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PubMed1980

Auditory prostheses--a challenge for neurophysiology.

To achieve speech discrimination with prosthetic stimulation, pre-processing of speech adapted to the function to be replaced is indispensable. This is demonstrated using the example of a phase-conserving frequency transposition for a more efficient use of residual hearing. The intelligibility of transposed speech was investigated by employing simulated residual hearing. Long-term implanted electrodes in the auditory nerve of the cat permitted both the measurement of the natural activity of fibres and the application of corresponding stimulus currents. Phase reversal of the acoustic input was used to isolate a phasic response with a topographically differing proportional or differential behaviour. This suggests a periodicity analysis of the sound in the auditory pathway. In acoustic and electrical stimulation, additionally implanted, cortical control electrodes revealed largely corresponding potentials; the dynamic stimulation ranges, however, differed greatly. Finally, the possibility of assessing speech perception by measuring speech-evoked potentials is discussed.

Cochlear Implants↗
PubMed1999

Thalamic asymmetry is related to acoustic signal complexity.

Hemispheric asymmetries in response to speech sounds are well documented. However, it is not known if these asymmetries reflect only cortical hemispheric specialization to language or whether they also reflect pre-conscious encoding of signals at lower levels of the auditory pathway. This study examined differences in neural representations of signals with acoustic properties inherent to speech in the left versus right side of the thalamus. Specifically, 2000 Hz tone bursts, clicks and synthesized forms of the phoneme /da/ were presented to anesthetized guinea pigs. Evoked responses were recorded simultaneously from aggregate cell groups in the left and right medial geniculate bodies. Results showed an asymmetric response to complex auditory stimuli between the left versus right auditory thalamus, but not to the simple tonal signal. Moreover, asymmetries differed in male versus female animals.

Acoustic Stimulation↗
PubMed1982

Neurophysiological studies in adrenomyeloneuropathy. A report on five cases.

Neurophysiological studies were performed in 5 patients in two families suffering from adrenomyeloneuropathy (AMN). The diagnosis was supported by electron microscopy of nerve twigs in all cases and by the demonstration in 2 cases of increased levels of saturated very long chain fatty acids in cultured fibroblasts (Moser, personal communication). Measurements of the sensory-motor conduction velocities demonstrated the variability of the peripheral nerve damage in AMN, further confirmed by quantitative studies of sensory nerve biopsies. Somatosensory evoked potentials (SEP) were abnormally delayed and their configuration was abnormal, mainly following stimuli applied to the lower limbs. Our data suggest a more severe involvement of the fasciculus gracilis and an extension of the lesions to the medial lemnisci in agreement with the few postmortem reports showing multifocal demyelination. Brain stem auditory evoked potentials (BAEP) were delayed, pointing towards lesions between cochlear nerve and superior olivary nucleus and also at lateral lemniscal level. Morphological confirmation is lacking but the close topographical relationship between the secondary auditory pathways and the medial lemnisci indicates that even small lesions could damage simultaneously both pathways. Neurophysiological studies contribute to the diagnosis of AMN, they confirm the inter- and intrafamilial variability of the clinical features and help to explain the signs and symptoms of this condition.

Adrenal Insufficiency↗
PubMed1981

The use of kainic acid for studying the origins of scalp-recorded auditory brainstem responses in the guinea pig.

Kainic acid was injected into the medial nucleus of the trapezoid body (MNTB) of guinea pigs to evaluate its use in studying generator loci of the scalp-recorded auditory brain stem response (ABR). Sound-evoked near-field potentials from the MNTB and far-field ABRs were recorded before, during and up to 2 h after the injections. Two hours post-injection, small amounts of kainic acid (0.25 nmol in 0.1 microliters of Ringer solution) resulted in neuronal destruction which histologically appeared confined to the MNTB. Larger amounts (10 nmol in 1.0 microliters) produced more extensive lesions. Regardless of the dose of kainic acid, near-field activity evoked by contralateral ear stimulation was almost totally abolished and ABR wave III amplitude was reduced by as much as 60%. In future studies, the use of excitotoxic amino acids to produce lesions within complex nuclear subdivisions of the auditory pathway may yield valuable information as to the relative contributions that brainstem structures make to the various waves comprising the ABR and about the behavioral effects that axon sparing lesions produce.

Acoustic Stimulation↗
PubMed2005

Recording click-evoked myogenic potentials (CEMPs) with a setup for brainstem auditory evoked potentials (BAEPs).

AIM OF THE STUDY: Click-evoked myogenic potentials (CEMPs) originate in the sternocleidomastoid (SCM) muscle through a reflex loop involving the sacculus and the vestibular nerve. In this study we suggest that they can be picked up from the mastoid reference used for auditory evoked potential (AEP) recording by using standard filters for brainstem AEPs (BAEPs). They consist of a P13-N20 complex. METHODS: Fifty normal subjects were investigated. Recordings were performed with the same setting as that used for conventional BAEPs but without artifact rejection and using a wide time window (100 ms). Unilateral auditory stimulations were used. All acquisitions were performed in both sitting and supine positions. In nine subjects CEMPs and BAEPs were simultaneously recorded at both earlobe and both SCM muscles. RESULTS: In all subjects, a CEMP P13-N20 component could be evidenced in sitting, but not in supine position at both the ipsilateral earlobe and the ipsilateral SCM muscle. Its latency was 0.7 ms lower at the earlobe. It obeyed the same relationship to stimulus intensity at both earlobe and SCM muscle. CONCLUSION: These results demonstrate the possibility to get simultaneous information on the brainstem auditory pathways and on a reflex probably mediated through the sacculus and the vestibular nerve. Further studies on patients with selective vestibular nerve impairment should be conducted to confirm the clinical utility of this approach.

Adult↗
PubMed1991

[Cerebro-oculo-hepato-renal syndrome (Arima's syndrome) with slowly progressive renal insufficiency and epilepsy].

We reported an additional case of Arima's syndrome with slowly progressive renal insufficiency and epilepsy. The patient is a 20-year-old man whose parents are consanguineous. He had a history of mild asphyxia at birth, and unexplained tachypnea developed during the neonatal period. But it disappeared later, and he have had no respiratory problem since then. Physical examination on admission at the age of 19 years revealed bilateral blephaloptosis, narrow palate, searching nystagmoid movement, absence of light reflex, muscle hypotonia and wasting of extremities. Funduscopic study showed optic hypoplasia, choroid coloboma and narrowing of vessels. Head CT scan showed agenesis of cerebellar vermis and hypoplasia of brainstem. CT scan and echography of the kidney disclosed the bilateral multiple cysts. Liver was hyperechoic in echographic study; this finding is consistent with fatty change. EEG showed dysrhythmic slow wave activity with sporadic spike and wave complex. Compared with previously reported cases, the present case has the following features: (1) slowly progressive renal insufficiency, (2) generalized tonic clonic convulsion developing from the age of 11 months, (3) ABR abnormalities including the right-sided shortening of wave I-II interpeak latency and bilateral ill-defined wave V. Slow progress of renal failure in our case may reflect the mild pathological process of the kidney with sparing functional nephrons. It shows the diversity of the kidney pathology in Arima's syndrome. Epilepsy is a less common association in the syndrome, whereas EEG abnormalities were reported. ABR abnormalities may reflect the morphological alteration of the brainstem structure including auditory pathway. In our case it is uncertain whether the neonatal tachypnea was due to birth asphyxia or brainstem malformation responsible for abnormal respiration as suggested in Joubert's syndrome.

Adult↗
PubMed1990

Auditory evoked responses in awake rabbits after exposure to high intensity noise impulses.

Impulse noise effects were tested in chronic experiments on 8 awake rabbits. Alterations of cochlear potentials and evoked responses from the inferior collinulus and the medial geniculate body were studied. The rabbits were subsequently exposed to 10 noise impulses of 144 dB SPL, then (after recovery) to 10 impulses of 153 and 164 dB SPL. After exposure the amplitudes of all potentials were reduced. Time of restitution depended on the intensity of the noise, the restitution failed after exposure to 164 dB SPL impulses. Time lapses of the amplitude-reduction and restitution process were comparable for both structures of the auditory pathway. The peak latencies were prolonged significantly in only two of the rabbits after this impulse intensity. Impulses of 164 dB SPL were followed by irreversible changes of all evoked responses.

Acoustic Stimulation↗
PubMed1985

Auditory middle latency responses in children: effects of age and diagnostic category.

The nature of auditory middle latency responses (MLRs) in children has been the subject of considerable debate. In order to study MLRs as a function of age, MLRs were obtained in 217 subjects ranging in age from 6 days to 20 years, all with normal auditory brain-stem responses (ABRs). Subjects were classified into several diagnostic categories: normal; communicative disorders (language delay, learning disability); mentally retarded, multiply handicapped; and post-meningitic. Age effects, the effects of diagnostic category, and possible differences in MLRs of males vs. females and right vs. left ears were examined. The detectability of both Na and Pa was found to increase significantly as a function of age. Detection of these MLR components became similar to adult values (approaching 100% detectability) at approximately 10 years of age. No significant differences were found among diagnostic categories. There were also no significant differences in the detectability of MLRs in males as compared to females, and there were no right vs. left ear differences. The strong age effect which appears to exist in the MLR influences their clinical use. When responses are present, they may be useful indicators of hearing sensitivity, but the absence of MLRs in children cannot be taken as an indication of hearing loss. Similarly, absent or abnormal MLRs cannot be interpreted as a manifestation of auditory pathway dysfunction, since there appears to be little difference in MLRs in normal subjects and MLRs in patients with a wide range of neurologic, cognitive, and speech and language disorders.

Adolescent↗
PubMed1991

Brain-stem auditory evoked responses in 56 patients with acoustic neurinoma.

The brain-stem auditory evoked responses (BAER's) recorded from 56 patients with acoustic neurinomas were analyzed. Ten of the patients had intracanalicular tumors and 46 had extracanalicular tumors. It was possible to obtain BAER's following stimulation of the affected side in 28 patients and after stimulation of the unaffected side in all 56. Five patients (11%) had normal BAER's following stimulation of both sides; three of these patients had intracanalicular tumors. Among BAER's obtained following stimulation of the affected ear, the mean interpeak latency (IPL) for peaks I to III associated with extracanalicular tumors was significantly prolonged relative to controls (p less than 0.001), and linear regression analysis revealed a significant positive correlation between tumor size and IPL of peaks I to III (p less than 0.05). Analysis of the 56 BAER's recorded after stimulation of the unaffected side revealed a significant positive correlation between the IPL's of peaks III to V and tumor size (p less than 0.001). This correlation was not strengthened when accounting for the degree of brain-stem compression. Finally, evidence of preserved function within the auditory pathway, even in the presence of partial hearing loss, is presented. This finding suggests that more patients might benefit from surgical procedures that spare the eighth cranial nerve.

Cranial Nerve Neoplasms↗
PubMed2002

The effects of a connexin 26 mutation--35delG--on oto-acoustic emissions and brainstem evoked potentials: homozygotes and carriers.

The purpose of this study was to examine whether outer hair cells (OHCs), inner hair cells and the brainstem auditory pathway are impaired due to a mutation in a gap junction protein, connexin 26 (Cx26), 35delG. Fifty-six individuals, from a village with widespread consanguinity and profound, non-syndromic congenital deafness, due to 35delG mutation, were selected among relatives of deaf people. The individuals were either non-carriers (n=20), heterozygous (n=20) or homozygous (n=16) for the mutation. Distortion product oto-acoustic emissions (DPOAEs) and auditory brainstem evoked potentials (ABEPs) in mutation non-carriers, in heterozygotes (carriers) and in subjects homozygous for the mutation were compared in addition to audiometric evaluation. Most deaf homozygotes had no DPOAEs, except some sporadic responses at 1000, 8000 and 10000 Hz. This was also observed in audiometry which showed profound hearing loss in most cases. Two cases were unique: one had moderate to severe hearing loss and the other had severe to profound hearing loss. A significant difference was found between non-carriers and carriers of 35delG: non-carriers had larger DPOAE responses than heterozygotes at all frequencies. The prevalence of responses got lower with higher frequencies in both groups, but between 6000 and 10000 Hz 50-70% of the carriers had no DPOAE responses, compared to 30-60% of non-carriers. In both groups responses diminished with age, but no significant interaction was found between age and the genetic group. ABEPs among homozygotes were variable: in most homozygotes ABEPs were absent or partial (waves III, V) with prolonged latencies, but two subjects had ABEPs within normal limits, in one ear. ABEPs were normal with no differences between carriers and non-carriers. We suggest that OHC function is affected by the 35delG mutation in Cx26. In addition, the hearing of carriers of this mutation may be impaired at very high frequencies (8000-10000 Hz), which are not assessed in routine audiometry or ABEP testing.

Adolescent↗
PubMed1975

Organization and development of brain stem auditory nuclei of the chicken: organization of projections from n. magnocellularis to n. laminaris.

The tonotopic and topographic organization of the bilateral projection from second-order auditory neurons of nucleus magnocellularis (NM) to nucleus laminaris (NL) was examined in young chickens. In one group of birds, the NM axons which innvervate the contralateral NL were severed by cutting the crossed dorsal cochlear tract at the midline. Heavy terminal degeneration in NL was confined to the neuropil area immediately ventral to the perikaryl lamina. Very little degeneration was seen in the dorsal neuropil region. In a second series of animals, the charactertistic frequency (CF) of cells in an area of NM was first determined by microelectrode recording techniques and then a small electrolytic lesion was made through the recording electrode. Following survival periods of 24-48 hours, the distribution of projections from the lesioned area to the ipsilateral and contralateral NL was examined using the Fink-Heimer method. As previously described in the pigeon, projections from NM terminate densely in the neuropil region immediately dorsal to the ipsilateral NL cell bodies and ventral to the perikaryl layer on the contralateral side, providing each NL neuron with segregated binaural innervation. Lesions in any area of the NM produced degeneration confined to a limited caudo-rostral and medio-lateral portion of both laminar nuclei. To investigate this topographic relationship, the cuado-rostral extents of the lesion in NM and of the resulting degeneration in both NL were determined. Linear regression and correlation analyses then related these positional values to each other and to the CF found at the center of each lesion. All correlations were highly significant and ranged from 0.78 between the position of the lesion in NM and CF to 0.91 between the caudo-rostral position of degeneration in the NL ipsilateral and contralateral to the lesion. It is concluded that neurons in NM project in a very discrete topographic, tonotopic and symmetrical fashion to NL on both sides of the brain, contributing to the binaural response properties and tonotopic organization of neurons in NL. The results also suggest that the organization of projections from NM to NL could provide a mechanism for the differential transmission delay required by a "place" model of low-frequency sound localization.

Animals↗
PubMed1989

Auditory brainstem responses in ground squirrels arousing from hibernation.

Auditory brainstem responses (ABRs) were recorded in ground squirrels (Citellus lateralis) arousing from hibernation. Squirrels implanted with recording screws to record ABRs, and a thermistor to record brain temperature, were placed in a cold room at 9 degrees C on a 2L:22D light-dark cycle. Hibernating animals were moved from the cold room and ABRs recorded during arousal. The responses showed a gradual development of all brainstem peaks. At low temperatures there were very long latencies to the peaks. The amplitudes of the peaks increased (with fluctuations) as brain temperature increased. The data indicate that neural generators on the brainstem auditory pathway were all activated early in arousal. These results do not support the hypothesis that successive peaks appear and grow in amplitude only after previous peaks are fully developed.

Acoustic Stimulation↗
PubMed1994

Brain-stem auditory evoked responses to hypercarbia in preterm infants.

To determine the effect of acute hypercarbia on brain-stem function in preterm neonates, we compared brain-stem auditory evoked responses (BAERs) during 8% CO2 breathing to those elicited during room air breathing in 12 healthy preterm infants during the first week of life. End-tidal CO2 (ETpCO2), respiratory rate and depth were monitored throughout the protocol. Absolute wave latencies and interpeak intervals of the BAERs were analyzed from duplicate trials. During 8% CO2 breathing, ETpCO2, respiratory rate and depth of respiration increased significantly (P < 0.05). The absolute latency of wave V was prolonged (P < 0.025) in the hypercarbic state as compared to baseline. Interpeak interval III-V was also prolonged (P < 0.025). Values of absolute peak latencies I and III were unaffected by the hypercarbic state. These data demonstrate that elevations in pCO2 which elicit ventilatory responses also effect the BAER. The specific effects on ventilatory pattern, peak V latency and interpeak interval III-V indicate brain-stem responsiveness and alterations in the more central components of the auditory pathway. These findings raise important considerations regarding the influence of hypercarbia on brain-stem function in preterm infants and the clinical management of such infants with abnormalities of gas exchange.

Administration, Inhalation↗
PubMed2006

Seeing sounds: visual and auditory interactions in the brain.

Objects and events can often be detected by more than one sensory system. Interactions between sensory systems can offer numerous benefits for the accuracy and completeness of the perception. Recent studies involving visual-auditory interactions have highlighted the perceptual advantages of combining information from these two modalities and have suggested that predominantly unimodal brain regions play a role in multisensory processing.

Animals↗
PubMed1982

Auditory brainstem response (ABR) in infantile Gaucher's disease.

The auditory brainstem response (ABR) was studied in an infant with Gaucher's disease. The infant was normal until the age of three months. His illness began with stridor, strabismus, inguinal hernia and failure to thrive. Thereafter, muscular rigidity with opisthotonus, ocular palsies, difficulty in swallowing and respiratory failure due to central origin developed. He died of respiratory failure due to central origin developed. He died of respiratory failure at the age of one year and four months. The ABR was abnormal at six and eight months of age. Initially, at the age of six months, there was a lengthening of the peak latencies of wave I, II and III and disappearance of the waves after IV. But at eight months, more marked lengthening of the peak latencies of the waves and the disappearance of waves after III were noted as his general condition deteriorated. The autopsy revealed relative preservation of the nuclei and tracts of the auditory pathways in the brainstem. The ABR was useful for monitoring the progress of the disease in this patient because it made detection of brainstem lesions possible.

Adult↗
PubMed1997

Comparative study of sound localization and its anatomical correlates in mammals.

One of the fundamental features of hearing is the ability to localize the sources of sounds, particularly brief sounds, which may warn of nearby animals. Yet not all mammals localize sound equally well with threshold acuity ranging from about 1 degree for elephants and humans to more than 25 degrees for gerbils and horses and a near absence of localization in some subterranean species. During the past decade evidence has accumulated that this variation cannot be accounted for simply by the availability of the physical cues for locus. Nor does it appear to be a function of an animal's lifestyle. Rather sound-localization acuity in mammals appears to be a function of the precision required of the visual orienting response to sound. Thus the neural integration of hearing and vision in cortex, as well as in multimodal subcortical structures, is a reflection of their behavioral integration and evolutionary coupling.

Animals↗
PubMed1979

Acoustically evoked potential: dependence upon age.

The slow components of the potentials evoked acoustically by pure tones (1 kHz, 0 to 90 dB HL) were compared between two groups of subjects. All subjects of one group were 22 years old; the members of the other group had an average age of 63 years. The P2-latencies of the older subjects were significantly shorter for 60, 75 and 90 dB HL than those of the younger group. This finding was interpreted as a sign of a decreased efferent inhibition of several nuclei of the auditory pathway in the older subjects. No significant difference between the two groups could be found for the amplitudes (N1/P2), the exponent of the intensity function, or the latencies of P1 and N1.

Acoustic Stimulation↗
PubMed1988

The use of brain stem auditory evoked potentials in the evaluation of the central nervous system.

Brain stem auditory evoked potentials (BAEPs) are sensitive to anatomic disturbances of the brain stem auditory pathways, especially those caused by disruption of myelin. They are influenced by temperature but are virtually unaffected by level of consciousness, drugs, and metabolic disequilibrium. These properties make BAEPs useful in evaluating many posterior fossa disorders.

Acoustic Stimulation↗