Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Auditory Pathways”

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 667 records · Page 37Linked to original sources
PubMedDate not supplied

Estimates of essential neural elements for stimulation through a cochlear prosthesis.

Electrical stimulation of afferent auditory pathways through electrodes placed within and outside of the cochlea were used to study stimulation and design parameters relevant to a cochlear prosthesis. In the acute guinea pig preparation, the tract response evoked in brachium of the inferior colliculus by electrical stimulation to an ear provided estimates of the effectiveness of various electrode placements. Stimulation between an electrode in the cochlea and a site along the eighth nerve was characterized by the lowest thresholds. Stimulation between intracochlear electrodes was somewhat less effective, and stimulation between external electrodes at the nerve, cochlear nucleus, or distant point was least effective. Thresholds, expressed as current, rose at approximately 6 dB per octave for stimulus frequencies from 1 kHz to 16 kHz. Thresholds below 10 microA rms were seen for optimal placements. These observations suggest that the neural elements being stimulated are the cell bodies of the spiral ganglion cells.

Afferent Pathways↗
PubMed2005

[The features of auditory brainstem response in patients with obstructive sleep apnea-hypopnea syndrome].

OBJECTIVE: To investigate the effects and causes of obstructive sleep apnea-hypopnea syndrome (OSAHS) on auditory pathway, the changes of auditory brainstem response (ABR) were analyzed. METHOD: With the use of polysomnography,72 snorers were examined and divided into OSAHS and non- OSAHS groups. These two groups patients and a group of normal person were underwent ABR measuring. RESULT: There were statistically significant difference between the group of OSAHS and the non-OSAHS or the group of OSAHS and the normals on the delayed latency of wave I and wave V, the response liminal value of wave V rised. CONCLUSION: The results suggest that cochlear function may be affected in patient with OSAHS, the effected of brain stem is unknown.

Adult↗
PubMedDate not supplied

[Middle and late latency auditory evoked potentials in adults with AIDS].

BACKGROUND: Middle and late latency auditory evoked potentials. AIM: to verify the occurrence of middle and late latency auditory evoked potentials disorders in adults with Acquired Immunodeficiency Syndrome (AIDS). METHOD: Middle and late latency auditory evoked potentials of 8 individuals with AIDS, with ages ranging from 10 to 51 years, with normal hearing, or with sensoryneural hearing losses up to moderate, and normal results in the Auditory Brainstem Response, comparing the results with the responses obtained for a control group which was composed by 25 individuals, with ages ranging from 19 to 24 years, with no hearing complaints and with normal hearing and normal results in the Auditory Brainstem Response. RESULTS: The Pa wave latency and amplitude averages in the C3/A2 and C4/A1 modalities, and the average of the P300 wave were analyzed. No significant differences were observed in the Pa wave amplitude and latency averages between the groups, although a non-statistically significant increase was observed in the latency and a decrease in the amplitude of such wave for the research group in the C3/A2 modality. The latency of the P300 wave was significantly longer to the left for the research group. It was also observed a longer latency to the right, although this was not statistically significant. CONCLUSION: Adult individuals with AIDS do not present alterations in the middle latency auditory evoked potential and do present alterations in the cognitive potential, indicating a disorder in the cortical regions of the auditory pathway and a deficit in the cognitive processing of auditory information for this population. Such findings stress the importance of a careful investigation of the auditory function of individuals with AIDS, thus favoring the therapeutic planning.

Acoustic Stimulation↗
PubMedDate not supplied

[Evoked auditory potentials in neonatal hyperbilirubinemia].

Neonatal hyperbilirubinemia (greater than 20 mg%) is an audiological risk factor. In order to check early detection of bilirubin-induced neurological damage in the brainstem, 19 newborns were enrolled in the present study. The criteria was a bilirubin level ranging from 12 to 20 mg%. A likely mechanism for bilirubin intoxication may be the slowing and desynchronization of acoustic stimuli in the brainstem. Auditory brainstem responses were performed using non filtered clicks at 100 dB SPL (peak equivalent). Absolute and interpeak latencies of waves I and V were measured and correlated to bilirubinemia upon acoustic stimulation and maximal bilirubinemia observed during neonatal observation. Significant correlations were noted between bilirubinemia and V or V-I latencies. No significant correlation was observed between bilirubinemia and wave I latencies. Similar results were obtained in a restricted group of term neonates with hyperbilirubinemia. It is, thus, concluded that hyperbilirubinemia affects the upper auditory pathways.

Auditory Pathways↗
PubMed1997

Development of adult-type inhibitory glycine receptors in the central auditory system of rats.

Inhibitory synaptic activity is crucial for many aspects of acoustic information processing and mainly mediated by glycine and gamma-aminobutyric acid, the two principal inhibitory neurotransmitters in the auditory system. Glycine exerts its inhibitory action via binding to postsynaptic receptors existing in various isoforms. Here we have investigated the spatiotemporal distribution of adult-type, strychnine-sensitive glycine receptors (GlyRs) in the rat auditory system by using a specific antibody against the ligand-binding alpha1 GlyR subunit. In adults, alpha1 GlyRs were found at all relay stations of the auditory pathway except for the medial geniculate body and the auditory cortex. In most brainstem nuclei, labeling was characterized by dense clusters of heavily immunoreactive puncta outlining the somata and proximal dendrites, indicative of a powerful glycinergic inhibition. No alpha1 immunoreactivity was seen in the auditory system of fetal rats, consistent with results obtained by others in the spinal cord. At birth, labeling was weak and restricted to defined nuclei of the cochlear nuclear complex and the superior olivary complex. By postnatal day 8, labeling was seen in all brainstem nuclei. At the first appearance of immunoreactivity, alpha1 GlyRs were diffusely distributed on the neuronal surface, yet they became clustered with age, finally densely incrusting the somata and proximal dendrites between the 3rd and 4th postnatal week, when the mature pattern of immunoreactivity was established. We never observed an overexpression of alpha1 GlyRs or a transient appearance in areas that are devoid of the receptor in adults. The late formation of glycinergic synapses harboring the adult-type GlyRs in the auditory system, at a time when internuclear connections have already formed, indicates that alpha1 GlyRs do not participate in early synaptogenesis.

Aging↗
PubMed2001

Asymmetrical localization of benzodiazepine receptors in the human auditory cortex.

In humans, administration of benzodiazepines (BZD) has been shown to have an asymmetrical effect on the medial olivocochlear system. Indeed, a decrease of evoked otoacoustic emission suppression by contralateral acoustic stimulation, which explores the medial olivocochlear efferent system, was observed in the right ear, with no left ear effect. This result suggests a possible left-right auditory pathway BZD receptor asymmetry. Given the anatomical link between auditory centers and the medial olivocochlear system, the existence of a larger volume of cortical connecting fibers in the left hemisphere, and the possible link between BZD receptor density and neuronal density, we tested the hypothesis of an asymmetrical localization of BZD receptors in the auditory system in 10 right-handed subjects using [11C]flumazenil positron emission tomography. Semi-quantitative measurements of flumazenil binding were evaluated in Heschl's gyrus showing a left-right asymmetry in favor of left auditory cortex. This result indicates a higher density of neurons in left auditory cortex. The possible link between neurochemical asymmetry and functional asymmetry, and the perceptual outcome of BZD administration, will be discussed.

Adult↗
PubMedDate not supplied

Auditory evoked potential responses in chronic malnourished children.

Auditory evoked potential responses were recorded in 20 chronic malnourished children in age group 3-6 years and in 20 healthy age and sex matched controls using an 5200 Neuropack plus ( Nihon Koden, Japan) evoked potential recorder. The absolute peak latencies, inter peak latencies and amplitude of waves I-V of brainstem auditory evoked potentials (BAEPs) were analyzed. The mid latency responses (MLRs) were also studied in these children. Malnutrition was characterized by stunting, which indicated chronicity of nutritional deprivation. The children with chronic Protein energy malnutrition (PEM) had prolonged peak latencies of waves I, II, III and IV. The interpeak latencies I-III and III-V were also prolonged. The amplitude of wave I and V did not show any significant difference as compared to controls. The middle latency responses were not significantly different from the controls. Thus malnutrition affects the peripheral developmental process of auditory pathways only in the brainstem and the central thalamocortical projections of these pathways are spared.

Auditory Pathways↗
PubMed1995

Effects of carbamazepine and valproate on brainstem auditory evoked potentials in epileptic children.

Brainstem auditory evoked potentials (BAEPs) were recorded in 18 epileptic children receiving carbamazepine and 10 epileptic children receiving valproate. BAEPs were recorded before the administration of antiepileptic drugs (AEDs) and 13 months later during which the children received AEDs. Statistical analysis of peak latencies and interpeak intervals of waves I-III-V were made. Carbamazepine treatment resulted in prolongation of peak latencies of waves I-III-V and interpeak intervals I-III and I-V. Valproate monotherapy, on the other hand, caused no consistent changes on BAEP. On the basis of these results we suggest that chronic carbamazepine therapy exerts a suppressive influence on the auditory pathways, both peripherally at the level of the cochlea and/or auditory nerve, and centrally at the brainstem.

Anticonvulsants↗
PubMed1996

Middle latency auditory evoked potentials (MLAEPs) in (MS).

Middle latency auditory evoked potentials (MLAEPs) were studied in 30 definite multiple sclerosis (MS) patients in addition to brain-stem auditory evoked potentials (BAEPs). BAEP abnormalities were detected in 18 (60%) patients. MLAEPs were abnormal in 22 (73%) of them. In 15 patients BAEPs and MLAEPs were both abnormal. MLAEPs were found abnormal in 7 of the 12 patients with normal BAEPs. In 18 patients with abnormal BAEPs only 3 had normal MLAEPs. MLAEPs abnormalities are consistent with a rostral auditory pathway involvement. Therefore, they can be used in combination with BAEPs to examine the whole auditory system to improve the sensitivity.

Adolescent↗
PubMedDate not supplied

N1 action potentials in humans. Influence of simultaneous contralateral stimulation.

N1 action potentials, elicited by low-level, 4.0-kHz filtered clicks, were recorded from the ear canals of normal-hearing adults. Responses were recorded at two sensation levels in the presence and absence of a pure tone delivered to the contralateral ear. Waveforms were analysed for changes in amplitude and latency. A significant reduction in the amplitude of N1 was observed following the introduction of the contralateral tone at both FC levels. A concomitant change in latency was not observed. For all subjects, ipsilateral and contralateral signals were below the intensities which resulted in acoustic reflexes and crossover of contralateral signals. These data suggest that the N1 amplitude reduction observed in this study represents inhibitory activity of the efferent auditory pathway.

Acoustic Stimulation↗
PubMed1997

Developmental changes in P1 and N1 central auditory responses elicited by consonant-vowel syllables.

Normal maturation and functioning of the central auditory system affects the development of speech perception and oral language capabilities. This study examined maturation of central auditory pathways as reflected by age-related changes in the P1/N1 components of the auditory evoked potential (AEP). A synthesized consonant-vowel syllable (ba) was used to elicit cortical AEPs in 86 normal children ranging in age from 6 to 15 years and ten normal adults. Distinct age-related changes were observed in the morphology of the AEP waveform. The adult response consists of a prominent negativity (N1) at about 100 ms, preceded by a smaller P1 component at about 50 ms. In contrast, the child response is characterized by a large P1 response at about 100 ms. This wave decreases significantly in latency and amplitude up to about 20 years of age. In children, P1 is followed by a broad negativity at about 200 ms which we term N1b. Many subjects (especially older children) also show an earlier negativity (N1a). Both N1a and N1b latencies decrease significantly with age. Amplitudes of N1a and N1b do not show significant age-related changes. All children have the N1b; however, the frequency of occurrence of N1a increases with age. Data indicate that the child P1 develops systematically into the adult response; however, the relationship of N1a and N1b to the adult N1 is unclear. These results indicate that maturational changes in the central auditory system are complex and extend well into the second decade of life.

Acoustic Stimulation↗
PubMed1988

Neonatal deafening alters nonpyramidal dendrite orientation in auditory cortex: a computer microscope study in the rabbit.

In order to examine the influence of afferent input on nonpyramidal dendrite development in the auditory cortex, unilateral deafening was carried out in neonatal rabbits at birth, approximately 6 days prior to the onset of hearing. Deafening was produced by surgical removal of the incus and stapes ossicles, aspiration of the cochlear perilymph, and kanamycin injection into the oval window. At 60 days of age, acoustic stimulation of the deafened ear was unable to evoke auditory brainstem responses. The brains of experimental and littermate control rabbits were processed according to the Golgi-Cox Nissl method. The dendritic systems of lamina III/IV spine-free nonpyramidal cells in the auditory cortex contralateral to the deafened ear were digitized from 340-micron-thick coronal sections with the aid of a computer microscope. Three-dimensional spatial and statistical analyses revealed that nonpyramidal dendrite length in neonatally deafened rabbits increased 27% relative to littermate controls. A fan-in projection analysis revealed that the increased dendrite length in the deafened animals was maximum in the tangential direction and toward the white matter. Computer rotation of digitized neurons from neonatally deafened rabbits also revealed evidence of abnormal dendritic growth in the form of recurved dendrites. We interpret our results to indicate that unilateral cochlear destruction early in development causes a reorganization of the ascending auditory pathway which extends to the contralateral cerebral cortex. Because the auditory cortex contralateral to the deafened ear still receives acoustic input from the undamaged ipsilateral ear, normal nonpyramidal dendritic growth in the auditory cortex is, in part, dependent upon afferent activity arising from both ears.

Animals↗
PubMed2006

Phosphorylated cAMP response element-binding protein levels in guinea pig brainstem auditory nuclei after unilateral cochlear ablation.

After left unilateral cochlear ablation (UCA) in young adult guinea pigs, the appearance of plasticities in auditory pathways suggested altered gene expression and modified phenotypic behaviors of auditory neurons. Because phosphorylated cyclic-AMP response element-binding protein (CREB-P) is a transcription factor that binds to certain genes to facilitate their expression, CREB-P levels were measured after UCA and correlated with postablation plasticities. After UCA, Western blotting was employed to quantify CREB-P levels and illustrate CREB levels in the anteroventral (AVCN), posteroventral (PVCN), and dorsal (DCN) cochlear nucleus; the lateral (LSO) and medial superior olive (MSO); the medial nucleus of the trapezoid body (MNTB); and the central nucleus of the inferior colliculus (ICc) for up to 145 days. We also quantified the levels of several protein synthesis regulators and synaptic markers in the AVCN at 60 days. Sucrose-based extraction buffer improved CREB-P recovery. CREB-P levels became depressed at 3 and 7 postablation days, except in the PVCN, where they were elevated at 7 days, and in the ICc, where they were elevated at both times. At 60 days, CREB-P levels in all the nuclei were elevated. In the AVCN, levels of the protein synthesis regulators and synaptic markers were also elevated at 60 days. By 145 days, CREB-P levels again declined, except in the AVCN, where elevations persisted and increased on the ablated side, and in the ICc, where CREB-P elevations remained. The changes in CREB-P levels coincided with several plasticities in glutamatergic and glycinergic transmitter release and receptor activities, and alterations in neurotrophic support, that developed after UCA. These findings suggest that UCA altered CREB-P levels, which in turn might have contributed to plasticities that appear after UCA.

Animals↗
PubMed1990

Investigation of central auditory nuclei in the budgerigar with cytochrome oxidase histochemistry.

Cytochrome oxidase (CO) histochemistry was used to study the organization of central auditory structures in the budgerigar (Melopsittacus undulatus). In contrast to prior studies in birds showing that acetylcholinesterase staining is most intense within hindbrain auditory structures CO staining was prominent at all levels of the auditory pathway including the thalamus (i.e. nucleus ovoidalis) and primary telencephalic auditory area (Field 'L'). Furthermore, CO staining clearly distinguishes the boundaries of Field 'L' from adjacent portions of the neostriatum intermedium pars dorsolateralis which do not receive input from the auditory thalamus. Thus CO staining can be used as a marker for distinguishing auditory and non-auditory portions of the avian telencephalon.

Animals↗
PubMed2004

Age-dependent changes in the lateral superior olive of the gerbil (Meriones unguiculatus).

Data from humans and animal models provide evidence for an age-dependent impairment in the ability to localize sound. The lateral superior olive (LSO) in the ascending auditory pathway is one important center involved in processing of binaural auditory stimuli. To identify potential age-dependent changes we characterized the LSO in young (< 15 months) and old (> or =3 years) gerbils with a special emphasis on the expression of GABA- and glycine-like immuno-reactivity. The dimensions of the LSO, as well as the number and density of glycine- and GABA-immuno-reactive neurons, were not significantly different between young and old gerbils. The size of glycine- and GABA-immuno-reactive neurons was significantly reduced in the high-frequency (medial) limb of the LSO. Over all, age-dependent changes in the LSO of the gerbil were small.

Aging↗
PubMed1994

Audio-motor interface in anurans.

Like males of many anuran species, fire-bellied toads (Bombina orientalis) call antiphonally, which demonstrates an auditory input into the call-generating network. Males produce their calls by an inspiratory airstream, which is generated exclusively by contraction of the muscles of the buccal cavity. The painted frog (Discoglossus pictus) possesses a combined inspiratory and expiratory call mechanism, and also uses only buccal muscles. These muscles are controlled by branchial motoneurons, which receive vocal premotor input mainly from the pretrigeminal nucleus. The interconnections between the auditory pathway and the vocal pathway were examined by neuroanatomical tracing and intracellular recording. Mesencephalic auditory nuclei, laminar and magnocellular nucleus of the torus semicircularis, and tegmental nuclei constitute strong descending efferents, which, in turn, form collaterals that terminate in vocal premotor nuclei. These findings imply fast audio-vocal interfacing, which is a prerequisite for the control of antiphonal calling.

Animals↗