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PubMed1979

Neural representation of the acoustic biotope. A comparison of the response of auditory neurons to tonal and natural stimuli in the cat.

Cats were stimulated with tones and with natural sounds selected from the normal acoustic environment of the animal. Neural activity evoked by the natural sounds and tones was recorded in the cochlear nucleus and in the medial geniculate body. The set of biological sounds proved to be effective in influencing neural activity of single cells at both levels in the auditory system. At the level of the cochlear nucleus the response of a neuron evoked by a natural sound stimulus could be understood reasonably well on the basis of the structure of the spectrograms of the natural sounds and the unit's responses to tones. At the level of the medial geniculate body analysis with tones did not provide sufficient information to explain the responses to natural sounds. At this level the use of an ensemble of natural sound stimuli allows the investigation of neural properties, which are not seen by analysis with simple artificial stimuli. Guidelines for the construction of an ensemble of complex natural sound stimuli, based on the ecology and ethology of the animal under investigation are discussed. This stimulus ensemble is defined as the Acoustic Biotope.

Acoustic Stimulation↗
PubMed1985

Morphological changes in the cochlear nuclear complex in primate phylogeny and development.

The primate cochlear nuclear complex exhibits several characteristic morphological differences in the various primate families from Lorisidae through Hominidae. The most striking differences occur in the organization of the dorsal cochlear nucleus in which the laminar pattern becomes progressively obscured. Granule cells form an external granular layer as well as being intermixed within the molecular and pyramidal layers in slow lorises and squirrel and rhesus monkeys. Whereas a prominent external granular layer remains in chimpanzees, granule cells are scant in other portions of the nucleus. Human adults lack an external granular layer. A small number of granule cells occur but with inconstant distribution. Primates lack the linear array of pyramidal cells oriented perpendicularly to the epithelial surface as seen in cats. The granule cell layer exhibits similar regression in development of the human cochlear complex. The external granular layer is prominent in the fetus but rapidly decreases in size after birth. It achieves its adult form prior to 18 months. The data suggest that neuronal attrition, or programmed cell death, may be the major mechanism accounting for the alterations that occur in the human granule cell layer. Other differences in cytoarchitecture, within the great apes and humans, include decreases in the small and giant cell populations of the cochlear complex. These changes, in consort with the organizational changes and reduction of granule cells as noted above, suggest a trend towards reduced intranuclear integration at the level of the cochlear nucleus coupled with encephalization of the auditory system.

Adult↗
PubMed1998

Contrasting Ca2+ channel subtypes at cell bodies and synaptic terminals of rat anterioventral cochlear bushy neurones.

1. Whole-cell patch clamp recordings were made from bushy cells of the anterioventral cochlear nucleus (aVCN) and their synaptic terminals (calyx of Held) in the medial nucleus of the trapezoid body (MNTB). 2. Both high voltage-activated (HVA) and low voltage-activated (LVA) calcium currents were present in acutely dissociated aVCN neurones and in identified bushy neurones from a cochlear nucleus slice. 3. The transient LVA calcium current activated rapidly on depolarization (half-activation, -59 mV) and inactivated during maintained depolarization (half-inactivation, -89 mV). This T-type current was observed in somatic recordings but was absent from presynaptic terminals. 4. On the basis of their pharmacological sensitivity, P/Q-type Ca2+ channels accounted for only 6 % of the somatic HVA, while L-, N- and R-type Ca2+ channels each accounted for around one-third of the somatic calcium current. 5. The divalent permeabilities of these native calcium channels were compared. The Ba2+/Ca2+ conductance ratios of the somatic HVA and LVA channels were 1.4 and 0.7, respectively. The conductance ratio of the presynaptic HVA current was 0.9, significantly lower that that of the somatic HVA current. 6. We conclude that LVA currents are expressed in the bushy cell body, but are not localized to the excitatory synaptic terminal. All of the HVA current subtypes are expressed in bushy cells, but there is a strong polarity to their localization; P-type contribute little to somatic currents but predominate at the synaptic terminal; L-, N- and R-types dominate at the soma, but contribute negligibly to calcium currents in the terminal.

Algorithms↗
PubMed1962

Some effects of room acoustics on evoked auditory potentials.

Auditory potentials were recorded from bipolar electrodes chronically implanted in the cochlear nuclei of four cats. In a training box modified to reduce echoes these animals were exposed to clicks and tone pulses presented from an overhead speaker. Slight changes in the position of the animal in the resulting sound field produced marked changes in the potentials evoked from the cochlear nucleus. These phenomena were observed in the unanesthetized, unrestrained subjects as well as in those under Nembutal anesthesia. It is suggested that these acoustic effects complicate the analysis and interpretation of potentials evoked from the cochlear nucleus under conditions of habituation, shifts in attention, and learning.

Animals↗
PubMed1985

The cochlear nuclei--pathology.

This article is a sequel to one dealing with the anatomy of the cochlear nuclei. It employs the combined peripheral/central approach in reviewing some basic principles of the pathology of central deafness, involving the cochlear nuclei. The combined approach shows the relative status of the cochlear elements and of the superior ventral cochlear nucleus in various conditions. Anoxic encephalopathy, including that of erythroblastosis, involves the stated nucleus but spares the peripheral hearing organ. This, as well as the findings in other conditions, reflects on the employment of amplification or the implantation of electrodes. The spheroid cells, the nerve cells of concern of the superior ventral cochlear nucleus (SVCN), show an anatomic frequency gradient, low ventral to high dorsal. In any case of deafness expected to involve the SVCN and showing an audiogram frequency pattern, the frequency gradient must be included in the pathologic investigation. When the organ of Corti is completely destroyed, the spheroid cells may show transsynaptic atrophy.

Aged↗
PubMed1988

Development of aspartate aminotransferase and glutaminase immunoreactivity in the rat auditory nerve.

Aspartate aminotransferase and glutaminase immunoreactive labeling of the auditory nerve has previously been reported. In the present study, the development of these immunoreactivities was examined in the auditory nerve of the rat, at ages ranging from 17 days gestation to four postnatal weeks. Cells and processes were examined in the cochlea, and fibers and terminals in the cochlear nucleus. In the cochlea, immunoreactive labeling with antisera to both enzymes was first seen at 20 gestational days, in spiral ganglion cells. It was not until two postnatal weeks, however, that this immunoreactive labeling was first seen in primary afferent terminals around spherical cells in the anteroventral cochlear nucleus. This correlates with the establishment of mature synaptic connections and function.

Aging↗
PubMed2006

Intra- and postoperative electrode impedance of the straight and Contour arrays of the Nucleus 24 cochlear implant: relation to T and C levels.

The objective of this study was to investigate electrode impedance in cochlear implant recipients in relation to electrically evoked stapedius reflex measurements during surgery, and to electrode design, stimulation mode, and T and C levels over a nine month period after surgery. Seventy-five implant recipients, implanted with a Nucleus straight electrode array or a Contour array, were included. The results show that: (1) during surgery electrode impedance decreases markedly after electrically evoked stapedius reflex measurements, (2) after surgery, during the period without stimulation until speech processor switch-on, impedance increases, (3) after processor switch-on impedance decreases. The lower impedance values after a period of stimulation are found at the higher T and C levels. Impedances of the straight array electrodes are lower than those of the Contour array. The difference corresponds mainly to their respective surface areas. In addition, the straight array shows a larger increase of impedance in the apical direction than the Contour array, probably because of the larger fluid environment around the basal electrodes of the straight array.

Adolescent↗
PubMed1992

Spatial organization of the auditory nerve according to spontaneous discharge rate.

Auditory-nerve fibers in mammals have been classified into three functional subclasses according to spontaneous discharge rate (SR). In cat, the peripheral terminals of these SR groups are segregated around the sensory cell circumference (Liberman, '82, Science 216:1239-1241). The present study shows that this spatial segregation is at least partly maintained through the peripheral axonal course from sensory cell to spiral ganglion. Analysis of intracellularly labeled auditory-nerve fibers shows that peripheral axons and cell bodies of low- and medium-SR fibers tend to be found closer to scala vestibuli than high-SR fibers. Since low- and medium-SR fibers tend to be thinner, this SR-based segregation can also be demonstrated as a fiber-caliber gradient in the osseous spiral lamina. The issue of SR-based spatial segregation is relevant to reports that ganglion cells near scala vestibuli project to different regions of the cochlear nucleus than cells near scala tympani (Leake and Snyder, '89, J. Comp. Neurol. 281:612-629). Combining the results of the two studies suggests that there may be some SR-based spatial segregation of inputs to the cochlear nucleus.

Animals↗
PubMed1984

Immunocytochemical localization of glutaminase-like immunoreactivity in the auditory nerve.

The immunocytochemical localization of glutaminase, which we have proposed as a marker for excitatory amino acid neurotransmitters was determined in the guinea pig auditory nerve. Glutaminase-like immunoreactivity was seen in auditory nerve terminals in the cochlear nucleus and in the cell bodies of the auditory nerve in the cochlea. This staining was seen in type I and not type II spiral ganglion cells. Glutaminase-like immunoreactivity was also observed in granule cells in the cochlear nucleus.

Animals↗
PubMed1980

Suppression of the auditory frequency following response during visual attention.

Frequency-following responses (FFRs) were recorded from unanesthetized cats with electrodes chronically implanted in the cochlear nucleus and on the round window. Tone bursts of different frequencies (irrelevant stimuli) were presented repetitively (85 dB SPL, 1/sec) as background before, during, and after the presentation of a visual discrimination task (relevant stimuli) which attempted to alter the attentive state of the animals. The mean peak-to-peak amplitudes of the FFRs from the cochlear nucleus were significantly reduced in amplitude during attention to the visual discrimination stimuli when compared with the amplitudes of the pretest- and posttest-control periods. However, at the round window (cochlear microphonic) no significant differences in amplitude were observed for the same periods. Although the amplitudes of the FFRs were reduced in amplitude at all frequencies during visual attention, much greater suppression occurred at the middle frequencies (700-2000 Hz) than at higher or lower frequencies. These data suggest that during visual attention the FFRs are attenuated by a central inhibitory mechanism.

Animals↗
PubMed1991

Neuronal activity and tonotopy in the auditory system visualized by c-fos gene expression.

Responsiveness in the cochlear nucleus complex and inferior colliculus of the mouse to tonal stimulation is labelled via immunocytochemically stained Fos protein that is expressed by c-fos gene activation in excited neurons. The locations of Fos-positive neurons closely reproduce the tonotopic maps in the dorsal cochlear nucleus and inferior colliculus. Thus, the c-fos method can demonstrate stimulus-related local neuronal activation on a single-cell level and may be useful to complement other mapping techniques such as electrophysiological recording or 2-deoxyglucose autoradiography.

Acoustic Stimulation↗
PubMedDate not supplied

Induction of audiogenic seizures in normal and genetically epilepsy-prone rats following focal microinjection of an excitant amino acid into reticular formation and auditory nuclei.

An excitant amino acid (EAA), N-methyl-D-aspartate (NMDA), induces susceptibility to seizures when bilaterally microinjected into subcortical auditory nuclei of normal rats. Thirty-five percent of animals exhibit only audiogenic seizures (AGS) after infusions of NMDA into inferior colliculus (IC). Infusions into cochlear nucleus and medial geniculate body never produce susceptibility to AGS without non-audiogenic seizures (N-AGS). The overall seizure incidence (AGS and N-AGS) with IC infusions is 100%, but the incidence is less than 50% with infusions into cochlear nucleus or medial geniculate body. Although AGS susceptibility is induced by NMDA infusions in normal animals, the seizures are submaximal in severity and lack tonic components. Bilateral infusions of NMDA into IC or reticular formation of the substrain of genetically epilepsy-prone rats (GEPRs) that exhibits submaximal AGS (GEPR-3s) do not increase seizure severity. These data along with studies showing increased EAA levels and excitotoxic-like damage in the IC of the GEPR and blockade of AGS with an EAA receptor antagonist or synthesis inhibitor suggest that an EAA in the IC is involved in initiation of AGS in the GEPR. However, EAA action in the GEPR IC is not sufficient to induce the complete spectrum of seizure behaviors, and additional mechanisms may be required for induction of maximal severity audiogenic seizures.

Acoustic Stimulation↗
PubMed2002

Speech perception using maps based on neural response telemetry measures.

OBJECTIVE: To determine how speech perception is affected for Nucleus cochlear implant users when their speech processor is programmed using neural response telemetry (NRT) measures rather than traditional behavioral estimates of threshold and maximum comfort level. DESIGN: Electrically evoked compound action potential (EAP) thresholds were measured for a group of 10 adult Nucleus cochlear implant users. These physiologic threshold estimates were used to create three SPEAK MAPs. One MAP ("+10/-20 MAP") was created using only the NRT data. The second MAP ("Combined MAP") was created using a combination of both EAP thresholds and a single behavioralmeasure of threshold and maximum comfort level from electrode 10. A third MAP ("Measured MAP") was created using standard programming techniques. Speech perception was then assessed using each of these three MAPs for either CUNY or HINT sentences presented at two different presentation levels (70 dB SPL and 55 dB SPL). RESULTS: On average, at the higher presentation level (70 dB SPL) subjects performed significantly better when using the Measured MAP than whenusing either of the NRT-based MAPs. No significant difference in speech perception was obtained for either of the three MAPs when the lower presentation level (55 dB SPL) was used. CONCLUSION: This study demonstrated that at relatively high presentation levels, speech perception scores obtained by subjects who use MAPs based solely or primarily on EAP thresholds ar eslightly lower than similar scores obtained using a more traditional MAP. This difference did not reach statistical significance at lower presentation levels. We interpret these findings in a positive light to suggest that although NRT-based MAPs may not be optimal, they are of sufficient quality to support reasonable levels of speech understanding. This is important to establish because these MAPs may prove to be most useful when very young children receive a cochlear implant.

Brain↗
PubMed2004

Performance of subjects fit with the Advanced Bionics CII and Nucleus 3G cochlear implant devices.

OBJECTIVE: To determine if subjects who used different cochlear implant devices and who were matched on consonant-vowel-consonant (CNC) identification in quiet would show differences in performance on speech-based tests of spectral and temporal resolution, speech understanding in noise, or speech understanding at low sound levels. DESIGN: The performance of 15 subjects fit with the CII Bionic Ear System (CII Bionic Ear behind-the-ear speech processor with the Hi-Resolution sound processing strategy; Advanced Bionics Corporation) was compared with the performance of 15 subjects fit with the Nucleus 24 electrode array and ESPrit 3G behind-the-ear speech processor with the advanced combination encoder speech coding strategy (cochlear corporation). SUBJECTS: Thirty adults with late-onset deafness and above-average speech perception abilities who used cochlear implants. MAIN OUTCOME MEASURES: Vowel recognition, consonant recognition, sentences in quiet (74, 64, and 54 dB SPL [sound pressure level]) and in noise (+10 and +5 dB SNR [signal-to-noise ratio]), voice discrimination, and melody recognition. RESULTS: Group differences in performance were significant in 4 conditions: vowel identification, difficult sentence material at +5 dB and +10 dB SNR, and a measure that quantified performance in noise and low input levels relative to performance in quiet. CONCLUSIONS: We have identified tasks on which there are between-group differences in performance for subjects matched on CNC word scores in quiet. We suspect that the differences in performance are due to differences in signal processing. Our next goal is to uncover the signal processing attributes of the speech processors that are responsible for the differences in performance.

Adult↗
PubMedDate not supplied

Carcinomatous encephalomyelitis with auditory and vestibular manifestations.

A clinical and pathological study of carcinomatous encephalomyelitis is presented. Attention is drawn to the various types of nonmetastatic paraneoplastic syndromes and their particular association with oat cell carcinoma of the lung. The feature of special interest in this study is the onset with otologic symptoms, sudden deafness in the left ear and vertigo, at a time when the neoplastic basis for the disease was not clinically evident. The most striking change in the left temporal bone is the almost total loss of cochlear neurons in Rosenthal's canal and degeneration of both divisions of the vestibular nerve. The organ of Corti and stria vascularis are normal throughout the cochlear duct. The vestibular sense organs are normal. The left cochlear nucleus is devoid of neurons, this neuronal loss is accompanied by a well developed astrocytic and microglial response similar to that in the medulla and spinal cord. This represents a carcinomatous sensory neuropathy involving the left VIII nerve with simultaneous involvement of the left cochlear nucleus. The pathogenesis of this condition still defies explanation, but there are some insights in the autoimmune sector.

Carcinoma, Small Cell↗
PubMed1997

Evaluating the plasticity potential of the auditory brain stem nucleus in the rat.

OBJECTIVE: To study the adaptation of the auditory brainstem to auditory loss. STUDY DESIGN: Growth-associated protein 43 (GAP-43) immunoreactivity was studied in in rats whose cochleas had been removed. RESULTS AND DISCUSSION: Neurons in the lateral superior olive were found to synthesize GAP-43 in a pattern that paralleled the changes in GAP-43 immunoreactivity in the cochlear nucleus after cochlear ablation. These findings suggest that new patterns of synaptic communication can be established after damage to the cochlea.

Animals↗
PubMed1990

The Purkinje cell class may extend beyond the cerebellum.

The cerebellum develops from a germinal zone at the rhombic lip of the metencephalon. This region, like the telencephalic vesicle which gives rise to the cerebral cortex, presumably consists of germinative units showing a rather repetitive neurogenetic pattern. In all cerebellar folia, cortical neurons, and especially the Purkinje cells, express highly stereotyped phenotypes, although some variations in their chemical make-up have been uncovered with monoclonal antibodies. Here, we demonstrate for the first time that three independent murine mutations, Lurcher, Purkinje cell degeneration and staggerer, which result in the postnatal degeneration of Purkinje cells, also cause the elimination of cartwheel cells of the dorsal cochlear nucleus. The cerebellar granule cell mutation, weaver, which spares most Purkinje cells in the lateral cerebellum, also spares cartwheel cells. These data support the notion that the cerebellar germinative zone extends to the caudal portion of the rhombic lip, which gives rise to the dorsal cochlear nucleus.

Animals↗
PubMed1996

Organization of ventrolateral periolivary cells of the cat superior olive as revealed by PEP-19 immunocytochemistry and Nissl stain.

Ventrolateral periolivary cell groups, through their descending projections to the cochlear nucleus (CN) and local projections to principal nuclei of the superior olive, may participate in brainstem mechanisms mediating such tasks as signal detection in noisy environments and sound localization. Understanding the function of these cell groups can be improved by increased knowledge of the organization of their synaptic inputs in relation to their cellular characteristics. Immunocytochemistry for PEP-19 (a putative calcium binding protein) reveals four patterns of immunolabeling within the ventrolateral periolivary region. Three of the patterns, which have distinct fiber and punctate labeling characteristics, help to define three subdivisions of the lateral nucleus of the trapezoid body (LNTB). The fourth pattern defines two other nuclei, the anterolateral periolivary nucleus (rostral) and the posterior periolivary nucleus (caudal), which display many immunoreactive cell bodies but little fiber and punctate labeling. One of the subdivisions of the LNTB contains large PEP-19 immunolabeled puncta arranged in pericellular nests. Analysis of Nissl-stained sections reveals a neuronal population that resembles globular cells of the ventral cochlear nucleus (VCN) and which colocalizes with pericellular nests of large immunolabeled puncta. Cell counts reveal that roughly 10,000 neurons constitute the cat ventrolateral periolivary region, 9,000 of which are found in the LNTB. Three-dimensional reconstructions of auditory brainstem nuclei clarify the complex spatial relationships among these structures.

Animals↗