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Results for “Auditory Pathways”

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At least 73 records · Page 4Linked to original sources

PubMed1999

Central electrical stimulation of the auditory pathway in neurofibromatosis type 2.

The auditory brainstem implant (ABI) is a viable treatment option for patients with neurofibromatosis type 2 (NF2) whom either vestibular schwannomas or the surgery used to remove them has rendered totally deaf. This device stimulates the central auditory pathways in a manner similar to the cochlear implant in individuals with a total hearing loss. A multichannel model with transcutaneous signal transmission is in use experimentally in both the United States and Europe. Of 14 patients implanted with the ABI in a European pilot study, 13 received auditory sensations at initial tuning. Surgical implantation of the ABI is generally, but not always, performed at the same time as tumor removal, with the preferred route being the transmastoid-translabyrinthine approach. After insertion, monitoring of the device is required to optimize the location of its electrode on the cochlear nucleus complex.

Electric Stimulation↗

PubMed1992

Frequency selectivity is related to temporal processing in parallel thalamocortical auditory pathways.

Lemniscal and non-lemniscal parallel thalamocortical auditory pathways have been identified with the ventral medial geniculate body (MGB) vs. the dorsal and medial MGB, respectively. Lemniscal neurons have narrow frequency tuning and provide highly specific frequency information to the auditory cortex whereas non-lemniscal neurons generally have broader tuning and greater response lability, including plasticity of frequency receptive fields during learning. To determine if frequency selectivity is related to temporal fidelity of response, we measured both the breadth of tuning and neuronal excitability in a paired tone paradigm for single neurons throughout the MGB. Excitability to the second tone of a pair was directly correlated with frequency selectivity: the narrower the frequency tuning, the greater the excitability. Cells with broad tuning based on multiple-peak response areas also were less excitable than cells with single-peak RAs. Cells in the ventral MGB showed greater temporal fidelity of response (greater excitability) than cells in the dorsal and medial MGB. These findings show that high degrees of both frequency selectivity and temporal response fidelity are characteristic of the lemniscal, but not the non-lemniscal, thalamocortical auditory system.

Acoustic Stimulation↗

PubMed1992

Development of the brainstem auditory pathway in low birthweight and perinatally asphyxiated children with neurological sequelae.

Low birthweight (LBW) and perinatal asphyxia are known to be high-risk factors for a number of neurodevelopmental deficits. In this study, we analyzed brainstem auditory evoked response (BAER) in 18 LBW and 36 perinatally asphyxiated children with non-progressive neurological sequelae after the age of 6 months to inspect and compare the long-term influence of LBW and perinatal asphyxia on the brainstem auditory pathway. The typical changes in the BAER of children born with LBW were slightly shorter III-V interpeak interval and smaller III-V/I-III interval ratio than normal controls. On the contrary, the abnormalities in the BAER of 36 children surviving perinatal asphyxia were characterized by a reduction of the amplitude of wave V with normal intervals. This discrepancy in the BAER between the children born with LBW and those with perinatal asphyxia implies that the two high-risk factors exert different long-term influences on the development of the brainstem auditory pathway. It is hypothesized that these characteristic changes may be indicative of a major influence of LBW on the generators contributing to wave III and that of asphyxia on the generators contributing to wave V. An increase in response threshold with abnormal latency-intensity function was found in 11% of the LBW children and 19% of the asphyxiated children, suggesting that sensorineural hearing impairment occurred more frequently in children surviving perinatal asphyxia than in those born with LBW. Follow-up study demonstrates that the abnormalities in the brainstem auditory pathway of LBW and asphyxiated children after the age of 6 months is likely to be persistent.

Asphyxia Neonatorum↗

PubMed1984

Effects of alcohol on functional development of the auditory pathway in the brainstem of infants and chick embryos.

The effects of alcohol on the development of neural function in the auditory pathway of the brainstem have been examined in human neonates and chick embryos. Auditory brainstem evoked responses were recorded in six infants of mothers for whom there was evidence of alcohol abuse during pregnancy. In four of the infants, evoked responses were abnormal, with poorly defined, inconsistent peaks. Neurophysiological and histological studies were done on chick embryos which received a single dose of alcohol early incubation. In most surviving embryos the neuroanatomical arrangement of the auditory nuclei in the brainstem was normal. However, Golgi impregnation revealed abnormalities in the length and structure of the dendrites in nucleus laminaris. Electrically evoked neuronal activity revealed abnormalities of synaptic function and the distribution of nerve terminals. The results indicate that in infants and chick embryos the functional development of the auditory pathway in the brainstem is disrupted by exposure to alcohol. Such early changes in this sensory pathway may contribute to the behavioural and intellectual handicaps associated with the fetal alcohol syndrome.

Action Potentials↗

PubMed2002

Hearing loss in early infancy affects maturation of the auditory pathway.

The influence of early cochlear hearing loss on maturation of the auditory pathway was studied by measuring auditory brainstem responses (ABR). In a retrospective study, 85 children with normal hearing (46 males, 39 females; age range 2 months to 14 years) and 165 children with binaural cochlear hearing impairment (89 males, 76 females; age range 1 month to 16 years) were examined. A significant positive correlation (p<0.001) between the degree of hearing loss and interpeak latencies I-V (IPL(I-V)) of the ABR was observed. No significant correlation (p=0.85) was found between hearing loss and interpeak latencies I-III (IPL(I-III)). These findings can be interpreted as indicating a marked delay in maturation of higher brainstem structures due to reduced auditory input during infancy. The correlation differs notably from results of comparable studies of adults published in recent literature. This leads to the assumption that the developing human brain is particularly sensitive to auditory deprivation. Thus, our results indicate the importance of a normal acoustic environment during sensitive periods in early childhood to ensure normal hearing and speech development.

Adolescent↗

PubMedDate not supplied

Deafness-induced changes in the auditory pathway: implications for cochlear implants.

A profound sensorineural hearing loss induces significant pathological and atrophic changes within the cochlea and central auditory pathway. We describe these deafness-induced morphological and functional changes following controlled lesions of the cochlea in experimental animals. Such changes are generally consistent with the limited number of reports describing deafness-induced changes observed in human material. The implications of these pathophysiological changes within the auditory pathway on cochlear implant function are discussed. Finally, the plastic response of the deafened auditory system to electrical stimulation of the auditory nerve is reviewed in light of the clinical implications for cochlear implant recipients.

Animals↗

PubMed1982

Some aspects of the auditory pathway and audition in the European mole, Talpa europaea.

The structure of the lower auditory pathway and certain responses to sounds were studied in the European mole (Talpa europaea). While the animal possesses a structurally normal cochlear nuclear complex and auditory midbrain, the medial superior olive, although small, is prominent and the lateral superior olive is lacking. This characteristic has been observed in other species with essentially low frequency hearing. Behavioural and electrophysiological responses to sound were evoked between 0.1 and 15 kHz, and moles were apparently at least sensitive to tones of 5-8 kHz as they were to low tones. In general, evidence is presented for the mole having essentially normal mammalian auditory characteristics.

Acoustic Stimulation↗

PubMed1985

Functioning of the brain-stem auditory pathway in non-retarded autistic individuals.

Functioning of auditory brain-stem pathways was examined in non-retarded autistic individuals (14-28 years of age). Functioning was assessed by recording ERPs (event-related brain potentials) generated by these auditory pathways. These ERPs were evoked by click stimuli and occurred within the first 8 msec following the onset of the click. To assess the ability of these early auditory pathways to process sensory stimuli of varying characteristics, we systematically varied click intensity, rate of stimulation, ear of stimulation, and polarity of clicks. The results show that non-retarded autistic individuals have normal functioning of the brain-stem auditory pathways which generate these ERPs: every autistic subject had normal ERPs. So, disorder in auditory brain-stem pathways which generate these ERPs is not necessary for autism to occur. The dysfunctioning neural systems directly responsible for autism in non-retarded individuals must be sought elsewhere. Ten of the autistic subjects in this study, whom we found to have normal auditory brain-stem ERPs, had previously been found to have abnormalities in longer latency cognitive ERP components (Courchesne et al. 1984, 1985). We conclude, therefore, that those abnormalities in longer latency components are not the downstream consequences of abnormalities in the structures generating the auditory brain-stem ERPs recorded in the present study.

Adolescent↗

PubMed1988

Localization of callosal auditory pathways: a CT case study.

The position of the auditory pathways in the human corpus callosum has not been defined by modern imaging techniques. We report a case with a discrete hemorrhagic lesion in the posterior body of the corpus callosum. The only signs of disturbed callosal function were limited to the auditory system--suppression of left ear stimuli with dichotic listening and neglect of left-sided auditory simultaneous stimuli.

Adult↗

PubMed1990

Organization of the auditory pathway in the thoracic ganglia of noctuid moths.

We describe the neuroarchitecture of the noctuid thoracic nerve cord and use this framework to interpret the organization of the auditory pathway responsible for escape behaviour in noctuid moths. Noctuid moths possess only two auditory receptors (A1, A2), in each ear. The axon of the A1 cell projects initially to a glomerulus located ventrally and medially in the metathoracic ganglion, where it bifurcates. One branch ascends in the ventral intermediate tract to the brain, the other descends in the ventral intermediate tract into abdominal neuromeres of the metathoracic ganglion. Both axons arborize in the median ventral and ring tracts in each neuromere. The central projections of the A2 cell remain largely within the metathoracic ganglion. The axon bifurcates at the midline and directs arborizations dorsally to the dorsal intermediate and median dorsal tracts, and ventrally into the ring tract where the arborizations overlap those of the A1 afferent. The afferent projections remain ipsilateral to the ear of origin. We describe a posterior auditory association area in the metathoracic ganglion in which the major arborizations of several identified interneurones overlap those of the A1 afferent and make monosynaptic connections with it. These interneurones all respond tonically to sound stimuli. We have also identified the projections of the A1 afferent, interneurones, and motor neurones in the segmentally equivalent anterior auditory association area of the mesothoracic ganglion. An interneurone with major arborizations in the same tracts as the A1 afferent, and receiving monosynaptic input from it, is described. The arborizations of higher order interneurones lie mainly in dorsal tracts along with those of flight motor neurones. All the interneurones in this anterior centre respond phasically or phasic/tonically to sound stimuli. The relevance of this anatomical organization for predator avoidance behaviour is considered and the organization of auditory pathways in tympanate insects compared.

Animals↗

PubMed1994

Distribution of Fos-like immunoreactivity in the auditory pathway of the Sprague-Dawley rat elicited by cochlear electrical stimulation.

Fos-like immunoreactivity (FLI) was mapped in the auditory pathway of Sprague-Dawley rats in response to unilateral electrical stimulation of the cochlea implanted with two stimulating electrodes. Densely packed FLI neurons were widely distributed in the dorsal cochlear nucleus (more ipsilaterally than contralaterally), while FLI neurons were rare in the posteroventral cochlear nucleus and virtually absent in the anteroventral cochlear nucleus. Sparse FLI was detected in the superior olivary complex, the pontine nuclei and the ipsilateral dorsal nucleus of the lateral lemniscus, whereas the contralateral dorsal nucleus of the lateral lemniscus was moderately labeled. In the inferior colliculus, the pattern of FLI was similar on both sides, restricted mainly to its dorsal and external cortices. At the thalamic level, FLI neurons were seen in the dorsal and medial divisions of the medial geniculate body as well as in the peripeduncular nucleus. A significant increase of FLI was observed in the temporal cortex. This study demonstrates the presence of selective functional changes along the auditory pathway elicited by electrical stimulation of the cochlea, as revealed by FLI.

Acoustic Stimulation↗

PubMedDate not supplied

Activity elicited in the auditory pathway of the rat by electrical stimulation of the cochlea.

The activity elicited by electrical stimulation of the cochlea in the auditory pathway was assessed in an animal model of cochlear implants on the basis of the induction of the immediate early gene c-fos and single neuron recordings. Electrical stimulation of the cochlea induced Fos-like immunoreactivity in the cochlear nucleus, mainly in its dorsal nucleus, in the superior olivary complex, in the lateral lemniscus, but not in the central nucleus of the inferior colliculus, the main relay nucleus in the auditory midbrain. However, single unit recordings from the inferior colliculus, ipsilateral and contralateral to the electrically stimulated cochlea, showed clear responses of single neurons, reminiscent of those elicited by acoustic stimulation. These findings provide immunocytochemical and electrophysiological evidence that the various nuclei of the auditory pathway are activated by electrical stimulation of the cochlea.

Animals↗

PubMed1998

Antibody-dependent Fos-like immunoreactivity (FLI) in the auditory pathway of the rat in response to electric stimulation of the cochlea.

The distribution of Fos-like immunoreactivity (FLI) in the auditory pathway was analyzed and quantified in two groups of rats subjected to a similar electric stimulation of the cochlea, but the brains of the two groups were treated with a different antibody against Fos. The brains of control (unstimulated) rats were processed and analyzed in the same way. In a given auditory nucleus, for the same paradigm of stimulation, a very different density of FLI can be found depending on the antibody used to process the tissue. There are auditory nuclei which exhibited a significant activation of FLI as compared to control animals when one antibody was used whereas there was no difference when using the other antibody. In other cases, for both antibodies, a significant FLI increase was observed in relation to the stimulus. However, the increase of FLI density was significantly greater in some auditory nuclei with one antibody, while it was the reverse in other auditory nuclei. The present data demonstrate quantitatively that the use of two different Fos antibodies can strongly affect the FLI produced in the auditory pathway by electric stimulation of the cochlea, confirming previous qualitative observations based on acoustic stimulation of the cochlea.

Animals↗

PubMed1982

Organization of ascending auditory pathways in the pigeon (Columba livia) as determined by autoradiographic methods.

A mixture of tritiated proline and fucose was injected into the labyrinthine endolymphatic space of 5 white king pigeons (Columba livia). Using standard autoradiographic techniques, we observed transsynaptic labeling in ascending auditory pathways to the level of the mesencephalon. Auditory system structures, ipsilateral to the injection site, which labeled heavily were the cochlear nerve, the magnocellular and angular nuclei, and the superior olive. Those ipsilateral structures which were slightly labeled were the lateral lemniscus and the dorsal part of the lateral mesencephalic nucleus. Contralateral structures which labeled were the superior olive, lateral lemniscus, and dorsal part of the lateral mesencephalic nucleus. The results of this study suggest that ascending auditory pathways (to the level of the mesencephalon) in the pigeon are more similar to those described for mammals in general than previously thought.

Abducens Nerve↗

PubMedDate not supplied

Intracranial auditory pathways: anatomy correlated with evoked response data.

The intracranial auditory pathways are complex, and they have been incompletely mapped. The purpose of the communication is to summarize what is known about these fibers onto clinically relevant imaging sections. Anatomic information is correlated with the clinical auditory evoked responses currently used to localize lesions in these pathways. This linkage will improve communication between imagers and clinicians. In addition, it can be used for teaching.

Auditory Cortex↗

PubMed1983

Hereditary dysfunction of the brain stem auditory pathways as the major cause of speech retardation.

Grossly abnormal auditory brain stem responses (ABR) and abnormally high stapedius reflex thresholds were found in 2 pairs of siblings, not akin. Pure tone audiometry showed moderate to moderately severe hearing impairment in all 4 subjects, but neither the ABR findings nor the stapedius reflex thresholds were compatible with pure cochlear lesions. In all the cases the benefit from using hearing aids was conspicuously poor, and the development of oral language markedly retarded, one pair of siblings being essentially incapable of oral--aural communication. A cousin to one of the pairs of siblings showed similar but less pronounced symptoms and signs. Intelligence was judged to be normal in all 5 individuals and neurologic examination did not reveal CNS abnormalities besides the hearing impairment. We assume dysfunction of the brain stem auditory pathways to be the main cause of the speech retardation in the 2 pairs of siblings and the abnormality to be hereditary in nature.

Adolescent↗

PubMed1976

[Characteristics of the reactions of neurons of successive links in the auditory pathway to changes in the timing of acoustic signals].

Afferent impulsation was compared for different levels of the auditory system: the cochlear nuclei, posterior colliculi, and the auditory cortex. While moving from the cochlear nuclei over to the posterior colliculi and the auditory cortex, the number of neurons describing the temporal structure of the amplitude-modulated signal's envelope in the impulse activity pattern, becomes sharply reduced; the number of neurons selectively responding to certain phases of the envelope increases; the firing rate of neurons of the auditory pathway's higher levels decreases; the repetition rates becomes narrow due to limitation from both the high- and the low-frequency sides. Selectivity of responses to combination of such signal parameters as the frequency of the carrier and the rhythm of the amplitude modulation, increases. Specificity of the neuronal responses increases on certain combinations of such parameters of the frequency-modulated sounds as the frequency range in the signal, the direction and speed of the frequency modulation. The data obtained revealed some general tendencies of the impulsation transformation in successive levels of the auditory pathway.

Animals↗

PubMed1993

Network analysis of functional auditory pathways mapped with fluorodeoxyglucose: associative effects of a tone conditioned as a Pavlovian excitor or inhibitor.

The purpose of this study was to examine how opposite learned associative properties of the same auditory stimulus are represented by the pattern of network interactions between auditory system structures. [14C(U)]2-fluoro-2-deoxyglucose (FDG) autoradiography was used to compare mean auditory system activity and interregional correlations resulting from the presentation of a tone trained as either a Pavlovian conditioned excitor or inhibitor. Rats were trained with reinforced trials of the conditioned excitor (A+) intermixed with non-reinforced trials of a tone-light compound (AX-). For the Conditioned Excitor group, the tone was the excitor (A+), while for the Conditioned Inhibitor group the tone was the inhibitor (X-). After conditioning, both groups were injected with FDG and presented with the same tone. Structural equation models, constructed from the anatomical connections between auditory regions and their interregional correlations in FDG uptake, were used to calculate path coefficients representing the network interactions. The opposite associative significance of the tone was reflected as functional changes in the interactions between parallel auditory pathways. Direct covariance effects through lemniscal pathways from the ventral cochlear nucleus were similar in absolute magnitude but differed in sign between the Excitor and Inhibitor network models. Extra-auditory influences on the dorsal cochlear nucleus were greater for the tone-inhibitor, reflecting possible interactions of this nucleus with extra-auditory regions. The different associative effects of the tone suggest that central auditory pathways can code not only the physical qualities, but also the associative significance of auditory stimuli. These findings demonstrate that neural network interactions differentiate the associative effects of tones in the brain. It is proposed that associative learning is a distributed property of neural networks and that such a property can be understood by considering the interactions between component parts of the network.

Acoustic Stimulation↗