2.1 mm/octave at 34% basilar membrane length, and remained almost constant towards the cochlear base. The close relationship between frequency range of highest sensitivity and maximum receptor- and innervation-density in the rat cochlea is discussed.

Acoustic Stimulation↗
PubMed1991

Developmental changes of frequency representation in the rat cochlea.

The place-frequency map of the developing rat cochlea was measured by iontophoretic HRP-injections into the ventral cochlear nucleus at electrophysiologically characterized positions. Distribution of retrograde HRP transport in cochlear spiral ganglion cells was analysed by means of a three dimensional reconstruction of the cochlea. Cochlear place-frequency maps were derived in rats of two ages groups: 13 to 22 days, and 36/37 day old animals. These maps were compared with the place-frequency map of adult rats (Müller, 1991). No systematic difference in the place-frequency map between 36/37 day old and adult rats was observed. In animals of the younger age group the place-frequency map (for frequencies above 4 kHz) was shifted towards lower frequencies for a given place along the basilar membrane. The morphological and physiological basis for this frequency shift during development is discussed.

Acoustic Stimulation↗
PubMed1991

A computational model of afferent neural activity from the cochlea to the dorsal acoustic stria.

The first comprehensive computational model of the precortical mammalian auditory system to include afferent neural processing up to the level of the dorsal acoustic stria (DAS) is described. The model consists of two scissile stages simulating (1) the cochlea and auditory nerve (AN) and (2) the dorsal cochlear nucleus (DCN). The model derives its input from a 128-channel cochlear filterbank. Cochlear transduction, rectification, logarithmic compression, and two-tone suppression functions are performed at the first stage of the simulation. The 512 artificial neurons employed model the cell at the level of transmembrane potential and have interconnections that follow closely those reported in recent anatomical and physiological studies of the cat AN and DCN. The responses of the model to pure-tone stimuli (at various sound-pressure levels) and noise stimuli (at various levels and bandwidths) are reported in detail and compare well with published results. The model is being used to investigate the representation of initial English stop consonants (differing in voice-onset time) in the DAS; this work is briefly described.

Acoustics↗
PubMed2006

Improvement of phase information at low sound frequency in nucleus magnocellularis of the chicken.

Nucleus magnocellularis (NM) is one of the subnuclei of the avian cochlear nucleus and has a role of extracting the temporal information of sound from the auditory nerve fibers (ANFs). Neurons in NM are varied along the tonotopic axis in synaptic transmission and membrane excitability and are high-fidelity relay neurons at the high to middle characteristic frequency (CF) regions. Here we have compared the firing properties between ANFs and NM neurons in vivo and found that at high but not near threshold intensities, spike firings are more phase-locked in NM than in ANFs in the CF region <500 Hz. Moreover, NM shows reduced occurrence of multiple spikes within one cycle of sound stimuli and higher vector strength than ANF. The improved phase-locked firing nature of NM is discussed in relation to the in vitro findings of small EPSCs in the low CF neurons (Fukui and Ohmori 2004). It is concluded that NM neurons are not simple relay neurons in the low CF region but are coincidence detectors of monoaural synaptic inputs that improve the synchronization of spike firing to auditory inputs.

Acoustic Stimulation↗
PubMed1990

Classification of the temporal discharge patterns of single auditory neurons in the dorsal medullary nucleus of the northern leopard frog.

1. The dorsal medullary nucleus (DMN) of frogs is the presumed homolog of the mammalian cochlear nucleus (CN). Like the CN, the DMN is the sole target of centrally projecting primary auditory-nerve fibers and the first central auditory-processing center. To study the transformation of acoustic information in the DMN, we have utilized relatively simple stimuli--tone bursts--to detail the temporal discharge patterns of DMN neurons that can be compared with those shown by auditory-nerve fibers. 2. Based on the shape of poststimulus time (PSTH) and interspike interval (ISIH) histograms, we observed six distinctive discharge patterns to tone bursts presented at the best excitatory frequency (BEF), 10 dB above threshold. Four of these (primary-like type 1-4) resembled discharge patterns seen at the level of the auditory nerve, whereas two (phasic and phasic burst) were only observed in the DMN. 3. At stimulus levels of 20-30 dB above BEF threshold several phasic neurons became tonic responders, whereas several primary-like type-2 cells gave "pauser" discharges. The response patterns of the remaining cells were intensity independent. 4. We further showed that many of the single-unit discharge patterns were related to other neuronal response properties; specifically, spontaneous firing rate, intensity-rate functions, threshold, latency, BEF, and sharpness of tuning (Q10). 5. The implications of our findings are discussed with respect to 1) the transformation of acoustic information as it is passed from the auditory nerve to the DMN, and 2) the functional organization of the DMN.

Acoustic Stimulation↗