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PubMed1997

[Effects, on early auditory evoked potentials, of road traffic noise, of benzodiazepine and their combination].

In this study, 30 young men and 30 young women (with the same proportion of anxious persons in each group) were submitted, in random order, to: i) a road traffic noise of 75 dBA for 15 min; ii) this same noise for 15 min, having ingested 0.25 mg of alprazolam (Xanax*) 1 h before; iii) uniquely 0.25 mg of alprazolam. The auditory brainstem evoked potentials (ABEP) were taken before and after exposure to noise (for the non-noise case, we respected the same time schedule). The alprazolam had an effect on the cochlea and can be considered as a noise adaptation factor on the auditory pathways explored by the ABEP.

Acoustic Stimulation↗
PubMed2006

Early maturation of evoked otoacoustic emissions and medial olivocochlear reflex in preterm neonates.

The present study was designed to investigate the early maturation of the brainstem regulation of the cochlear function in preterm neonates. Evoked otoacoustic emissions (EOAE) and their regulation via the medial olivocochlear efferent (MOC) reflex were investigated in a large population of preterm neonates and compared with full-term neonates and young babies from birth to 4 y and school-aged children. In 28-wk preterm neonates, EOAE were seen in the mid-frequency range. These responses extended both to the low (down to 1025 Hz) and high (up to 6152 Hz) frequency ranges at 38 wk of gestational age and remained stable up to 4 mo. At this stage, the amplitude of EOAE overlapped adult values. EOAE amplitudes then decreased to reach adult values at 3 y of age. Maturation of MOC efferents innervating the outer hair cells was investigated by studying the suppressive effect of contralateral sound on the EOAE amplitudes (MOC reflex). The first MOC responses were recorded in preterm neonates of 32-33 wk of gestational age, reaching adult-like values at 37 wk of gestational age. The maximum effect of MOC efferent activation occurred between 2000 and 4000 Hz. These results suggest that, in humans, MOC efferents mature in utero. Thus, testing the MOC reflex may have a clinical relevance to detect an abnormal development of the auditory pathways, particularly of a brainstem circuitry not explored through conventional testing.

Child, Preschool↗
PubMedDate not supplied

[Auditory evoked potentials in individuals over 50 years].

BACKGROUND: auditory evoked potentials. AIM: to describe the results of brainstem auditory evoked potentials (PEATE), middle latency auditory evoked potentials (PEAML) and cognitive potential (P300) in individuals over 50 years. METHOD: this study was developed at the Speech and Hearing Investigation Laboratory in Auditory Evoked Potentials of the Speech-Language and Hearing Course of the Department of Physiotherapy, Speech-language and Hearing Sciences and Occupational Therapy of FMUSP. Twenty four subjects (45 ears) were evaluated through PEATE and P300, and only 18 of these subjects (36 ears) were evaluated through PEAML. All subjects had ages between 51 and 74 years and were divided in three groups: GI (50-59 years), GII (60-69 years) and GIII (70-79 years). All subjects presented either normal hearing or neurossensorial hearing loss of a moderate-severe level in the PEATE, and of a moderate level in the PEAML and in the P300. The frequency range evaluated in the PEATE and in the PEAML varied from 3000 to 6000Hz, while in the P300 it varied from 1000 to 1500Hz. For the statistical analyses of the data, the Kruskal-Wallis test, the Mann-Whitney test and the two proportion equality test were used. RESULTS: significant statistical differences were simultaneously observed between the groups for the interpeak I-V in the PEATE and for the Na wave latency in the PEAML - in the PEATE the difference was caused by GIII and in the PEAML it was caused by GI. A statistically significant difference between the groups was observed for the latency of the P300 component. Considerable alterations were also found regarding the quality of the responses of the auditory evoked potentials, indicating a strong correlation between the deterioration of the responses and the increase in age. CONCLUSION: the aging process of the auditory system progressively affects the auditory pathways throughout the brainstem and temporal lobe.

Age Factors↗
PubMedDate not supplied

Nerve growth factor serum level is reduced in patients with sensorineural hearing impairment: possible clinical implications.

Nerve growth factor (NGF) is the first and best characterised member of a family of neurotrophic factor. NGF is produced by numerous cells and it is present in physiologically relevant amounts in the bloodstream. It is known to promote the survival of peripheral sensory neurons and can be potentially useful as a therapeutic agent in neuronal system. On the both these observations we based our hypothesis that low circulating NGF might lead to sensorineural hearing loss (SNHL). To address this question we measured the levels of NGF in the bloodstream of patients affected by SNHL. The results showed that the amount of circulating NGF in these patients is significantly lower compared to levels found in patients not affected by this deficit. The results of the present study demonstrated that NGF might be a useful candidate for preventing the damage and promoting recovery or degeneration of the auditory pathways in humans.

Adolescent↗
PubMed2004

Characteristics of electrically evoked potentials in patients with auditory neuropathy/auditory dys-synchrony.

The primary goal of this study was to compare the characteristics of the post-implant evoked potentials with preimplant evoked potentials in patients with auditory neuropathy (AN) or dys-synchrony. AN is typically characterized by sensorineural hearing loss, reduced speech perception, abnormal temporal processing, and unusual patterns of results with various objective audiological tests. In some cases, these patients may be appropriate candidates for a cochlear implant. In this article, we highlight evoked potential findings in two children diagnosed with AN who were provided with multichannel cochlear implants. Preoperative, interoperative and postoperative evoked potential measures show that the restoration of neural synchrony may occur at multiple levels of the auditory pathways in patients with AN when appropriate diagnostic tests, cochlear implantation and rehabilitation are provided.

Acoustic Impedance Tests↗
PubMed1994

[An experimental study of the auditory brainstem implant in guinea pigs].

In order to examine the characteristics of the auditory brainstem implant, an animal model with electrical stimulation of the cochlear nucleus in guinea pigs was created. Middle latency response (MLR) to pulsatile electrical stimulation of the cochlear nucleus was recorded from the auditory cortex with bipolar plantinumiridium electrodes and stereotaxic technique. The electrically and acoustically generated MLRs have a similar morphology though there are little differences in the latencies, wave intervals and dynamic ranges. The results indicated that the central auditory pathways can be activated by means of electrical stimulation. The safety of the brain tissue to the electrical stimulation are also discussed.

Acoustic Stimulation↗
PubMedDate not supplied

The neonate has a temporary conductive hearing loss due to fluid in the middle ear.

Postnatal functional changes in the activity of the ear and auditory pathway in neonatal guinea pigs [from day of birth (postnatal day, PND = 0), PNDs 1-4, 7 and then weekly up to 7 weeks] were studied as a model of maturation of hearing in human neonates. On the day of birth there were signs of a conductive hearing loss: negative middle ear pressure, auditory nerve brainstem evoked response (ABR) threshold elevation, ABR wave 1 latency prolongation and low amplitude otoacoustic emissions. The conductive hearing loss is probably a result of the (amniotic) fluid found in the neonatal middle-ear cavity. Over the next PNDs, this conductive hearing loss was resolved. In order to confirm this neonatal conductive hearing loss and its resolution, saline was instilled into the middle ear of guinea pigs. This induced signs of a conductive hearing loss similar to those seen in the neonatal guinea pigs which disappeared with clearance of this fluid. Therefore it may be concluded that most of the changes in auditory function seen over the first PNDs are due to absorption of amniotic fluid from the middle-ear cavity.

Acoustic Impedance Tests↗
PubMed1976

Endogenous perioxidatic activity in brain stem neurons as demonstrated by their staining with diaminobenzidine in normal squirrel monkeys.

In order to test for the presence or absence of endogenous peroxidatic activities within the brains of normal squirrel monkeys, sections from the brain stems were incubated in buffered media of diaminobenzidine (DAB) and hydrogen peroxide, according to the methods of Graham and Karnovsky20 or Novikoff and Goldfischer39. It was found that neurons within certain regions were consistently stained by both mediamthese reactive neurons belong to the extrapyramidal motor system (globus pallidus, substantia nigra (pars diffusa), red nucleus, pontine and mesencephalic reticular formation), to certain cranial nerve nuclei (oculomotor, trochlear, abducens, mesencephalic trigeminal, vestibular) and to relay nuclei of the auditory pathway (superior olivary nucleus and nucleus of the trapezoid body). Neurons within other regions of the brain stem, such as thalamus, hypothalamus and corpus striatum were not stained. On the other hand, the neuropil, excluding the neurons, in other motor areas (such as the subthalamic nucleus, inferior olivary nucleus and corpus striatum) and other auditory relay nuclei (inferior colliculus, nucleus of lateral lemniscus) were also significantly stained. Processes around the Purkinje cells of the cerebellum were particularly reactive. Under the electron microscope, reaction products were localized prominently along the cristae and limiting membranes of the mitochondria and within peroxisome-like bodies of the stained neurons. Non-reactive neurons have little or no reaction products in their organelles. The staining was absent when DAB was withheld, and it was weak or absent if H2O2 was omitted from the media. The addition of inhibitors of catalase, 3-amino-1,2,4-triazole and 2,6-dichlorophenolindophenol did not affect the staining intensity, whereas the addition of potassium cyanide, a strong inhibitor of metalloenzymes, especially heme-enzymes, almost completely abolished the reactions. In addition, a 3-day 'bleaching treatment' with 30% H2O2 did not affect the reactions. These results suggest that the reactivity in the above regions was due not to neuromelanin or other pigments, but rather to heme-enzymes and/or other hemoproteins. It was postulated that a higher concentration of the reactive agents was characteristic of certain neuronal types in the brain stem of the squirrel monkeys, and could be related to the cells' functional needs, energy requirements and perhaps to the metabolism of their specific neurotransmitters.

3,3'-Diaminobenzidine↗
PubMed2003

Association of chronic and current measures of lead exposure with different components of brainstem auditory evoked potentials.

Current blood lead (PbB) affects brainstem auditory evoked potentials (BAEPs) in children but whether a similar association exists in lead-exposed adults remains unclear. During an investigation of the neurobehavioral effects of occupational lead exposure we performed BAEPs on 359 English- and French-speaking, currently exposed, male, lead smelter workers having a mean (S.D.) age of 41 (9.0) years, employment duration of 17 (7.9) years, PbB of 28 (8.4)microg/dl, working-lifetime weighted average blood lead (TWA) of 39 (11.9) microg/dl, and working-lifetime integrated blood lead (IBL) index of 719 (421.0) microg.year/dl, the latter a measure of cumulative lead dose. BAEPs were performed at a click stimulation of 10s(-1) for 1000 repetitions, at an intensity 75dB above the threshold of the ear tested. Right-sided latencies for peak waves I, III, and V and the corresponding interpeak intervals (IPI) I-V, I-III, and III-V were chosen for analyses. Age correlated significantly with BAEPs, PbB, TWA, and IBL. Partial correlation analyses adjusting for age found PbB and TWA significantly associated with wave I latency r=0.13, P<0.01 and r=0.11, P<0.05, respectively, and IBL significantly associated with wave III latency r=0.16, P<0.01. The contribution of age, PbB, TWA and IBL to the variances of different BAEPs was assessed using multiple regression analysis. In the regression model of the full group, after the contribution of age, PbB and TWA accounted for significant variance of wave I, Deltar(2)=1.8, P<0.01 and Deltar(2)=1.2%, P<0.04, respectively, and IBL accounted for significant variance of wave III latency, Deltar(2)=2.8%, P=0.00 and I-III interpeak interval, Deltar(2)=1.4%, P<0.03. Four groups similar in age were created with increasing abnormalities based upon clinical cut-off scores for wave I latency and I-V interpeak interval. PbB, TWA, and IBL were significantly higher in the group with abnormalities of both latency in wave I and IPL I-V. Lead exposure interferes with BAEPs in a dose-dependent manner. Current lead exposure in this population of lead smelter workers preferentially affected conduction in the distal auditory nerve while chronic lead exposure appeared to impair conduction in the auditory nerve and the auditory pathway in the lower brainstem.

Acoustic Stimulation↗
PubMed2000

[Auditory neuropathy].

INTRODUCTION: Auditory neuropathy is a type of neurosensorial hypoacusis that produces significant impairment in language comprehension. Etiologically, this neuropathy has been related to perinatal hypoxia, hyperbilirubinemia, metabolic disorders and degenerative entities that affect the auditory pathway. PATIENTS AND METHODS: We report five children with this disorder. Two of the children were referred for otorhinolaryngeal assessment after failing the neonatal hearing screening and one was referred because of a history of perinatal hypoxia. The two eldest children were referred because of schooling problems and language impairment. In all the children, auditory brainstem response, otoacoustic emissions, tympanometry stapedius reflex were examined and liminal and condition-orientation reflex audiometry were performed. After diagnosis, the children were followed-up for 3 consecutive years. RESULTS: In all five children, tympanogram and otoacoustic emissions were normal. The stapedius reflex and auditory brainstem responses with 80-90 dli stimuli were absent. Medium latency and conical and cognitive potentials were normal in the only child (aged 9 years) in whom they could be performed. In two children (aged 7 and 9 years), verbal discrimination was within the normal range for theft age. In all the children, audiometry revealed bilateral mild-to-moderate hypacusla, which did not change during follow up. CONCLUSIONS: Auditory neuropathy can be detected by the combined use of neonatal hearing screening techniques, auditory brainstem responses and otoacoustic emissions. Interest in the early identification and diagnosis of this disorder Is due to the clear benefit to language development secondary to the early treatment and rehabilitation of these children.

Age Factors↗
PubMed1985

Brainstem auditory evoked responses in hereditary spinocerebellar ataxias.

Brainstem auditory evoked responses were recorded in 18 patients with spinocerebellar ataxia, seven with Friedreich's ataxia, four with late-onset cerebellar degeneration, and seven with olivopontocerebellar atrophy. All patients had normal hearing. BAERs were abnormal in 10 cases (58%). Five of the seven patients with Friedreich's ataxia (71%) had grossly abnormal BAERs with wave I only being identified. Five of the patients with olivopontocerebellar atrophy (71%) had abnormal BAERs, whereas all patients with cerebellar degeneration had normal BAERs. The results indicate abnormalities of the brainstem auditory pathways in patients with spinocerebellar ataxias and show that the test is of value in the differential diagnosis of this group of disorders.

Adolescent↗
PubMed2005

[Physiopathological mechanisms in tinnitus generation and persistence].

Progress in neuroscience research has given birth to new theories for tinnitus generation. From a point of view where cochlear dysfunctions would be considered as the origin and maintenance mechanisms, it has been introduced the important role of compensation systems from the central auditory pathways. They could act as the most relevant factor for chronic persistent tinnitus after a peripheral aggression. Unmasking of silent synapses or sprouting of new ones activate cortical reorganization for frecuencial areas nearby the non-stimulated ones through brain plasticity. Connections to associative cortex and limbic-amigdala area using the non-classical auditory system explain the presence of hyperacusis, anxiety or depression, factors that increase the severity of tinnitus. Implementation of these physiopathological theories reinforces the tinnitus neurophysiological model. The development of an aversive response through the survival reflex and the participation of negative emotional response are the responsible for signal persistence and vegetative reactions from the autonomous nervous system. Implications of this knowledge for tinnitus treatment involve the central auditory system approach through the combination of medical counselling for reduction of the aversive reaction and sound therapy to diminish its perception.

Cochlea↗
PubMed2006

Organic solvents and hearing loss: The challenge for audiology.

Organic solvents have been reported to adversely affect human health, including hearing health. Animal models have demonstrated that solvents may induce auditory damage, especially to the outer hair cells. Research on workers exposed to solvents has suggested that these chemicals may also induce auditory damage through effects on the central auditory pathways. Studies conducted with both animals and humans demonstrate that the hearing frequencies affected by solvent exposure are different to those affected by noise, and that solvents may interact synergistically with noise. The present article aims to review the contemporary literature of solvent-induced hearing loss, and consider the implications of solvent-induced auditory damage for clinical audiologists. Possible audiological tests that may be used when auditory damage due to solvent exposure is suspected are discussed.

Animals↗
PubMed1995

A comparison of binaural interactions using traditional and maximum length sequence evoked response paradigms.

OBJECTIVE: Two paradigms, the traditional binaural interaction (BI) paradigm and a maximum length sequence (MLS) BI paradigm were evaluated to investigate BI effects. DESIGN: Evoked response BI effects were assessed at different levels of the auditory pathway in two experiments. Each experiment consisted of three conditions: a traditional BI paradigm using conventional stimuli, a traditional BI paradigm using MLS stimuli, and a MLS BI paradigm using MLS techniques to recover kernels reflecting BIs. Eleven normal-hearing young adults served as subjects. RESULTS: There was evidence for BI effects on the auditory evoked brain stem response (ABR) and the middle latency response (MLR) using the traditional BI paradigm and conventional stimuli. With the same paradigm and MLS stimuli there was evidence for BI effects on the MLR but not the ABR. The more robust conventional effects may be explained by the larger amplitude evoked responses recorded conventionally due to the slower stimulation rates and more efficient signal to noise enhancement. BI effects were observed for both the ABR and MLR by recording BI kernels in the MLS BI paradigm. CONCLUSIONS: MLS BI kernels can be recorded in normal hearing adults. The MLS BI paradigm offers three potential advantages in recording binaural effects; avoidance of some of the methodological problems associated with traditional BI paradigms, faster stimulus rates permitting a more complete characterization of binaural rate effects, and more rapid data collection.

Acoustic Stimulation↗
PubMed1984

Effects of halothane or enflurane with controlled ventilation on auditory evoked potentials.

The effects of increasing concentrations of halothane and enflurane on selected components of the auditory evoked response were studied in 12 patients; six received halothane and six enflurane. After the induction of anaesthesia with thiopentone, anaesthesia was maintained with 70% nitrous oxide in oxygen. Ventilation was controlled. The inspired concentration of the inhalation agent was increased incrementally, halothane in steps of 0.5% up to 2.5%, and enflurane in steps of 1% up to 5%. With both agents, linear dose-related increases were seen in the latencies of waves III, V, Pa and Nb and the interpeak intervals I-V and III-V, with decreases in the amplitudes of Pa and Nb. In five of the patients the inhalation agent was discontinued at the end of the test period, resulting in reversal of the changes in some or all of these waves. End-tidal carbon dioxide tension was controlled and variations of temperature and arterial pressure were insufficient to produce the observed changes. The results show that halothane and enflurane delay neural transmission along the brainstem and cortical sections of the auditory pathway and that the effects of these agents are approximately related to their known anaesthetic potencies.

Adolescent↗
PubMed1990

[Auditory brainstem response and somatosensory evoked potential in Machado-Joseph disease in Japanese families].

To clarify physiological aspects of Machado-Joseph disease (MJD), we studied auditory brainstem response (ABR) and somatosensory evoked potential (SEP) in 17 clinically diagnosed patients with MJD aged 32-64 in Japanese families. ABR was recorded in 13 patients. In 8 patients, ABR were abnormal. In 5 patients, the latency of I wave was normal, but other waves could not be evoked. In the other 3 patients, I-III interpeak latency was prolonged. SEP was recorded in 15 patients. In SEP of median nerve, 11 patients had abnormal findings, and SEP of posterior tibial nerve revealed abnormal findings in all 15 patients. In all patients, responses from Erb's point and popliteal fossa were normal in latency, but other peaks were low in amplitude or absent, and the latency and central conduction time (CCT) were prolonged. The result of ABR indicated the involvement of the brainstem auditory pathways in MJD, and the result of SEP suggested that somatosensory pathways, particularly central pathways, would be involved in the disease process. ABR and SEP can be potential diagnostic methods for detection of subclinical abnormality in MJD patients.

Adult↗
PubMed2006

Modulation of steady-state auditory evoked potentials by cerebellar rTMS.

Steady-state auditory evoked responses (SSAER) obtained via electroencephalography (EEG) co-vary in amplitude with blood flow changes in the auditory area of the cerebellum. The aim of the present EEG study was to probe the cerebellar role in the control of such SSAER. For this purpose, we investigated changes in SSAERs due to transient disruption of the cerebellar hemisphere by repetitive transcranial magnetic stimulation (rTMS). SSAERs to click-trains of three different frequencies in the gamma-band (32, 40 and 47 Hz) were recorded from 45 scalp electrodes in six healthy volunteers immediately after 1-Hz rTMS and compared to baseline SSAERs assessed prior to magnetic stimulation. Cerebellar rTMS contralateral to the stimulated ear significantly reduced the amplitude of steady-state responses to 40-Hz click-trains and showed a tendency to reduce the amplitude to 32-Hz click-trains. No effects were observed for 47-Hz click-trains, nor for magnetic stimulation of the cerebellum ipsilateral to auditory stimulation or after sham stimulation. Our results suggest that interference with cerebellar output by rTMS modifies functional activity associated with cortical auditory processing. The finding of maximum effects on 40-Hz SSAERs provides support to the notion that the cerebellum is part of a distributed network involved in the regulation of cortical oscillatory activity and points at some frequency-specificity for the control of auditory-driven neuronal oscillations.

Acoustic Stimulation↗
PubMed1983

A study of some of the ascending and descending vestibular pathways in the pigeon (Columba livia) using anterograde transneuronal autoradiography.

A mixture of tritiated proline and fucose was injected into the endolymph of one of the membranous labyrinths of each of 5 white king pigeons (Columba livia). The membranous labyrinth was resealed and the animals were allowed to survive for 15 days. Brains and upper parts of the spinal cords were sectioned and processed by standard autoradiographic procedures. Clear labeling was noted in structures usually associated with both the ascending auditory pathways and the ascending and descending vestibular pathways. Vestibular structures ipsilateral to the injected labyrinth which contained heavy labeling were Scarpa's ganglion and all 6 vestibular nuclei. No labeling was noted in the contralateral Scarpa's ganglion and sparce, if any, labeling was noted in the contralateral vestibular nuclei. Contralateral structures associated with ascending vestibulo-ocular pathways which contained heavy labeling were the medial longitudinal fasciculus, abducens nucleus, trochlear nucleus, and two parts of the oculomotor nucleus--the dorsolateral part and the ventromedial part. Less heavily labeled ipsilateral vestibulo-ocular-related structures included the medial longitudinal fasciculus, abducens nucleus and the ventrolateral edge of the trochlear nucleus. The dorsomedial part of the oculomotor nucleus was heavily labeled on the side ipsilateral to the injected labyrinth. Slight, if any, labeling was noted in either the ipsilateral or contralateral brachium conjunctivum or regions corresponding to the mammalian ascending tract of Deiters. The medullary core of most folia but primarily the medullary core and granular areas of folia IX and X of the cerebellum were labeled.(ABSTRACT TRUNCATED AT 250 WORDS)

Afferent Pathways↗