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PubMed1995

Topography of auditory evoked long-latency potentials in normal children, with particular reference to the N1 component.

Topographic maps of late auditory evoked potentials were obtained with the Brain Atlas III system in 34 healthy, normal hearing children aged 8-16 years. The stimulus was a 100 msec, 500 Hz tone burst, presented separately to the left and right ears, at 75 dB HL. The resulting auditory evoked potentials showed a prominent N1, after about 100 msec, and a topographic map with a corresponding fronto-lateral focus designated as the focus of N1 (FN1). Foci with varying positions and amplitudes were identified in 33 of 34 subjects after left ear stimulation and in 29 of 32 subjects after right ear stimulation. The topography showed a high degree of stability in most subjects, with the position of the negative "peak" of FN1 in front of the interaural line and with a dominance contralateral to the ear stimulated. There was a significant decrease in the latency of N1 with increasing age. FN1 tended to change position with age and some differences from adults were also observed. In conclusion, a distinct topographic pattern of the N1 component of the late auditory evoked potentials was seen in the majority of children. It remains to be established to what extent this method may be clinically useful for disclosing functional disturbances in the central auditory pathways.

Acoustic Stimulation↗
PubMed1996

Recording of brainstem evoked potentials and their association with gentamicin in neonates.

Brainstem auditory evoked potential (BAEP) recording was used to screen presymptomatically the hearing of 200 neonates treated with ampicillin (100 mg/kg daily) and gentamicin sulfate (5 mg/kg daily). The study included 130 male and 70 female neonates; post-conceptional age ranged from 34 to 57 weeks (mean 42.36 weeks). We divided neonates into 2 groups according to duration of antibiotic treatment; group 1 consisted of 179 patients who were treated with antibiotic agents for < or = 7 days. Although 15 (8.4%) in this group initially manifested abnormal BAEP recordings, only 8 of these brain-damaged neonates (4.5%) (6 with peripheral and 2 with central dysfunction) later manifested abnormal recordings. Group 2 consisted of 21 neonates who were treated for 10 to 30 days; BAEP recordings were abnormal in 7 patients (33.3%) (4 with peripheral and 3 with central dysfunction). We conclude that BAEP is indicated only for neonates treated with gentamicin sulfate for > 10 days. In this group, infants so treated usually have underlying disease or severe infection, including birth asphyxia, hypoxia, sepsis, and meningoencephalitis, all of which are clinically significant indicators of high risk for auditory pathway dysfunction.

Anti-Bacterial Agents↗
PubMed2002

Processing of interaural temporal disparities in the medial division of the ventral nucleus of the lateral lemniscus.

The medial division of the ventral nucleus of the lateral lemniscus (VNLLm) contains a specialized population of neurons that is sensitive to interaural temporal disparities (ITDs), a potent cue for sound localization along the azimuth. Unlike many ITD-sensitive neurons elsewhere in the auditory system, neurons in the VNLLm respond only at the onset of tones. An onset response may be significant for behavior because, under echoic conditions, tones require sharp onsets for accurate localization. In contrast, noise can generally be localized even with gradual onsets, presumably because transients occur at random intervals in noise. We recorded responses of neurons in the VNLLm to tones and noise in unanesthetized rabbits. We found that although tones elicited a transient response, noise elicited a sustained response as if it was a sequence of transients. The responses to tones indicate that these neurons represent a secondary stage in the processing of ITDs. The onset response to tones was only weakly synchronized to the phase of the tone, indicating that neurons in the VNLLm inherit their sensitivity to ITDs from their inputs. The latencies were short (~8 ms), implying that the ITD sensitivity is derived from ascending inputs. Most neurons in the VNLLm discharged maximally at the same ITD at all frequencies, a characteristic shared with neurons of the medial superior olive. However, the latency of neurons in the VNLLm to interaurally delayed stimuli is linked strongly to the timing of the contralateral stimulus. This suggests that these neurons receive a suprathreshold, contralateral input that is modulated by a subthreshold input conveying information about ITDs. Other stations in the auditory pathway contain a subset of neurons that respond transiently to tones and are sensitive to ITDs. These neurons may represent a novel pathway that assists in localizing sounds in the presence of reflections.

Acoustic Stimulation↗
PubMed2003

Impairments in dichotic listening in patients presenting anterior communicating artery aneurysm.

Impaired dichotic listening has been documented in numerous etiologies, but there is limited information on patients who present with anterior communicating artery (ACoA) aneurysm. The sequelae following ACoA aneurysm is frequently associated with neurobehavioral impairments, such as confabulation, memory, and behavior, as a result of the areas of innervation (DeLuca, 1992; DeLuca & Diamond, 1995). Clinical experience, however, shows ACoA aneurysm to also be associated with impairments in dichotic listening. Participants in this study were divided into 2 groups: patients who presented with ACoA aneurysm with age-matched controls, and patients who presented moderate to severe traumatic brain injury (TBI) with age-matched controls. TBI patients were included for test-validity purposes and to allow a comparison between diffuse and focal cerebral damage. Dichotic listening results revealed a similar pattern for patients with ACoA aneurysm and those with brain injury. The findings suggest that central auditory pathways are susceptible to damage following ACoA aneurysm.

Adult↗
PubMed1991

Visual evoked and brain stem auditory evoked potentials in divers.

Visual evoked potentials (VEP) were examined in 14 divers during dives to 360 metres of seawater (msw). All latencies increased significantly with depth. VEP and brain stem auditory evoked potentials (BAEP) were similarly examined in 18 divers before and after these dives. N75 was significantly increased after compared to before the dive, while there was no significant difference in the P100 and N145 latencies. BAEP I-V latency was significantly decreased after the dives. VEP and BAEP were examined in 156 divers and 99 controls. There was no significant difference in VEP. BAEP I-III interpeak latency was significantly increased for the divers, but with no significant changes in I-V and III-V latencies. VEP and BAEP were examined in 26 divers after treatment for neurological decompression sickness. There was no significant difference compared to the control group. The conclusions are that VEP and BAEP change transitorily with influence of hyperbaric pressure, but do not measure major permanent disturbances in the divers' visual and auditory pathways.

Adult↗
PubMed1991

Visual and brainstem auditory evoked potentials in hereditary motor-sensory neuropathy.

Visual evoked potentials (VEP) and brainstem auditory evoked potentials (BAEP) were recorded in 57 children and adults with hereditary motor-sensory neuropathy (HMSN); 37 of them were diagnosed as type I (demyelinating) and 20 as type II (axonal). None of the patients presented central nervous system involvement. The results were compared with VEP and BAEP records of 12 adults with Guillain-Barré syndrome (GBS) and 40 healthy controls. Above 30% of all patients with HMSN I showed delayed latency of the VEP. These abnormalities were less expressed in HMSN II. Abnormal BAEP were observed in almost 50% of patients with HMSN I and HMSN II with nearly the same frequency in both types but more pronounced in HMSN I. The most common feature was prolongation of the I-III interpeak latency (JPL). The VEP and BAEP changes could be present simultaneously in the same patient (mainly in HMSN I) or separately. More often the abnormalities were observed in the adult patients. Normal VEP and BAEP values were present in all patients with GBS. The results strongly suggest the subclinical optical and auditory pathways involvement in HMSN patients.

Adolescent↗
PubMed1988

[Contribution of cochlear acoustic emissions in pediatric audiology].

A new method is described for pediatric otologic exploration : cochlear acoustic emissions (CAE), and results reported of CAE recordings in 15 children with normal hearing and 31 infants at otoneurologic risk, suspected of having moderate or severe hypoacusia on conventional audiometry. Results were compared with those obtained by study of V wave threshold of AEP. The incidence of CAE in children and infants with normal hearing was 100%, the absence of CAE being related to a V ware threshold of AEP of 30 dB nHL or more. The CAE threshold is closely related to that of the V wave of AEP. The use of CAE, a rapid, non-invasive, objective audiometric method, could be a first line screening technic allowing separation, within several minutes, of a normal hearing population from one with a lesion of transmission or endocochlear apparatus with CAE V wave threshold of over 30 dB nHL. In addition, in children with a flat AEP the CAE allows study of the cochlear independently of auditory pathways.

Adolescent↗
PubMed1990

Effect of contralateral sound stimulation on the distortion product 2F1-F2: evidence that the medial efferent system is involved.

The mechanical nonlinearity of the cochlea that is associated with normal cochlear function, induces distortion products that can be recorded in the external auditory canal. The acoustic cubic distortion product 2F1-F2 (DP) was measured in the external canal in the presence and in the absence of a contralateral white noise. The experiments were carried out on 20 guinea pigs after a section of the middle ear muscles. They showed that the presence of a contralateral white noise induces a significant reversible reduction of the magnitude of the DPs. This suppressive effect produced by the contralateral white noise was completely canceled out by the midline sagittal section of the brainstem. This report supports the hypothesis that the suppressive effect of a contralateral sound stimulation is mediated by the medial efferent system.

Acoustic Stimulation↗
PubMed1996

Neurometamorphosis of the ear in the gypsy moth, Lymantria dispar, and its homologue in the earless forest tent caterpillar moth, Malacosoma disstria.

The adult gypsy moth, Lymantria dispar (Lymantriidae: Noctuoidea) has a pair of metathoracic tympanic ears that each contain a two-celled auditory chordotonal organ (CO). The earless forest tent caterpillar moth, Malacosoma disstria (Lasiocampidae: Bombycoidea), has a homologous pair of three-celled, nonauditory hindwing COs in their place. The purpose of our study was to determine whether the adult CO in both species arises from a preexisting larval organ or if it develops as a novel structure during metamorphosis. We describe the larval metathoracic nervous system of L. dispar and M. disstria, and identify a three-celled chordotonal organ in the anatomically homologous site as the adult CO. If the larval CO is severed from the homologue of the adult auditory nerve (IIIN1b1) in L. dispar prior to metamorphosis, the adult develops an ear lacking an auditory organ. Axonal backfills of the larval IIIN1b1 nerve in both species reveal three chordotonal sensory neurons and one nonchordotonal multipolar cell. The axons of these cells project into tracts of the central nervous system putatively homologous with those of the auditory pathway in adult L. dispar. Following metamorphosis, M. disstria moths retain all four cells (three CO and one multipolar) while L. dispar adults possess two cells that service the auditory CO and one nonauditory, multipolar cell. We conclude that the larval IIIN1b1 CO is the precursor of both the auditory organ in L. dispar and the putative proprioceptor CO in M. disstria and represents the premetamorphic condition of these insects. The implications of our results in understanding the evolution of the ear in the Lepidoptera and insects in general are discussed.

Animals↗
PubMed2001

Early bilateral deafening prevents calretinin up-regulation in the dorsal cortex of the inferior colliculus of aged CBA/CaJ mice.

This study was conducted to test the hypothesis that age-related calretinin (CR) up-regulation seen in the dorsal cortex of the inferior colliculus (ICdc) of old hearing CBA mice is dependent upon neural activity within the auditory pathway. We tested this hypothesis by bilaterally deafening young CBA/CaJ mice with kanamycin, and then aging them until 24 months. This manipulation mimics the lack of sound-evoked auditory activity experienced by old C57BL/6J mice, who are deaf and do not show CR up-regulation with age. Cell counts revealed that the density of CR+ cells in the ICdc of old hearing CBA mice was statistically different from old deafened CBA mice raised under identical conditions. Old hearing CBAs possessed an average of 27.54 more CR+ cells/100 microm2 than old deafened CBAs. When old deafened CBAs were compared to young hearing CBAs, young hearing C57s, and old deaf C57s, there was no significant difference in mean CR+ cell density in ICdc. Thus, only the old normal hearing CBAs showed an increase in CR+ cells with age, supporting the hypothesis that CR up-regulation depends upon sound-evoked activity. Moreover, these results demonstrate that up-regulation of CR expression was not simply due to a mouse strain difference.

Aging↗
PubMed2003

Autism and auditory brain stem responses.

OBJECTIVE: To study a controversy that has been discussed for more than two decades: whether or not children with autism have abnormalities affecting the cochlear nerve or the auditory pathway in the brain stem and, if so, to describe these abnormalities. DESIGN: A group of 153 children and adolescents with autistic disorder were included in an investigation of auditory brain stem responses (ABR). Two thirds of this group, 101 individuals (75 boys, 26 girls), had normal hearing and they were selected for an in-depth ABR study. The results from the study group were compared with those of an age-matched comparison group. RESULTS: The III-V interpeak latency (IPL) was significantly prolonged in both boys and girls with autism, compared with the controls. The latencies of ABR waves I and V were also significantly lengthened in the study groups. The individual test results showed that more than half of this normal-hearing autistic disorder group (58%) had abnormalities of one or more of eight ABR parameters studied. The most common abnormalities were prolongation of wave V (38%), and of I-V IPL (28%). A lengthening of the I-V IPL was also recorded in 27% of 49 children who were difficult to test or who had hearing loss. Abnormal left-right differences of ABR latencies were found in 18% of autism cases with normal hearing. CONCLUSIONS: Possible causes of the reported ABR abnormalities, observed here as well as in other studies, are discussed. Brain stem lesion, occult cochlear dysfunction, and involvement of the cochlear efferent system are probable factors that can explain the ABR findings

Adolescent↗
PubMed1998

Successful prevention of retrocochlear hearing loss in murine experimental allergic encephalomyelitis with T cell receptor Vbeta8-specific antibody.

Experimental allergic encephalomyelitis is an animal model of a T cell-mediated autoimmune disease -- for example, multiple sclerosis. We demonstrated that mice with experimental allergic encephalomyelitis developed retrocochlear hearing loss, and that the lesion of the auditory pathway might be related to T cell receptor Vbeta8-expressing T cells. To investigate whether anti-Vbeta8 antibody could prevent hearing loss, we carried out brain stem auditory evoked potential testing, histologic examinations, and flow cytometry in antibody-treated and control myelin basic protein-immunized B10.PL mice. The antibody was administered just before immunization of myelin basic protein. The disease incidence and severity were significantly reduced in the mice injected with the antibody. The results of brain stem auditory evoked potential testing, histologic examinations, and flow cytometry indicated that the depletion of Vbeta8-expressing T cells brings the prevention of hearing loss, as well as prevention of other neurologic deficits. The development of T cell receptor-specific antibody therapy might help treat retrocochlear hearing loss in multiple sclerosis.

Animals↗
PubMed2003

Mid latency and slow vertex responses during pregnancy.

Central auditory pathways picked up electro-physiologically as mid latency responses (MLRs) and slow vertex responses (SVRs) have been studied least in women during their critical periods of life although auditory brainstem responses (ABRs) have been studied by many researchers. In the present study MLRs and SVRs were recorded in 20 pregnant women of age group 18-28 years. Their period of gestation ranged between 26-40 weeks and pregnancy had been uneventful and normal. MLRs and SVRs were recorded from Cz-A1 and Cz-A2 positions with alternating 90 dB sound pressure click stimuli delivered at 5 Hz and 0.5 Hz respectively. 256 stimuli for mid-latency and 64 stimuli for slow vertex responses were averaged and analyzed. Different waves of these auditory evoked responses were compared with 20 age matched non-pregnant females. The data obtained was analyzed for each variable by using unpaired student's T test. Present study did not reveal any difference in MLR waves during pregnancy when compared with the non-pregnant females whereas all the SVR waves were found to be significantly delayed in pregnant females. As SVR generators are found in different cortical areas, it can be said that auditory information processing at the higher centers is slow during pregnancy which in turn could be due to elevated levels of sex hormones specially estrogen and progesterone during pregnancy.

Acoustic Stimulation↗
PubMed2000

Calcitonin gene-related peptide suppresses hair cell responses to mechanical stimulation in the Xenopus lateral line organ.

The presence of calcitonin gene-related peptide (CGRP) in the efferent fibers of virtually every hair cell organ studied suggests it may serve some fundamental but heretofore unknown role in control of hair cell function. We examined the effects of CGRP on spontaneous and stimulus-evoked discharge patterns in an in vitro preparation of the lateral line organ of Xenopus laevis. Discharge patterns were determined by sinusoidally displacing the cupula with a glass micropipette driven with a piezoelectric device while recording afferent fiber activity. All afferent fibers had characteristic frequencies of 16-32 Hz. Responses synchronized to cupular displacements as small as 20 nm. CGRP suppressed responses of the lateral line organ to displacement while increasing spontaneous discharge rate. In the presence of CGRP, stimulus-response curves were shifted 10 dB toward higher displacement levels. The suppression of stimulus-evoked responses suggests a function for CGRP as an efferent neurotransmitter that is similar to that of cholinergic efferent transmission in other hair cell organs. The 10 dB shift toward larger displacements makes it comparable in magnitude with the effects of electrical stimulation of efferents in the mammalian cochlea. This suggests a significant role for CGRP in efferent modulation of the output of this mechanosensory organ.

Acoustic Stimulation↗
PubMed1987

Neurologic, audiologic, and electrophysiologic sequelae of bilateral temporal lobe lesions.

A 67-year-old woman with demonstrated intact peripheral and brain-stem auditory pathways presented with sudden deafness secondary to sequential bilateral temporal lobe infarcts. Initial examination revealed no behavioral response to sounds and a mild Wernicke's aphasia. Hearing gradually returned but auditory agnosia persists. Changes seen on the computed tomographic scan and the middle latency auditory evoked response over a seven-month period were analyzed and suggest that the peak component of the middle latency response arises from Heschl's gyrus.

Aged↗
PubMed1991

Hereditary motor and sensory neuropathy (HMSN) and optic atrophy (HMSN type VI, Vizioli).

Clinical and electrophysiological findings are described in three patients with hereditary motor and sensory neuropathy in association with optic atrophy (HMSN VI). The optic atrophy was of the Leber type in a 15-year-old boy. In a 70-year-old patient, as in three members of his family, optic atrophy was associated with tapetoretinal degeneration. In addition to HMSN and optic atrophy a 20-year-old man suffered from sensorineural deafness. Electrophysiological studies indicated a neuronal form of neuropathy, as in HMSN II. Brainstem auditory evoked potentials also revealed subclinical involvement of the central auditory pathways in the patients without hearing defects.

Adolescent↗
PubMed1992

Auditory-evoked brainstem responses in the hibernating woodchuck Marmota monax.

1. This study measured the changes in the auditory-evoked brainstem responses in the woodchuck (Marmota monax) during hibernation and arousal. 2. The auditory brainstem response of the euthermic woodchuck consisted of four waves occurring in a 10 msec time window after stimulation. 3. In the hibernating woodchuck, waves I and II could be traced down to the lowest body temperatures. 4. As temperatures increased all the components of the ABR emerged. The latencies of all the waves showed systematic decrease with temperature increments, the effect being cumulative across the time window. 5. These findings reflect activity in the VIIIth cranial nerve and the cochlear nuclei during hibernation and restoration of the functional integrity of the brainstem auditory pathway during arousal.

Animals↗