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At least 559 records · Page 31Linked to original sources
PubMed2001

Electrophysiological measures of auditory function in the neurofilament-deficient mutant quail (Quv).

Auditory pathway electrophysiological studies were performed on the mutant quail 'Quv'. This mutation is known to result in neurofilament deficiencies of both the peripheral and central nervous systems. Auditory evoked brainstem responses (ABRs), electrocochleograms (EcochGs) and middle latency responses (MLRs) were evaluated. ABRs in Quv quails demonstrated markedly altered waveforms exhibiting longer latencies, absence of the later peaks and lower amplitudes. The EcochG showed normal cochlear microphonics with no obvious abnormalities in amplitude or latency and normal latencies for peak N1. Quv quails had a mild threshold elevation with a normal latency for the first peak of the ABR (P1). The Quv MLRs showed no significant differences in amplitude but they revealed a latency prolongation for peaks N0, Pa and Na relative to the controls. We have discovered abnormal findings of auditory evoked potentials in the neurofilament-deficient quail (Quv). We suggest that the smaller axonal size and axonal hypotrophy due to altered neurofilament expression underlies these abnormal auditory evoked potential responses.

Acoustic Stimulation↗
PubMed1992

[Therapy of sensorineural hearing loss in the aged with arteriosclerotic disease: a comparison of hydroxyethyl starch and prostaglandin].

We assessed 42 patients (aged between 51 and 86 years, average age: 71.6 years) with chronic bilateral sensorineural hearing loss in old-age, who showed bilateral pathological loss of discrimination. This was a group of patients diagnosed with internal-angiological arteriosclerotic vascular disease (uni- or bilateral obliteration of the carotid artery, condition following a cerebral ischaemic attack or peripheral arterial occlusive disease). 21 patients received infusion treatment with hydroxyethylamylum (HAES-steril 10%), a further 21 patients were infused with prostaglandin (Prostavasin, PGE-1) for three weeks. Pure tone audiometric and speech audiometric assessments were carried out before and after the infusion treatment (minimal loss of discrimination, overall word discrimination). It was statistically shown that there was no significant improvement of the average auditory threshold between 0.5 and 8 kHz using hydroxyethylamylum and prostaglandin. However, the examination results verify an increase of the minimal loss of discrimination and an improvement of speech comprehension following therapy with hydroxyethylamylum and prostaglandin. Between these two substances no difference was to be proved statistically. Our therapeutic results can be explained by the following considerations: 1. An improved circulation of the inner ear and the auditory pathway is to be regarded as possible reason for the achievement of the therapeutic effect. 2. An influence on the transmitter system of the cochlea and the auditory pathway is conceivable.

Aged↗
PubMed1987

Evidence for parallel processing in the frog's auditory thalamus.

We have conducted anatomical and physiological experiments to investigate the functional organization of the dorsal thalamus in the northern leopard frog (Rana pipiens pipiens). Our studies provide evidence for parallel auditory processing at this level of the frog's brain. Acoustically evoked potentials were recorded from the posterior and central thalamic nuclei and several differences in sound-evoked activity were noted between them: the amplitude of acoustically evoked potentials (AEPs), in response to a standard search stimulus, was always greater in the central, as opposed to the posterior, nucleus; the posterior, but not central, nucleus exhibited the phenomenon of nonlinear summation when 350-Hz and 1,700-Hz tones were presented simultaneously rather than individually; and the central, but not posterior, nucleus showed selectivity for the repetition rate of pulsed sound signals. The posterior and central thalamic nuclei also possessed distinct innervation patterns as revealed by the HRP transport patterns arising from these structures. The central nucleus was reciprocally connected with the major auditory relay stations along the frog's central auditory pathway including the superior olive, nucleus of the lateral lemniscus, and the torus semicircularis. Major projections to the lateral thalamic nucleus, ventral hypothalamus, and the telencephalic striatal complex were also observed. The posterior nucleus, on the other hand, established reciprocal connections primarily with the medial reticular nucleus, ventral midbrain tegmentum, and structures constituting of the ventral thalamic nuclei, particularly the nucleus of Bellonci. Thus, time and frequency cues contained within the species mating call, and conveying information concerning species identity, appear to be processed independently within the frog's thalamus with separate neural channels for each.

Animals↗
PubMed1999

Audiological assessment in patients with mitochondrial myopathy.

Mitochondrial myopathies comprise a heterogeneous group of disorders characterized by the presence of ragged red fibres in muscle biopsy. The present study investigates the audiological features in a group of 14 patients in whom diagnosis was histologically confirmed. A complete ENT, neurological and audiological work-up was performed for every patient, including measurement of brainstem auditory evoked potentials (BAEPs). Most patients presented with a varying degree of hearing loss and occasional abnormalities of the latencies and interpeak latencies of the BAEPs, but only the increased latencies of waves I and V have been statistically confirmed. Audiological data suggest non-specific involvement at one or more sites along the auditory pathway.

Adult↗
PubMed2002

Instructed learning in the auditory localization pathway of the barn owl.

A bird sings and you turn to look at it a process so automatic it seems simple. But is it? Our ability to localize the source of a sound relies on complex neural computations that translate auditory localization cues into representations of space. In barn owls, the visual system is important in teaching the auditory system how to translate cues. This example of instructed plasticity is highly quantifiable and demonstrates mechanisms and principles of learning that may be used widely throughout the central nervous system.

Aging↗
PubMed2004

Song-induced gene expression: a window on song auditory processing and perception.

We review here evidence that a large portion of the caudomedial telencephalon of songbirds, distinct from the song control circuit, is involved in the perceptual processing of birdsong. When songbirds hear song, a number of caudomedial pallial areas are activated, as revealed by expression of the activity-dependent gene zenk. These areas, which include field L subfields L1 and L3, as well as the adjacent caudomedial nidopallium (NCM) and caudomedial mesopallium (CMM), are part of the central auditory pathway and constitute a lobule in the caudomedial aspect of the telencephalon. Several lines of evidence indicate that the neural circuits integrating this lobule are capable of performing the auditory processing of song based on fine acoustic features. Thus, this lobule is well positioned to mediate song perceptual processing and discrimination, which are required for vocal communication and vocal learning. Importantly, the zenk gene encodes a transcription factor linked to synaptic plasticity, and it regulates the expression of target genes associated with specific neuronal cell functions. The induction of zenk likely represents a key regulatory event in a gene cascade triggered by song and leading to neuronal plasticity. Thus, zenk may be linked to molecular and cellular mechanisms underlying experience-dependent modification of song-responsive circuits. In summary, songbirds possess an elaborate system for song perceptual processing and discrimination that potentially also subserves song-induced neuronal plasticity and song memory formation. The continued use of a multidisciplinary approach that integrates molecular, anatomical, physiological and behavioral methodologies has the potential to provide further significant insights into the underlying neurobiology of the perceptual aspects of vocal communication and learning.

Animals↗
PubMed1994

Site of auditory plasticity in the brain stem (VLVp) of the owl revealed by early monaural occlusion.

1. The optic tectum of the barn owl contains a physiological map of interaural level difference (ILD) that underlies, in part, its map of auditory space. Monaural occlusion shifts the range of ILDs experienced by an animal and alters the correspondence of ILDs with source locations. Chronic monaural occlusion during development induces an adaptive shift in the tectal ILD map that compensates for the effects of the earplug. The data presented in this study indicate that one site of plasticity underlying this adaptive adjustment is in the posterior division of the ventral nucleus of the lateral lemniscus (VLVp), the first site of ILD comparison in the auditory pathway. 2. Single and multiple unit sites were recorded in the optic tecta and VLVps of ketamine-anesthetized owls. The owls were raised from 4 wk of age with one ear occluded with an earplug. Auditory testing, using digitally synthesized dichotic stimuli, was carried out 8-16 wk later with the earplug removed. The adaptive adjustment in ILD coding in each bird was quantified as the shift from normal ILD tuning measured in the optic tectum. Evidence of adaptive adjustment in the VLVp was based on statistical differences between the VLVp's ipsilateral and contralateral to the occluded ear in the sensitivity of units to excitatory-ear and inhibitory-ear stimulation. 3. The balance of excitatory to inhibitory influences on VLVp units was shifted in the adaptive direction in six out of eight owls. In three of these owls, adaptive differences in inhibition, but not in excitation, were found. For this group of owls, the patterns of response properties across the two VLVps can only be accounted for by plasticity in the VLVp. For the other three owls, the possibility that the difference between the two VLVps resulted from damage to one of the VLVps could not be eliminated, and for one of these, plasticity at a more peripheral site (in the cochlea or cochlear nucleus) could also explain the data. In the remaining two owls, there was no evidence of adaptive adjustment in the VLVp despite large adaptive adjustments in the optic tectum. 4. The adjustment of ILD coding in the VLVp was always substantially smaller than expected based on the adjustment of ILD tuning in the optic tectum measured in the same animals. This indicates the involvement of at least one additional site of adaptive plasticity in the auditory pathway above the level of the VLVp.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1979

Functional organization of some auditory nuclei in the guinea fowl demonstrated by the 2-deoxyglucose technique.

The auditory pathway of the Guinea Fowl was labeled with [C14]2-deoxy-D-glucose after stimulation with pure tones, harmonic tones and species-specific calls. In addition to other auditory nuclei, which showed more or less uniform labeling with the present technique, the n. mesencephalicus lateralis dorsalis (MLD) of the midbrain, as well as field L and parts of the hyperstriatum ventrale in the telencephalon, showed a stripe-pattern of labeling after stimulation with a pure tone. The position and orientation of the tone-activated striped areas in field L, observed after stimulation with different tones, correspond to isofrequency contours obtained with microelectrode recordings. The labeling of the three congruent tonotopically organized layers of field L (L1, L2, and L3) was not uniform along the anterior-posterior axis of the field. Harmonic tones produced multiple reactive stripes each of which corresponded to the stripe characteristic of a particular harmonic presented as a pure tone. The species-specific Iambus-call labeled the tonotopic area of field L that corresponds to the frequency band with the highest energy of the call. The hyperstriatum ventrale generally showed a weaker pattern of labeling that, however, resembled the labeling in field L.

Animal Communication↗
PubMed2002

Diagnostic imaging in clinical neuro-otology.

Advances in magnetic resonance imaging and computed tomography have made a more detailed imaging of the inner ear possible, and magnetic resonance imaging also allows the evaluation of the auditory pathways inside the brainstem. This has led to new possibilities in patients with congenital deafness, cochlear implant candidates, patients with inner ear infection, Tullio phenomenon, acoustic schwannomas and lesions along the auditory pathway, which have been described recently. New animal studies, which have evaluated intracochlear enhancement, encourage radiologists and neuro-otologists to push magnetic resonance imaging techniques even further than the already amazing possibilities that they offer.

Deafness↗
PubMed1998

Auditory cortical responses in hearing subjects and unilateral deaf patients as detected by functional magnetic resonance imaging.

Functional magnetic resonance imaging is a non-invasive method for the detection of focal brain activity at high spatial resolution. Acoustic stimulation leads to a blood oxygenation level dependent signal change in the plane of the superior temporal gyrus. The dependence of this response in the auditory cortex on binaural, monaural left and monaural right acoustic stimulation for 10 healthy subjects and five monaural deaf patients is described. Acoustic stimulation consists of 1000 Hz pulsed sine tones at a pulse rate of 6 Hz and a sound pressure level of 95 dB. For monaural stimulation, normal-hearing subjects revealed a strong lateralization of cortical response towards the contralateral hemisphere. The lateralization ratios between left and right hemispheric response areas were 3.4-5.2 for monaural stimulation and nearly balanced for binaural stimulation. Additionally, the sum of cortical activation volumes induced by monaural left and right stimulation was approximately 30% smaller than for binaural stimulation, indicating either inhibitory mechanisms or neuronal facilitation within the auditory pathways. For monaural deaf subjects the lateralization ratio between left to right response was just 1.3 towards the contralateral hemisphere of the healthy ear, which is comparable to binaural responses of normal-hearing subjects. This observation seems to indicate a plasticity or a reorganization of auditory pathways of monaural deaf patients.

Adult↗
PubMed2003

Snake bioacoustics: toward a richer understanding of the behavioral ecology of snakes.

Snakes are frequently described in both popular and technical literature as either deaf or able to perceive only groundborne vibrations. Physiological studies have shown that snakes are actually most sensitive to airborne vibrations. Snakes are able to detect both airborne and groundborne vibrations using their body surface (termed somatic hearing) as well as from their inner ears. The central auditory pathways for these two modes of "hearing" remain unknown. Recent experimental evidence has shown that snakes can respond behaviorally to both airborne and groundborne vibrations. The ability of snakes to contextualize the sounds and respond with consistent predatory or defensive behaviors suggests that auditory stimuli may play a larger role in the behavioral ecology of snakes than was previously realized. Snakes produce sounds in a variety of ways, and there appear to be multiple acoustic Batesian mimicry complexes among snakes. Analyses of the proclivity for sound production and the acoustics of the sounds produced within a habitat or phylogeny specific context may provide insights into the behavioral ecology of snakes. The relatively low information content in the sounds produced by snakes suggests that these sounds are not suitable for intraspecific communication. Nevertheless, given the diversity of habitats in which snakes are found, and their dual auditory pathways, some form of intraspecific acoustic communication may exist in some species.

Acoustics↗
PubMedDate not supplied

Hearing loss of a central type secondary to anoxic anoxia.

The effect of anoxic anoxia on the threshold sensitivity and amplitude of the responses from the auditory cortex, inferior colliculus and cochlea to acoustic stimuli in guinea pigs was studied. Decay of the amplitude of the responses from the auditory cortex and the inferior colliculus occurs faster and is more severe than that of the cochlea. Recovery of the amplitude of the responses is slower at the auditory cortex and the inferior colliculus than at the cochlea. Loss of auditory threshold sensitivity in anoxic anoxia is most prominent at the auditory cortex. The loss of sensitivity at the inferior colliculus is the next most severe. The loss of sensitivity at the cochlea is negligible. The relative vulnerability of the central auditory pathway to anoxic anoxia as compared to the end organ is demonstrated.

Animals↗
PubMed1994

Postoperative changes in the contralateral auditory brainstem response after microvascular decompression in cases of trigeminal neuralgia.

Postoperative changes in auditory brainstem response (ABR) in 40 patients with trigeminal neuralgia (TN) who underwent microvascular decompression (MVD) were analyzed. A high proportion (60%) were found to have a decrease in the latency of wave V in the contralateral (unaffected) ABR in the postoperative period. In some cases, a decrease in the latency of wave V was found on the unaffected side postoperatively while an increase was found on the affected side. Furthermore, in one case it was found that an improvement of the shortened latency of wave V on the unaffected side occurred in parallel with a recovery of prolonged latency on the affected side. This indicates that the decrease in the latency of wave V on the unaffected side corresponds to some retrocochlear lesion produced by MVD on the affected side, and shortened latency is considered to be a result of damage to the efferent system of the auditory pathway.

Adult↗
PubMedDate not supplied

Neurophysiological basis of discrimination of speech sounds.

The present paper discusses the information processing in the auditory nervous system with particular reference to speech sounds. The main emphasis is laid upon results of recordings from single nerve cells in the ascending auditory pathway and hypothesis about processing of speech-like sounds are put forward on the basis of these results.

Auditory Pathways↗
PubMed1997

[Influence of hypoxia on the human auditory system].

The present paper presents a review of the literature on "hypoxia and human auditory mechanisms". It examines and discusses, above all, the results obtained in the various studies using pure tone audiometry and auditory evoked potentials. At the present time, the two areas which appear most sensitive to hypoxia are the cochlea and, above all, the telencephalic auditory cortex (specifically those sectors dedicated to cognitive processing of auditory stimulation). However, many other areas which are sensitive to hypoxia, but to a lesser extent, have also been identified, even in other sectors of the auditory pathway. Particularly worthy of note is the effectiveness of the metabolic compensatory mechanisms which come into play upon hypoxic stress. These mechanisms include vasodilation and the presence of metabolic reservoirs. Nevertheless, there are still a number of open questions regarding how the auditory pathway functions in the case of hypoxia; thus the experimental study of hypoxic hypoxia is still an interesting, fruitful research field in audiology.

Auditory Cortex↗
PubMed2004

Reduced auditory efferent activity in childhood selective mutism.

BACKGROUND: Selective mutism is a psychiatric disorder of childhood characterized by consistent inability to speak in specific situations despite the ability to speak normally in others. The objective of this study was to test whether reduced auditory efferent activity, which may have direct bearings on speaking behavior, is compromised in selectively mute children. METHODS: Participants were 16 children with selective mutism and 16 normally developing control children matched for age and gender. All children were tested for pure-tone audiometry, speech reception thresholds, speech discrimination, middle-ear acoustic reflex thresholds and decay function, transient evoked otoacoustic emission, suppression of transient evoked otoacoustic emission, and auditory brainstem response. RESULTS: Compared with control children, selectively mute children displayed specific deficiencies in auditory efferent activity. These aberrations in efferent activity appear along with normal pure-tone and speech audiometry and normal brainstem transmission as indicated by auditory brainstem response latencies. CONCLUSIONS: The diminished auditory efferent activity detected in some children with SM may result in desensitization of their auditory pathways by self-vocalization and in reduced control of masking and distortion of incoming speech sounds. These children may gradually learn to restrict vocalization to the minimal amount possible in contexts that require complex auditory processing.

Acoustic Impedance Tests↗
PubMed1998

Metabotropic glutamate receptor activation modulates sound level processing in the cochlear nucleus.

The principal role of ionotropic glutamate receptors in the transmission and processing of information in the auditory pathway has been investigated extensively. In contrast, little is known about the functional contribution of the G-protein-coupled metabotropic glutamate receptors (mGluRs), although their anatomic location suggests that they exercise a significant influence on auditory processing. To investigate this issue, sound-evoked responses were obtained from single auditory neurons in the cochlear nuclear complex of anesthetized cats and gerbils, and metabotropic ligands were administered locally through microionophoretic pipettes. In general, microionophoresis of the mGluR agonists, (1S, 3R)-1-aminocyclopentane-1,3-dicarboxylic acid or (2S,1'S, 2'S)-2-(carboxycyclopropyl)glycine, initially produced a gradual increase in spontaneous and sound-evoked discharge rates. However, activation and recovery times were significantly longer than those observed for ionotropic agonists, such as N-methyl--aspartate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, consistent with the recruitment of a second-messenger system. The efficacy of mGluR agonists was diminished after administration of the mGluR antagonist, (+)-alpha-methyl-4-carboxyphenylglycine, consistent with a selective action at metabotropic recognition sites. In contrast, two distinct changes were observed after the mGluR agonist had been discontinued for several minutes. Approximately 50% of neurons exhibited a chronic depression of sound-evoked discharge rate reminiscent of long-term depression, a cellular property observed in other systems. Approximately 30% of neurons exhibited a long-lasting enhancement of the sound-evoked response similar to the cellular phenomenon of long-term potentiation. These findings suggest that mGluR activation has a profound influence on the gain of primary afferent driven activity in the caudal cochlear nucleus.

Acoustic Stimulation↗
PubMed1997

Auditory development of the hearing child.

Auditory perception is defined, here, as the interpretation of sensory evidence, derived from sound, in terms of the objects and events that caused the sound. Like other kinds of perception, it involves the use, not only of sensory evidence, but also of contextual evidence, prior knowledge, memory, attention, and processing skills. Auditory speech perception is special because the events to be perceived are those of language. Similarly, the listener's knowledge base and processing skills must include those related to language in general, and spoken language in particular. The auditory system is complete and functional at birth but myelination continues for several years in the higher auditory pathways. This pattern of anatomical maturation is reflected in electrophysiological responses. Similarly, infants display sophisticated discrimination and recognition ability but psychoacoustic performance does not reach adult levels for several years. Empirical data on the development of auditory processing are sparse, but much work has been done on auditory speech perception. Infants at 6 months demonstrate the beginnings of phonemic classification, and performance improves during childhood in a variety of areas. These include: phonetic contrast perception, phoneme recognition, perception of speech in noise, selective attention, and the use of linguistic context. Experience obviously plays a key role in the development of the knowledge and skills required for auditory perception in general and auditory speech perception in particular. It is tempting to assume that the sensory evidence available to the developing child is determined only by the functional integrity of the peripheral auditory system, independent of auditory experience. There is, however, increasing evidence in animals of the influence of auditory experience on the organization of the auditory pathways. Such organization could increase the sensory evidence made available from patterns of neural excitation produced in the cochlea.

Adolescent↗