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 1,369 records · Page 76Linked to original sources
PubMed2004

Effects of location, frequency region, and time course of selective attention on auditory scene analysis.

Often, the sound arriving at the ears is a mixture from many different sources, but only 1 is of interest. To assist with selection, the auditory system structures the incoming input into streams, each of which ideally corresponds to a single source. Some authors have argued that this process of streaming is automatic and invariant, but recent evidence suggests it is affected by attention. In Experiments 1 and 2, it is shown that the effect of attention is not a general suppression of streaming on an unattended side of the ascending auditory pathway or in unattended frequency regions. Experiments 3 and 4 investigate the effect on streaming of physical gaps in the sequence and of brief switches in attention away from a sequence. The results demonstrate that after even short gaps or brief switches in attention, streaming is reset. The implications are discussed, and a hierarchical decomposition model is proposed.

Attention↗
PubMed2006

Early otitis media with effusion, hearing loss, and auditory processes at school age.

OBJECTIVES: To examine the effect of conductive hearing loss (HL) secondary to otitis media with effusion (OME) in the first 3 years of life on physiologic, peripheral, and higher-order behavioral auditory measures examined at school age. METHODS: Peripheral hearing sensitivity for conventional and extended high-frequency audiometric ranges, physiologic (distortion product otoacoustic emissions, contralateral and ipsilateral acoustic middle ear muscle reflexes), auditory brain stem response (ABR), and higher-order auditory processing measures (masking level difference; Virtual Auditory Localization, Speech Intelligibility Gain; adaptive Pediatric Speech Intelligibility task) were examined at the end of the second grade of elementary school in two cohorts (North Carolina, N = 73, and New York, N = 59). All participants (mean age, 8 years) were followed prospectively in infancy and early childhood (7 to 39 months) for middle ear status and hearing loss (using pneumatic otoscopy/tympanometry and repeated conditioned behavioral audiometric response procedures). Multivariate analyses were conducted to address whether early OME and early conductive HL were related to physiologic, peripheral, and higher-order auditory processes. RESULTS: Early hearing loss and OME were significantly associated with peripheral hearing at school age; extended high-frequency thresholds accounted for the result. Similarly, hearing loss in early life and OME were significantly associated with the acoustic middle ear muscle reflex: The contralateral stimulation condition accounted for the association. Significant associations with both early OME and early HL were also found for the auditory brain stem response measure and were explained by the correlations between early hearing loss and the ABR Wave V latency but not other ABR indices. There were no reliable associations between either early OME or early HL on any other auditory processes evaluated at the end of second grade. CONCLUSIONS: Extended high-frequency hearing and brain stem auditory pathway measures in childhood were significantly associated with children's experiences with OME and hearing loss from 7 to 39 months of age. However, no significant associations were found for psychoacoustic measures of binaural processing or a behavioral adaptive speech-in-noise test at school age.

Auditory Cortex↗
PubMed2004

Fast inhibition alters first spike timing in auditory brainstem neurons.

Within the first processing site of the central auditory pathway, inhibitory neurons (D stellate cells) broadly tuned to tonal frequency project on narrowly tuned, excitatory output neurons (T stellate cells). The latter is thought to provide a topographic representation of sound spectrum, whereas the former is thought to provide lateral inhibition that improves spectral contrast, particularly in noise. In response to pure tones, the overall discharge rate in T stellate cells is unlikely to be suppressed dramatically by D stellate cells because they respond primarily to stimulus onset and provide fast, short-duration inhibition. In vivo intracellular recordings from the ventral cochlear nucleus (VCN) showed that, when tones were presented above or below the characteristic frequency (CF) of a T stellate neuron, they were inhibited during depolarization. This resulted in a delay in the initial action potential produced by T stellate cells. This ability of fast inhibition to alter the first spike timing of a T stellate neuron was confirmed by electrically activating the D stellate cell pathway that arises in the contralateral cochlear nucleus. Delay was also induced when two tones were presented: one at CF and one outside the frequency response area of the T stellate neuron. These findings suggest that the traditional view of lateral inhibition within the VCN should incorporate delay as one of its principle outcomes.

Acoustic Stimulation↗
PubMed1983

Auditory nerve-brain stem evoked potentials in cats during manipulation of the cerebral perfusion pressure.

In order to study the effects of various degrees of cerebral ischemia on the auditory nerve-brain stem evoked potentials (BAEP), the cerebral perfusion pressure (CPP), defined as the difference between mean arterial blood pressure (MAP) and intracranial pressure (ICP), was systemically manipulated in anesthetized, paralyzed and ventilated cats. The CPP was varied by decreasing MAP, either by hemorrhage or by the infusion of a vasodilating drug, and elevating ICP by infusion of mock CSF into the cisterna magna, or by MAP depression and ICP elevation simultaneously. Even though the lower limit of adequate CPP is considered to be 40 mm Hg, the EEG became isoelectric at an average CPP of 24 mm Hg and the BAEP became isoelectric at an average CPP of 7 mm Hg. These extremely low CPP values of 7-24 mm Hg are far below the range of autoregulation of cerebral blood flow (CBF) so that the brain stem auditory pathway is still capable of generating its electrical response (BAEP) at very low CBF. This is paradoxical since these same regions of the brain have been shown to have the highest levels or regional metabolism as shown by their very high local cerebral blood flow and local glucose utilization.

Animals↗
PubMedDate not supplied

Use of the pinna reflex as a test of hearing in mutant mice.

Although it is a gross measure, the pinna reflex test is easily administered and is, therefore, incorporated as a general screening tool in mutagenesis programs. Our recent application of this approach indicated that mutant mice lacking one of the small Maf proteins, in this case MafG, failed to exhibit a pinna reflex. In contrast, littermate controls, with the same mixed 129/CD1 background, and including both wild type and heterozygous mutant animals, passed the test. Because previous studies indicate that mafG is expressed in both cochlear and vestibular parts of the mouse inner ear, the source of this 'presumed deafness' was further assessed by making round window recordings to determine compound action potential thresholds. Auditory brainstem responses were also acquired to assess function along portions of the central auditory pathway. In all cases, responses in homozygous mutants (-/-) were comparable to those obtained from littermate controls, either wild type (+/+) or heterozygous mutants (+/-). Gross anatomy of the organ of Corti was also found to be similar in all three groups of mice. Hence, the lack of a pinna reflex must relate to nonauditory causes.

Acoustic Stimulation↗
PubMed1997

Electrical and physiological changes during short-term and chronic electrical stimulation of the normal cochlea.

In the electrical stimulation (ES) of auditory pathways, the type of stimulus and the electrode/tissue interface are critical parameters for the safety and efficacy of the protocol. In this study the influence of alternate pulses, applied between round window and vertex electrodes in chronically implanted guinea pigs, and maintained during 1 and 25 daily periods of 2 h (short-term and long-term experiments, respectively), was investigated. ES consisted of monophasic current pulses of +/- 70 microA and 300 (micro)s in duration at a rate of 167/s, with alternate polarity. Compound Action Potential (CAP) audiograms, amplitudes and latencies of click-evoked CAPs, amplitudes and latencies of electrically-evoked auditory responses (EARs), and electrode impedances, were measured periodically outside or during the ES periods. Short-term ES induced no change in CAP thresholds, amplitude and latency in response to clicks at 80 dB above normal threshold, but induced a slight latency increase and amplitude decrease of the EAR, correlated with an exponential decay of the electrode impedance. On a long-term basis, CAP audiograms and latencies did not change significantly, whereas CAP amplitudes and electrode impedances increased, in correlation with each other. In control guinea pigs receiving no ES, the same CAP amplitude and impedance changes were observed over the same long-term period. The EAR and CAP changes can be explained by a variation of the electrical impedance of the electrode/tissue interface. This is possibly due to a change in electrolytes around the electrode under the influence of the ES for the short-term variation, and to an electrode encapsulation by fibrous tissue independent of the ES for the long-term change. In itself, and under the conditions of this experiment, the ES demonstrated no adverse effects on the auditory function and can be safely used for inner-ear exploration.

Acoustic Impedance Tests↗
PubMed1988

Surgical monitoring with auditory evoked potentials.

This comprehensive review of surgical monitoring with auditory evoked potentials (AEPs) includes a detailed discussion of techniques used for recording brainstem auditory evoked potentials, direct eight-nerve potentials, and electrocochleograms. The normal waveform of these different potentials is discussed, and the typical patterns of abnormalities seen with different insults to the peripheral or central auditory pathways are presented. The mechanisms most probably responsible for changes in AEPs during surgical procedures are analyzed. A critical analysis is made of what represents a significant change in AEPs. Also considered is the predictive value of intrasurgical changes of AEPs. Finally, attempts are made to determine whether AEPs monitoring can assist the surgeon in the prevention of postsurgical complications.

Audiometry, Evoked Response↗
PubMed1997

Management of vestibular schwannomas (acoustic neuromas): the value of neurophysiology for evaluation and prediction of auditory function in 420 cases.

OBJECTIVE: From 1978 to 1993, 1000 vestibular schwannomas were operated on at the Department of Neurosurgery at Nordstadt Hospital. The goal was to improve the chances of hearing preservation by recording auditory brain stem responses (ABRs). ABRs can be used for preoperative classification of cochlear nerve impairment and for prediction of the chances of hearing preservation. PATIENTS AND METHODS: In addition to the previously described audiometric testing, the patients underwent perioperative and intraoperative bilateral ABR recording at 100-dB condensation and rarefaction click stimulation. The classification system of five types of ABRs, as presented before, is based on the presence and on the latencies of Waves I, III, and V, with a special emphasis on Wave III's representing the activity of the first brain stem nuclei within the auditory pathway. According to an analysis of 420 preoperative ABRs, in case of a preoperative Type 1 or 2, the rate of hearing preservation is 80%. DISCUSSION: In the case of good clinical and audiometric hearing, a severely deteriorated ABR is mostly an indicator of severe nerve compression and adhesion by the tumor. In view of subsequently reported experiences with intraoperative ABR monitoring, the value of the presented system emphasizing the importance of Wave III is stressed and discussed with other views in the literature. The criteria presented here are not designed for recognition of retrocochlear disease but aim for evaluation of the state of the auditory nerve and its perspective. CONCLUSION: By the presented classification of ABR Type B1 through B5, preoperative prediction of the likelihood of hearing preservation is improved.

Adult↗
PubMed1998

Tinnitus in Cochlear Implant Users: The Freiburg Experience.

Cochlear implantation is a well-accepted method of aural rehabilitation in deaf or severely hearing-impaired adults and children. A majority of patients not only suffer from hearing impairment but from tinnitus. The high rate of preoperative tinnitus in adults (68.1%) stands in contrast to assumed lower rates in children. Unknown are such factors as how tinnitus develops in children, how they realize what tinnitus is, and whether the mechanism of development of tinnitus differs from that in adults, respectively. Electrical stimulation of the auditory pathway is followed by loss, or at least reduction, of tinnitus in most cases (75%). Also, the insertional trauma alone is able to stop tinnitus in some patients. Attention must be paid to the low risk of developing tinnitus postoperatively. No reports are available regarding tinnitus in children. Though younger children may not be able to report, some adolescent patients report preoperative or postoperative tinnitus (or both) that is reduced by electrical stimulation at the rates seen in adults. Further investigations are needed to define the mechanism of tinnitus development in children and to define optimal stimulation modes and rates for tinnitus reduction with best auditory performance.

Journal Article↗
PubMed1994

Prenatal and perinatal low level lead exposure alters brainstem auditory evoked responses in infants.

Wave III latency and the III-V interpeak interval of brainstem auditory evoked responses in infants in the first weeks of life decreased and increased, respectively, in association with mid-pregnancy maternal blood lead levels (2.5-35 micrograms/dl) in a group of 30 prospectively followed healthy pregnancies and deliveries. The rapid myelination of brainstem auditory pathways occurring around mid-pregnancy and the lengthening of the III-V interpeak interval with increased mid-pregnancy maternal lead suggest that brain structures involved in spatial localization of sound may be compromised by prenatal lead exposure. The data also indicate that maternal blood lead measurements during pregnancy provide an adequate surrogate index of fetal exposure.

Adult↗
PubMed1993

Pre- and postnatal development of efferent connections of the cochlear nucleus in the rat.

Although the connections of the auditory brainstem nuclei are well described in adult mammals, almost nothing is known concerning how and when these connections develop. The purpose of the present study was to describe the development of the efferent projections of the cochlear nucleus (CN), the first central relay station in the ascending auditory pathway of mammals. We used two tracers in rats aged between embryonic day 15 (E15) and postnatal day 14 (P14; birth in the rat is at E22 = P0). The carbocyanine dye DiI was applied into the CN in aldehyde-fixed tissue. The second tracer, biocytin, was applied into the ventral acoustic stria in an in vitro slice preparation. The ontogeny of the efferent projections from the CN could be divided into three periods. The first period (E15-E17) is characterized by axonal outgrowth. Axons traverse nuclei in the superior olivary complex and the lateral lemniscus and finally grow up into the inferior colliculus, but axon collaterals do not form during this period. The second period (E18-P5) is marked by pronounced collateral branching of CN fibers in auditory brainstem nuclei. Collateralisation in the contralateral inferior colliculus starts shortly before that in the ipsilateral superior olivary complex. The remaining auditory nuclei become successively innervated, as indicated by collaterals found in them. During the third period (P5-P14) terminal structures mature further, as shown by the morphological changes of the calyces of Held in the medial nucleus of the trapezoid body. In conclusion, our results show that the efferent connections from the cochlear nucleus form over a period of almost two weeks and are laid down without forming aberrant internuclear connections. On a nuclear level, an adult-like projection pattern is already achieved one week prior to the onset of physiological hearing.

Animals↗
PubMed2004

Interaural time coincidence detectors are present at birth: evidence from binaural interaction.

Binaural processing of sounds in mammals is presumably initiated within the auditory nuclei of the caudal pons. The binaural difference waveform (BD) can be derived from the sum of the waveforms evoked by right monaural clicks plus left monaural clicks minus the waveform evoked by binaural clicks. In adults, the BD's first positive peak (beta) is large only for stimuli with interaural time differences (ITDs) that produce a fused acoustic percept. Humans at birth can localize and discriminate sound sources, but their head circumference is about two-thirds of an adult head. In order to test whether beta is related to head circumference, we recorded beta in human neonates as a function of ITD. Binaural clicks with ITDs ranging between 0 and 1000 micros were used to derive BD waveforms in 34 neonates. For ITD=0, beta was detectable in 56% of newborns. The incidence of beta detection then decreased as ITD increased. Only 9% of the babies had detectable beta for all ITDs. No correlation was found between the existence of beta and other properties of the monaural or binaural auditory brainstem response. The finding that for some infants beta was present for all ITDs up to 1.0 ms suggests that there is no recalibration of brainstem delay lines with head growth. Our data suggest that the brainstem auditory pathway for detecting interaural time differences in the adult is probably present at birth. Maturational factors such as increased myelination and greater firing synchrony probably improve the detectability of beta with age. The second peak in the BD waveform (delta) was highly correlated with the existence of wave VI in the binaural and monaural waveforms.

Adult↗
PubMed1982

Pure-tone and speech intelligibility disturbances in patients with ototoxic disorders.

The prevalence and severity of hearing impairment caused by ototoxic drugs are surprisingly high. This emphasizes the importance of the questions arising from the treatment. In 33.7% of the cases, the hearing impairment caused by ototoxic antibiotics was of severe degree and in 25.4%, it was extremely severe. Parenteral, topical or oral administration of aminioglycoside antibiotics is dangerous. Because of the very poor speech intelligibility, most probably not only the spiral organ but the vestibulocochlear nerve and the higher auditory pathways are also affected by these antibiotics. In some cases, the severe distortion in sound perception cannot be compensated even by a hearing aid of the best quality, and lip-reading which was advised occasionally was without any result. To prevent these toxic effects, these drugs should be administered very parsimoniously and then under very strict conditions and close control.

Aminoglycosides↗
PubMed1996

Brainstem auditory evoked potentials (BAEPs) in tobacco smokers.

Brainstem auditory evoked potentials (BAEPs) were studied in 10 chronic male tobacco smokes (average age 26.55 years) with history of smoking 3 to 14 years to detect early subclinical impairments in auditory pathway. The values of BAEPs were compared with those of 28 age matched normal male non-smokers (control). The results revealed significant prolongation of latencies of wave I and III indicating that conductivity of sensory impulse along acoustic nerve and pons is affected in chronic smokers which may be attributed to adverse effect on myelination by nicotine and toluene present in tobacco smoke.

Adult↗
PubMedDate not supplied

Maturation of the auditory brain stem response (ABR): additional perspectives.

A retrospective, cross-sectional analysis of component latencies of the auditory brain stem response (ABR) was performed on 466 patients ranging in age from 30 weeks postconception to adulthood. The ontogeny of ABR component wave latencies was adequately described by two exponential curves having different slopes; the steeper curve represented an early, rapid maturation ending by 8 to 10 weeks post partum, and the ensuing, more gradual curve corresponded to developmental events which were completed by the beginning of the third year of extrauterine life. These observations conform to previous maturational concepts of peripheral versus central segments of the auditory pathway and to the gradual decrease in interwave latencies with increasing age. Unlike interwave latency, however, the ratio of the latencies of selected component waves was constant with increasing age. This was especially apparent in developing newborns less than 50 weeks postconception. The nonlinear bases of this phenomenon are outlined, and the insights which stem from this perspective are discussed.

Adolescent↗
PubMed2005

Vestibular schwannoma in the only hearing ear: cochlear implant or auditory brainstem implant?

OBJECTIVE: To explore the dilemma faced by neurotologists confronted with the patient who develops a vestibular schwannoma in the only hearing ear, the other having been deaf from birth, and to consider the choice between auditory rehabilitation using a cochlear implant (CI) on the congenitally deaf side and an auditory brainstem implant (ABI) on the tumor side. STUDY DESIGN: A record review of two patients born deaf in one ear and who developed a vestibular schwannoma in the contra lateral ear, who then received a CI in the congenitally deaf ear. SETTING: Tertiary referral center with special experience in vestibular schwannoma surgery, neurofibromatosis type 2 management, and cochlear implantation. RESULTS: Neither patient was a good CI user. At 1 year postimplant, they both scored 0% on abbreviated words and 0% and 7%, respectively, on Bench Kowal Bamford sentences. They scored 54% and 57%, respectively, on City University of New York sentences with lip-reading, and both had fair access to environmental sound scoring at 45% each. CONCLUSIONS: The results from cochlear implantation in the congenitally deaf ear in these patients were poor and suggest that stimulus deprivation in the early stages of the maturation of the auditory pathways is important even for a unilateral hearing loss. Unfortunately, the factors that predict a good ABI result are not known. In these circumstances, the authors advocate the insertion of an ABI at the time of tumor removal, retaining the option of CI in the congenitally deaf ear in the event of a poor outcome with the ABI.

Audiometry, Pure-Tone↗
PubMed2003

Increased wave latency in auditory brainstem response to anemia in newborn and adult sheep.

The objective of the present study was to determine whether phlebotomy-induced anemia in newborn lambs and adult sheep results in prolonged auditory brainstem response (ABR) wave latencies, and if found, whether developmental differences exist between the two groups. Among newborn lambs, hemoglobin (Hb) levels were reduced from 100-120 to 30-50 g/l over a 3-day period. Over the next 2 days, serial red blood cell transfusions were administered to restore Hb to pre-phlebotomy levels. In adult sheep, comparable levels of phlebotomy-induced anemia were achieved within a 24-hour period, after which Hb levels returned to pre-phlebotomy levels. During the induction of anemia and its reversal, a significant (p < 0.05) increase in ABR latency followed by a return to pre-anemia ABR latencies that was most prominent in the peripheral auditory pathway was observed in both newborn and adult sheep as Hb levels fell below 50 g/l (p < 0.05). There was no difference between adults and newborns in ABR latency relative to the Hb level at which ABR wave latencies increased. We speculate that ABR wave latency prolongation might serve as an indicator of the need for red blood cell transfusion.

Anemia↗
PubMed1996

Topography of auditory evoked long-latency potentials in children with severe language impairment: the T complex.

Topographic maps of the late auditory evoked potentials (AEP) were studied in a group of 20 children, aged 9-15 years, with severe language impairment (LI) and an age-matched control (C) group of 20 normal children. The stimulus was a pure tone at 500 Hz with a duration of 100 ms and a rise and fall time of 20 ms. The intensity was 75 dB HL. Six test sequences of 50 stimuli at an interval of 1.0 s were presented to the left and right ear separately. Grand average maps of all the children in the LI and the C group, separately, were calculated and showed a bilateral negativity over the temporal areas, corresponding to the negative peak of the T complex (Tb) at a latency of about 150 ms. The amplitudes were larger contralateral to the stimulated ear in both groups. A difference map between the two grand average maps showed topographic differences at temporal sites. However, the T complex could not be identified in 7 LI children and 1 C child. In the remaining subjects with a T complex the topographic pattern was similar in the two groups but with lower amplitudes and significantly longer latencies in the LI group. The presence and latency of the positive peak of the T complex (Ta) was also examined, showing significant between-group differences. The value of Tb, in diagnosing language impairment, was tested by means of a scoring system and with statistical mapping. The diagnostic sensitivity of Tb latency, amplitude and topography in selecting the LI children was 90% to 40% with a specificity of 80% to 95%. The results indicate slower and deviating processing in the central auditory pathways of LI children. The variation in results between children, with missing components or prolonged latencies in the majority, but not all, of the LI children, may be explained by different pathophysiological causes of their language impairment. The more pronounced deviations of the T complex compared with the vertex-recorded NI may also indicate a specific role of the T complex-related cortical activity in language impairment.

Adolescent↗