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At least 235 records · Page 13Linked to original sources
PubMed2004

Auditory sensitivity in children using the auditory steady-state response.

OBJECTIVE: To determine the effectiveness of auditory steady-state response (ASSR) as a measure of hearing sensitivity in young children suspect for significant hearing loss. DESIGN: Within-subject comparisons of click auditory brainstem response (ABR) thresholds and ASSR thresholds. SUBJECTS: The study population comprised 42 children suspect for hearing loss and subsequently referred for hearing assessment using electrophysiologic techniques. MAIN OUTCOME MEASURES: Electrophysiologic threshold responses for click ABR and ASSR stimuli (0.5, 1, 2, and 4 kHz) for right and left ears. RESULTS: Based on ABR and ASSR thresholds, 50% of the subjects demonstrated significant hearing loss in the severe to profound range. In some subjects, ASSRs were present at higher stimulus levels when click ABRs were absent. Significant correlations (P<.05) were found between high-frequency ASSR and click ABR thresholds for this study sample. For some subjects, ASSR findings suggested differences between ears that were not observable from the no-response click ABR results. CONCLUSIONS: Auditory steady-state response testing may provide additional information for children who demonstrate hearing levels in the severe to profound range. This information may be helpful when selecting the ear for cochlear implantation for a young hearing-impaired child. Multiple objective methods, such as ABR and ASSR testing, may be needed to determine accurate hearing sensitivity for young children being considered for sensory devices, and in particular, cochlear implants.

Audiometry, Pure-Tone↗
PubMed1990

Visual projections induced into the auditory pathway of ferrets. I. Novel inputs to primary auditory cortex (AI) from the LP/pulvinar complex and the topography of the MGN-AI projection.

The organization of cortical circuitry responsible for processing sensory information is a subject of intense examination. However, it is not known whether cortical cells in different sensory cortices process information in a way that is specific to the modality of their input, or whether there are commonalities in processing circuitry across different cortices. In our laboratory, this question has been investigated at the level of the geniculocortical pathway by routing information of one sensory modality into the processing circuitry of another modality. Appropriate early lesions cause growth of retinal axons into the auditory thalamus (MGN) (Sur et al., Science 242:1437, '88). Previously, we have established that the MGN carries the resulting visual information on to primary auditory cortex (AI), which thus contains visually responsive neurons and a topographic representation of the retina (Roe et al., Soc. Neurosci. Abstr. 14:460, '88; Sur et al., Science 242:1437, '88). In this paper, we describe anomalous projections from the dorsal part of the thalamus, specifically the lateral posterior/pulvinar complex, into AI. This result demonstrates that thalamic neurons belonging to one modality can be induced to project to cortex that is normally of a different modality. In addition, we have studied in detail the nature of the MGN to AI projection in these animals as compared to the normal projection. The MGN to AI projection appears to be unaltered by the lesions; the location and topography of labelled cells are similar to that in normal animals. Because the MGN to AI projection is still highly divergent along the "isofrequency" dimension when compared to the tonotopic dimension, our data suggest that visual topography in the cortical map is created within the auditory cortex, perhaps by activity-dependent sharpening of the retinal representation during development.

Animals↗
PubMed1978

A new auditory area of the songbird forebrain: a connection between auditory and song control centers.

Single unit microelectrode recordings followed by electrolytic lesions which mark the recording sites demonstrate that there is an auditory region of the songbird forebrain that is distinct from and superficial to field L, the primary auditory region of the telencephalon. The location of the superficial auditory area and its large cells suggest identification with HVc, the large-celled telencephalic nucleus which controls song in the canary.

Acoustic Stimulation↗
PubMed2001

Free-field unmasking response characteristics of frog auditory nerve fibers: comparison with the responses of midbrain auditory neurons.

Previous studies in the inferior colliculus have shown that spatial separation of signal and noise sources improves signal detection. In this study, we investigated the free-field unmasking response properties of single fibers in the auditory nerve--these were compared to those of inferior colliculus neurons under the same experimental conditions to test the hypothesis that central processing confers advantages for signal detection in the presence of spatially separated noise. For each neuron, we determined the detection threshold for a probe at the unit's best azimuth under three conditions: (1) by itself, (2) when a masker at a constant level was also presented at the unit's best azimuth, and (3) when the masker was positioned at different azimuths. We found that, on average, maskers presented at a unit's best azimuth elevated the probe detection threshold by 4.22 dB in the auditory nerve and 10.97 dB in the inferior colliculus. Angular separation of probe and masker sources systematically reduced the masking effect. The maximum masking release was on average 2.90 dB for auditory nerve fibers and 9.40 dB for inferior colliculus units. These results support the working hypothesis, suggesting that central processing contributes to the stronger free-field unmasking in the inferior colliculus.

Animals↗
PubMed1981

Threshold sensitivity of the auditory pathway: effects of worsening signal-to-noise ratio in the auditory nerve.

Perfusions of scala tympani with high potassium solutions increase spontaneous activity of auditory nerve fibres without affecting their threshold sensitivity. In these circumstances, however, the signal-to-noise ratio of the auditory nerve response to a given stimuli is worsened. Recordings from cochlear nucleus neurones during such perfusions indicate that this worsening is critical for threshold sensitivity at higher levels in the auditory pathway.

Acoustic Stimulation↗
PubMed1987

The maturation of the central auditory conduction in preterm infants until three months post term. I. Composite group averages of brainstem (ABR) and middle latency (MLR) auditory evoked responses.

Brainstem (ABR) and middle latency (MLR) auditory evoked responses were obtained sequentially in 49 preterm infants until three months post term date. In addition, the records of 16 preterm infants, obtained at different conceptional age levels, were included. The recording of these responses was performed successively in one procedure, together with auditory cortical evoked responses. The infants were divided into 5 groups according to their gestational age, i.e. the term at birth. Composite group averages were determined, showing the group stable components of the 5 gestational age groups at 8 different conceptional age levels, i.e. term at the time of the recording. The intra group stable components could thus be determined for further study of developmental trends in the responses. The group averages also serve as a reference in the visual analysis of the individual records. The averaged ABRs showed that with increasing conceptional age increasingly better identifiable waveforms were obtained. These were particularly outstanding for peaks I and V ipsilateral to stimulation, and peaks IIc and Vc contralateral to stimulation. This enabled the measurement of the central conduction times. The MLRs were especially remarkable for their latency changes which occurred in peak PO and the troughs Na and Nb. The results indicated that the conduction of the subcortical auditory afferent signals can be measured successfully in groups of very premature infants with ABRs and MLRs.

Audiometry, Evoked Response↗
PubMed1996

Response properties of units in the posterior auditory field deprived of input from the ipsilateral primary auditory cortex.

The influence of the ipsilateral primary auditory field (AI) on the response properties of neurons in the posterior auditory field (Field P) was examined in three cats anesthetized with sodium pentobarbital. Rate/level functions were obtained, by extracellular recording, from single units in Field P before (n = 38) and after (n = 50) subpial aspiration of AI. The ablations were primarily confined to the medial ectosylvian gyrus, although in one case extended into the high-frequency portion of the anterior auditory field. Comparisons between the behavior of units isolated before and after AI ablation failed to demonstrate any changes in the response properties of neurons in Field P attributable to the ablation. Nonmonotonic response profiles, first spike latency, variability in latency, threshold and maximal discharge rates of the units to acoustic stimuli were not significantly altered by the AI ablation. These results indicate that the basic response properties of neurons in Field P do not depend on input from the ipsilateral AI. This suggests that these properties are most likely determined by thalamic input or by circuitry within Field P.

Acoustic Stimulation↗
PubMed2004

Auditory middle-latency components to fusion of speech elements forming an auditory object.

OBJECTIVE: The purpose of this study was to define early brain activity associated with fusion of speech elements to form an auditory object in the middle-latency range preceding the F-Complex. METHODS: Stimuli were binaural formant transition and base, that were presented separately or fused to form the vowel-consonant-vowel sequence /ada/. Eleven right-handed, adult, native Hebrew speakers listened to 2/s presentations, and the brain potentials from C(z) during the 250 msec following transition onset (in the responses to transition and to the fused word) or following the time it would have been presented (in the response to base alone) were recorded. The net-fusion response was extracted by subtracting the sum of potentials to the base and the formant transition from the potentials to the fused sound. RESULTS: Auditory middle-latency components, comprising of 9 peaks and troughs were recorded in response to the base, to the formant transition and to the fused /ada/. In general, the responses to the fused object were significantly smaller in peak amplitude and in total activity (area under the curve) resulting in the difference waveform of the net-fusion response that also included 9 peaks, but with opposite polarities. CONCLUSIONS: The early middle-latency components to fusion indicate that the fusion of speech elements to a word involves inhibition, occlusion or both. The results are in line with the uniqueness of speech perception and the early role of the auditory cortex in speech analysis.

Acoustic Stimulation↗
PubMed2005

Auditory processing--speech, space and auditory objects.

There have been recent developments in our understanding of the auditory neuroscience of non-human primates that, to a certain extent, can be integrated with findings from human functional neuroimaging studies. This framework can be used to consider the cortical basis of complex sound processing in humans, including implications for speech perception, spatial auditory processing and auditory scene segregation.

Acoustic Stimulation↗
PubMed2005

Localization of human supratemporal auditory areas from intracerebral auditory evoked potentials using distributed source models.

While source localization methods are increasingly developed to identify brain areas underlying scalp electro/magnetoencephalographic data (EEG/MEG), these methods have not yet been used to identify the sources of intracerebral signals which offer highly detailed information. Here, we adapted the minimum current estimates method to intracranial data in order to localize supratemporal sources of intracerebral auditory 1-kHz-tone-evoked potentials occurring within 100 ms after stimulus onset. After an evaluation of localization method and despite inter-subject variability, we found a common spatiotemporal pattern of activities, which involved the first Heschl's gyrus (H1) and sulcus (HS), the Planum Temporale (PT), H2/H3 when present, and the superior temporal gyrus (STG). Four time periods of activity were distinguished, corresponding to the time range of the scalp components P0, Na, Pa/Pb, and N100. The sources of the earliest components P0 (16-19 ms) and Na (20-25 ms) could be identified in the postero-medial portion of HS or H1. Then, several areas became simultaneously active after 25 ms. The Pa/Pb time range (30-50 ms) was characterized by a medio-lateral and postero-anterior propagation of activity over the supratemporal plane involving successively H1/HS, the Planum Temporale, H2/H3 when present, and the STG. Finally, we found to a large extent that the N100 (55-100 ms) involved almost the same areas as those active during the Pa/Pb complex, with a similar propagation of activities. Reconstructing scalp data from these sources on fictive EEG/MEG channels reproduced classical auditory evoked waveforms and topographies. In conclusion, the spatiotemporal pattern of activation of supratemporal auditory areas could be identified on the individual anatomy using current estimates from intracerebral data. Such detailed localization approach could also be used prior to epilepsy surgery to help identify epileptogenic foci and preserve functional cortical areas.

Acoustic Stimulation↗
PubMed2001

Auditory evoked potentials from auditory cortex, medial geniculate nucleus, and inferior colliculus during sleep-wake states and spike-wave discharges in the WAG/Rij rat.

OBJECTIVE: Click auditory evoked potentials (AEP) were simultaneously recorded from the auditory cortex (ACx), the medial geniculate nucleus (MGN), and the inferior colliculus (IC) in the freely moving WAG/Rij rat, to investigate state-dependent changes of the AEP in different anatomical locations along the auditory pathway. METHODS: AEPs obtained during active (AW) and passive wakefulness (PW), slow wave sleep (SWS), rapid-eye-movement sleep (REM) and generalized spike-wave discharges (SWD; a specific trait of the WAG/Rij rat, a genetic model for absence epilepsy), were compared. RESULTS: The early components in ACx, MGN and IC were stable throughout the sleep-wake cycle and SWD, apart from a slight increase in the IC during SWD. At all three locations a prominent enlargement of a later component (i.e., N32 in IC, N33 in MGN, and N44 in ACx) was found during SWS and SWD. CONCLUSIONS: The early AEP components are not modulated by the normal sleep-wake states, and are not impaired during SWD. A strong state-dependent modulation of a later AEP component occurs at all three anatomical locations investigated. This suggests that apart from the thalamic burst firing mode, additional mechanisms must exist for the enlargement of the AEP during EEG-synchronized states at the prethalamic and cortical level.

Action Potentials↗
PubMed2000

Expression of NMDA, AMPA and GABA(A) receptor subunit mRNAs in the rat auditory brainstem. I. Influence of early auditory deprivation.

Impact of early post-natal deafening on auditory pathways was investigated in newborn rats deafened by daily amikacin injections from P7 to P16 inducing a complete destruction of the organ of Corti. The expression of mRNAs encoding N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) and gamma-aminobutyric acid type A (GABA(A)) receptor subunits was then studied by in situ hybridization in the dorsal and ventral cochlear nucleus and in the central nucleus of the inferior colliculus (CNIC). Early post-natal deafening decreased bilaterally the expression of mRNAs encoding NR1, NR2a, NR2b and flop isoforms of AMPA receptors. On the contrary, it increased the expression of mRNAs encoding some GABA(A) subunits (alpha1, beta1, gamma2) and flip isoforms of AMPA receptors. These changes were more pronounced in cochlear nuclei than in CNIC. They suggest that auditory sensation is essential in the normal development of central auditory pathways.

Amikacin↗
PubMed1997

Auditory threshold sensitivity of the human neonate as measured by the auditory brainstem response.

The absolute auditory sensitivity of the human newborn infant was investigated using auditory brainstem response thresholds (ABR). ABRs were elicited with clicks and tone-bursts of 0.5, 1.5, 4.0 and 8.0 kHz, embedded in notched noise, in healthy, full-term human neonates and young adults with known, normal-hearing sensitivity. Stimuli were calibrated using a probe microphone positioned near the tympanic membrane in the ear canal of each subject to control for differences in resonance characteristics of infant and adult ear canals. ABR thresholds were also characterized relative to group psychophysical thresholds (nHL) and relative to individual psychophysical threshold or sensation level (SL) for the adult subjects. Infant ABR thresholds measured in p.e. SPL for all stimuli are elevated by to 3-25 dB relative to adult thresholds. Threshold elevation is greatest for the high-frequency stimuli. Result are consistent with neural immaturity for high-frequency stimuli in the auditory system of human neonates.

Acoustic Stimulation↗
PubMed2002

Effect of deviant probability and interstimulus/interdeviant interval on the auditory N1 and mismatch negativity in the cat auditory cortex.

In passive oddball paradigm the effects of changes in interstimulus/interdeviant interval (ISI; IDI) and deviant probability were investigated on mismatch negativity (MMN), auditory N1 wave and the exogenous P1 component of the auditory event-related potential in the cat. An epidural electrode matrix was chronically implanted over the auditory fields of the neocortex, and the amplitudes of the aforementioned components were measured in the location of their amplitude maxima. Dependence of the MMN both on the ISI and IDI as well as deviant probability was revealed, while the amplitude of the P1 and N1 showed dependence merely on the ISI. This method can be used for separation of the two negative, often overlapping components in the cat.

Acoustic Stimulation↗
PubMed2002

Maturation of human central auditory system activity: separating auditory evoked potentials by dipole source modeling.

OBJECTIVES: Previous studies have shown that observed patterns of auditory evoked potential (AEP) maturation depend on the scalp location of the recording electrodes. Dipole source modeling incorporates the AEP information recorded at all electrode locations. This should provide a more robust description of auditory system maturation based on age-related changes in AEPs. Thus, the purpose of this study was to evaluate central auditory system maturation based dipole modeling of multi-electrode long-latency AEPs recordings. METHODS: AEPs were recorded at 30 scalp-electrode locations from 118 subjects between 5 and 20 years of age. Regional dipole source analysis, using symmetrically located sources, was used to generate a spatio-temporal source model of age-related changes in AEP latency and magnitude. RESULTS: The regional dipole source model separated the AEPs into distinct groups depending on the orientation of the component dipoles. The sagittally oriented dipole sources contained two AEP peaks, comparable in latency to Pa and Pb of the middle latency response (MLR). Although some magnitude changes were noted, latencies of Pa and Pb showed no evidence of age-related change. The tangentially oriented sources contained activity comparable to P1, N1b, and P2. There were various age-related changes in the latency and magnitude of the AEPs represented in the tangential sources. The radially oriented sources contained activity comparable to the T-complex, including Ta, and Tb, that showed only small latency changes with age. In addition, a long-latency component labeled TP200 was observed. CONCLUSIONS: It is possible to distinguish 3 maturation groups: one group reaching maturity at age 6 and comprising the MLR components Pa and Pb, P2, and the T-complex. A second group that was relatively fast to mature (50%/year) was represented by N2. A third group was characterized by a slower pattern of maturation with a rate of 11-17%/year and included the AEP peaks P1, N1b, and TP200. The observed latency differences combined with the differences in maturation rate indicate that P2 is not identical to TP200. The results also demonstrated the independence of the T-complex components, represented in the radial dipoles, from the P1, N1b, and P2 components, contained in the tangentially oriented dipole sources.

Acoustic Stimulation↗
PubMed2004

Auditory neuropathy in hyperbilirubinemia: is there a correlation between serum bilirubin, neuron-specific enolase levels and auditory neuropathy?

This study evaluated whether a correlation exists between increased serum bilirubin and neuron-specific enolase (NSE) assays (a biochemical index of neuronal damage) and auditory neuropathy. Nineteen term neonates without hemolysis whose serum bilirubin levels were above 20 mg/dl and 27 healthy term newborns with bilirubin levels <13 mg/dl were included in the study. Auditory brainstem responses (ABRs) and transient evoked otoacoustic emissions (TEOAEs) of patients with hyperbilirubinemia were obtained before discharge. This preliminary study did not show any correlation between the serum NSE and bilirubin values. However, infants who had auditory neuropathy had significantly higher NSE levels, and thus these patients, being in the high-risk group, need close follow-up.

Auditory Diseases, Central↗
PubMed2004

Human auditory cortical dynamics during perception of long acoustic sequences: phase tracking of carrier frequency by the auditory steady-state response.

We recorded human auditory cortical activity during the perception of long, changing acoustic signals and analyzed information provided by dynamic neural population measures over a large range of time intervals (approximately 24 ms-5 s). Participants listened to musical scales that were amplitude modulated at a rate of 41.5 Hz, generating an ongoing, stimulus-related oscillatory brain signal, the auditory steady-state response (aSSR). The aSSR generated energy at the amplitude modulation rate that was recorded using magnetoencephalography. As in previous work, the timing (phase) of this response varied with stimulus carrier frequency over the entire course of minute-long tone sequences ('phase tracking' of carrier frequency). The length of the time interval over which phase was calculated was systematically varied; significant phase tracking was regularly observed at analysis intervals of <50 ms in length. The right auditory cortex exhibited better phase tracking performance than the left at analysis intervals of 24-240 ms, and frequency dependent phase delays were consistently larger than those predicted by cochlear mechanics. Based on these empirical data, a model of the neural populations responsible for phase tracking suggests that it is produced by a subpopulation ( approximately 25%) of the cells generating the aSSR.

Acoustic Stimulation↗
PubMed2002

Auditory sensory impairment in children with oral clefts as indexed by auditory event-related potentials.

Children with nonsyndromic oral clefts and with the CATCH 22 syndrome (acronym for cardiac defects, abnormal faces, thymus hypoplasia, clefts, and hypocalcemia) display a range of language and learning disabilities, the neurofunctional bases of which are not yet understood. This review summarizes recent event-related brain potential (ERP) studies on central auditory processing in infants and children with different cleft types and presents an effort to integrate these ERP and earlier behavioral findings into a workable hypothesis on the mechanisms of cognitive impairment in the oral cleft population. The encoding of the acoustic sound features and the functioning of auditory sensory memory (ASM) were studied by recording cortical auditory ERPs. Tapped were two ASM functions: tone pitch discrimination and the duration of sensory memory for tone pitch. In infants with cleft palate, tone pitch discrimination was impaired at birth and at 6 months of age. In infants with cleft lip and palate, no ASM impairment was detected at either age. In school-aged children with clefts and CATCH 22 syndrome, the discrimination of tone pitch was intact under optimal stimulation conditions. However, in these children, shortened duration of ASM was observed, with the magnitude of its shortening covarying with cleft type and being most pronounced in children with CATCH 22 syndrome. The different types of ASM dysfunction found in children with different cleft types could not be accounted for by the peripheral hearing deficits. The relation between ASM dysfunction and known behavioral cognitive disability profiles in children with different cleft types suggests that ASM is implicated in language disabilities of children with oral clefts. Furthermore, it appears that the ASM impairment and oral clefting are linked in a comorbid fashion.

Analysis of Variance↗