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At least 1,207 records · Page 67Linked to original sources
PubMed1997

[Diagnostic importance of middle latency auditory evoked potentials (MLAEP) in multiple sclerosis].

This study was aimed at assessing the interest of middle latency auditory evoked potentials (MLAEP) recordings in multiple sclerosis (MS). Brainstem auditory evoked potentials (BAEP) and MLAEP were recorded in 40 control subjects and 65 patients who had MS according to Poser's criteria. Na and Pa latencies were significantly delayed in the MS group. These abnormalities were detected in 60% of the patients. In 26% of the cases with normal BAEP, abnormalities of MLAEP were present. In 71% of the patients abnormalities of both BAEP and MLAEP were observed. These results suggest the ability of MLAEP recordings to detect lesions of the auditory pathways rostral to the pons and show the value of their combined recordings in MS patients.

Adult↗
PubMed2004

The effects of L-carnitine on presbyacusis in the rat model.

Reactive oxygen metabolites are products of oxidative metabolism that are continuously generated in vivo, and are known to produce serious cellular, tissue and genomic damage. l-carnitine is an endogenous amine that has been shown to have an effect on the synthesis of reactive oxygen metabolites. Twenty Wistar rats, 24 months of age, were randomly assigned to two groups as control and l-carnitine treatment groups. One millilitre of distilled water was administered to control rats and 50 mg/kg l-carnitine to rats of l-carnitine treatment groups by intragastric gavage once a day for 30 days. At the end of 30 days, all groups underwent auditory brainstem response testing after administration of intraperitoneal urethane anaesthesia. l-carnitine treatment reduced III, V latencies and I-III, III-V and I-V interpeak latencies (IPL) significantly compared with the control group. l-carnitine treatment improved age-related deterioration in auditory pathways and hence may be a new alternative for the treatment of presbyacusis.

Aging↗
PubMedDate not supplied

Speech sound representation, perception, and plasticity: a neurophysiologic perceptive.

Historically, auditory research has focused predominately upon how relatively simple acoustic signals are represented in the neuronal responses of the auditory periphery. However, in order to understand the neurophysiology underlying speech perception, the ultimate objective is to discover how speech sounds are represented in the central auditory system and to relate that representation to the perception of speech as a meaningful acoustic signal. This paper reviews three areas that pertain to the central auditory representation of speech: (1) the differences in neural representation of speech sounds at different levels of the auditory system; (2) the relation between the representation of sound in the auditory pathway and the perception/misperception of speech, and (3) the training-related plasticity of speech sound neural representation and speech perception.

Auditory Cortex↗
PubMed2000

Brainstem auditory evoked potential responses in iron-deficient anemic children.

Iron deficiency is a major health problem in developing countries manifesting not only as overt anemia but also involving the CNS resulting in cognitive and behavioral deficits. Iron is an important nutrient and essential element involved in myelin formation and neurotransmitter synthesis and thus contributes to normal neurological activity. Hypomyelination has been reported in iron deficient states with possible neural conduction defects. The brainstem auditory evoked potential response is used extensively to identify lesions associated with various demyelinating diseases and hence has been used in the present study to observe the effect of iron deficiency on sensory brain function. A trend of increased absolute and interpeak latencies and reduced amplitudes of the waves leading to a definite linear correlation between the severity of anemia and the degree of neurophysiological deficit suggests a subclinical involvement of the auditory pathway in the brainstem of iron deficient children.

Adolescent↗
PubMed1990

Brainstem auditory evoked potentials (BAEPs) in pregnant women.

The electrophysiological correlate of change in sensory function during pregnancy has not been reported. The brain stem auditory evoked potentials were recorded in eight pregnant women during third trimester from CZ-A1 and CZ-A2 position, with alternating 90 dB sound pressure click stimuli delivered at 10/sec and -40 dB (white noise) masking of contralateral ear. Two thousand and forty eight responses were analysed and replicated. The noise and other artefacts were rejected with filter bandpass setting 150 to 3000 Hz. The evoked responses in pregnant women were compared with ten age matched normal subjects using Student's 't' test. The threshold for eliciting wave V of the brainstem auditory response was higher in pregnant women (28.1 +/- 2.1 dB). The absolute peak latencies of waves I to V were similar in both groups. However, Inter peak latencies (IPLs) I-III, III-V were on higher side in the pregnant women, and I-V, in particular (3.9 +/- 0.14) was significantly higher when compared with controls (3.73 +/- 0.16). These findings suggest that besides an increase in evoking wave V threshold, neural conduction process in brainstem auditory pathways during pregnancy is also delayed within + 2SD of the mean central conduction time in nonpregnant state.

Adult↗
PubMed1981

On the use of natural stimuli in neurophysiological studies of audition.

Close scrutiny of the conceptual base which supports a recent explosion of interest in biologically relevant stimuli reveals several gaps and examples of inconsistent terminology. It is apparent that selection of stimuli has not always been optimal, in the sense that relevance was undefined and controls were lacking. The neurophysiological evidence most often sought has been the response of single neurons in central auditory pathways, and presentation of these results has at times made progress difficult to discern. A simplified, testable version of the feature detector hypothesis is discussed.

Acoustic Stimulation↗
PubMed2006

[A case of infarction in brainstem and cerebellum as a initial symptom with bilateral hearing loss].

A 56-year old male presented with a sudden onset of bilateral hearing difficulty. He complained of dizziness and gait disturbance at the onset and subsequently developed bilateral hearing loss and tinnitus. Brain MRI revealed multiple infarcts in bilateral middle cerebellar peduncles, bilateral cerebellar hemispheres and the right cerebral peduncle. Three dimentional computed tomography angiography (3D-CTA) showed severe stenosis of bilateral vertebral arteries. Infarcts were located in the border zone between anterior inferior cerebellar artery (AICA) and superior cerebellar artery (SCA), suggesting hemodynamic infarctions. Auditory brain stem responses (ABR) were recorded three times. The initial ABR demonstrated all waves except for wave I on day 14. Wave I on the left was normal, while wave I peak latency on the right was prolonged. On day 61, all waves were recorded, although peak latencies of waves III to V and interpeak intervals of the wave I to III on the right side were prolonged. Involvements of the cochlear nerve and pontine auditory pathway were suggested from the ABR abnormalities in this case.

Anterior Cerebral Artery↗
PubMed1991

Plasticity of auditory maps in the brain.

The central auditory pathway contains maps of sound frequency that reflect the functional organization of the cochlea, as well as topographic representations of other stimulus features, such as sound location, that are synthesized within the brain. Both types of map undergo changes during development and are shaped by experience. This is particularly true of the representation of auditory space in the superior colliculus, which can be modified by alteration of auditory and visual inputs early in life. Although experience-induced plasticity in this map is restricted primarily to the developmental period, the frequency representation in the cortex of adult animals can re-organize following partial deafness.

Acoustic Stimulation↗
PubMed1975

The auditory cortical projections onto the medial geniculate body in the cat. An experimental anatomical study with silver and autoradiographic methods.

The auditory cortical projections to the medial geniculate body (MGB) were studied in the cat. Lesions carefully restricted to each one of the subdivisions of the auditory and peri-auditory cortex were made and degenerating fibres were mapped in the MGB. In other experiments L-[4-5-3-H]leucine was injected into the cortex of AI, AII and SF and its transport to the MGB was studied by autoradiography. The results show that fibres arise in the deep layers of the cortex of AI, pass through the deep subdivision of the dorsal nucleus of the MGB as well as through the magnocellular MGB. and end in the pars lateralis of the ventral nucleus of the MGB, Arising from AII, axons pass through the magnocellular MGB and end in the superficial and deep subdivisions of the dorsal nucleus extending to the most caudal part of the MGB. The ectosylvian posterior auditory cortex projects diffusely to all subdivisions of the MGB as well as to its magnocellular part. Of the peri-auditory areas, only the suprasylvian fringe projects to the parvicellular MGB, and it sends axons to the dorsal nucleus of the MGB. The SF and the ectosylvian anterior periauditory area send fibres to the magnocellular MGB. The insular cortex does not project to the MGB but sends heavy projections to lower nuclei of the auditory pathway. The complementary use of degeneration and autoradiographic methods shows that each method may be used to eliminate the drawbacks of the other. This strategy appears as being most adequate for the study of reciprocal projections such as those found between the MGB and the three auditory areas AI, AII, and the ectosylvian posterior auditory area.

Animals↗
PubMed1996

On determinants of first-spike latency in auditory cortex.

The first-spike latency of neurones at any level of the auditory pathway decreases with stimulus amplitude. As stimuli are generally shaped with rise functions to avoid spectral splatter, a common interpretation of the latency decrease is that the amplitude of the signal reaches the neurone's firing threshold earlier during the rise time. We demonstrate here, for auditory cortex neurones and by varying the amplitude and rise time of tonal stimuli, that this threshold model is inadequate to account for the observed latency changes, particularly when adaptive processes are taken into account. The data raise the possibility that latency may be a function of other properties associated with a signal's onset, such as rate of change of peak pressure.

Acoustic Stimulation↗
PubMedDate not supplied

Results of cochlear implantation in patients with severe to profound hearing loss--implications for patient selection.

In patients with some residual hearing and minor benefit from conventional hearing aids, the benefits of cochlear implantation have to be weighed carefully against eventual adverse effects. In this study, pre- and post-operative thresholds as well as functional results after cochlear implantation are reported; 17 of 44 implanted adults had residual hearing pre-operatively (mean threshold(250 to 4000 Hz): 106 dB HL) in the implanted ear. Residual hearing in the implanted ear could not, in general, be preserved post-operatively. Seventeen of 44 implanted children had some amount of residual hearing in the implanted ear pre-operatively (implanted ear: 114 dB HL; contralateral ear: 109.9 dB HL; mean thresholds(250 to 4000 Hz))). Contrary to the results in adults, residual hearing in the implanted ear remained statistically unchanged. Hearing in the contralateral ear increased significantly from 109.9 to 101.9 dB HL post-operatively. This increase was mainly attributed to maturation of the central auditory pathway. In adults with residual hearing, the monosyllable word recognition scores increased significantly from 9 per cent pre-operatively to 42 per cent post-operatively. Children with residual hearing tended to perform better on speech-related test material compared to children without prior auditory experience. Cochlear implantation is indicated in adults and children with residual hearing and minor benefit from conventional amplification. The contralateral ear in children should be considered for additional acoustical stimulation.

Adult↗
PubMed1981

Scalp distribution of the auditory evoked brainstem potentials in the guinea pig during monaural and binaural stimulation.

Auditory evoked brainstem potentials in response to monaural and binaural sound stimuli were observed by monopolar recording at five positions on the skull of the guinea pig. With monaural presentation the amplitudes of the first two potentials in the complex had a maximum at ipsilateral positions, the third potential was of uniform size at all recording positions, and the fourth and fifth potentials were largest at contralateral positions. The differing maxima of the negative and positive components of the individual potentials proved to be consistent with the theory of volume conduction. When sounds were presented binaurally the amplitudes of all potentials were symmetrical with respect to the vertex. Moreover, binaural interactions at the neural level could be inferred from the brainstem responses. The results indicate that the individual potentials in the complex are associated with activation of specific structures in the auditory pathway. This finding and the observed differences between the two sound modes have implications for clinical practice.

Acoustic Stimulation↗
PubMed1988

Brainstem auditory evoked potentials to different stimulus rates in parkinsonian patients.

Twenty-five Parkinson's disease (PD) patients were studied by brainstem auditory evoked potentials (BAEP) with increased stimulus rate (ISR) and compared to a control age and hearing matched group. A second comparison was made between L-dopa-treated and untreated PD patients. The results of the study suggest that there is subclinical involvement of the auditory brainstem in PD patients, possibly due to the dopamine influence upon the blood vessels. Our results also indicate that dopamine is probably not involved in the synaptic transmission along the auditory pathway of the brainstem.

Aged↗
PubMed2005

Specific findings in distortion product otoacoustic emissions and growth functions with chronic tinnitus.

Chronic tinnitus has a very high prevalence in industrialized countries. Latest studies found chronic tinnitus in 4% of the German population, with almost 2% suffering severely in their daily life. Because no curative therapeutic approach is available--neither pharmacological nor surgical--the main focus lies in treatments that enhance the habituation of tinnitus. Habituation occurs in almost 50% of affected patients as a normal process, leading to a complete compensation. This finding is based on the ability of the auditory perception to habituate random noise and focus on important acoustic information. According to our audiological data, 90% of tinnitus patients have deficits in inner-ear function as a generator of tinnitus, mainly in the outer hair cells. This occurrence can be verified by registration of distortion products of otoacoustic emissions. Thus, the main origin of tinnitus is peripheral, and most patients suffer from accompanying hearing loss, even though it is sometimes mild or subjectively not even noticed. In almost 50% of our patients, we find hyperfunction of outer hair cells, again recorded via distortion products of otoacoustic emissions and their growth functions. Normal efferent reduction of distortion products through contralateral acoustic stimulation does not take place in most tinnitus patients. This finding shows that central auditory functions are also disturbed in chronic tinnitus patients, leading to reduced efferent effects on the hair cells and thus impeding habituation. Tests to verify these more central pathological findings have yet to be developed. We have data on diminished ability to distinguish stimuli from random noise by bilateral sound processing: The so-called bilateral masking difference test results are pathological in almost 30% of patients suffering from chronic tinnitus. We concluded from our audiological data that chronic tinnitus is primarily a cochlear dysfunction, but habituation is impeded by accompanying or consecutive deficits of the central auditory pathway. Regarding therapeutic approaches, these central functions can be trained by hearing therapy, as we know from patients' rehabilitation.

Adolescent↗
PubMedDate not supplied

Cortical activity evoked by a multichannel cochlear prosthesis.

We have recorded electric potentials and neuromagnetic fields evoked by electric stimulation of the auditory nerve in a totally deaf patient with an implanted multichannel prosthesis. The evoked electric responses were a vertex-negative deflection at about 70 ms after stimulus onset and a vertex-positive deflection at about 180 ms. Evoked magnetic responses coinciding with the vertex potential were found in the right hemisphere, ipsilateral to the stimulated ear. The equivalent source of these responses corresponds to activation of the right auditory cortex. In the left hemisphere, the magnetic responses were considerably smaller and less reliable. These results suggest an abnormality of the central auditory pathways in this patient. In the future, neuromagnetic recordings might be used preoperatively to forecast the effectiveness of the possible implantation.

Auditory Cortex↗
PubMed1995

[Clinical usefulness of auditory brainstem responses in patients with sensorineural and mixed hearing loss].

The brain stem response (ABR) and pure tone audiometry was recorded in to patients: 23 with sensorineural and 17 with mixed hearing loss. The control group included 10 males and 10 females. The presented method (ABR) shows to be very useful for objective estimating the level of hearing lose and location of failure in auditory pathways. Particular statistics analysis of obtained results (wave V latency-intensity function) shows high correlation with a pure tone audiometry.

Adolescent↗
PubMed2002

[The influence of haemodialysis on hearing organ of children with chronic renal failure].

Haemodialysis applied in terminal phase of chronic renal failure causes considerable metabolic and electrolyte disturbances within a few hours in human organism. The aim of the work was an evaluation of the influence of those disturbances on hearing organ as potential factors being responsible for perceptive hearing loss in considerable number of the patients with chronic renal failure (CRF). Examination was conducted on 20 children with CRF, aged 10-18 years. In each case, before and after dialysis, on the same day, ENT examination, pure tone audiometry, brain auditory evoked potentials (BAEP) and acoustic otoemissions (TEOAE, DPOAE) were performed. Audiometric tests revealed significantly worse hearing in children with CRF in comparison to healthy subjects with not statistically significant improvement after dialysis. Significantly elongated I, III, V peak latencies as well as I-III and I-V interpeak latencies in BAEP of children with CRF before dialysis were considerable shorter after dialysis except III-V but in 2 of them they appeared after dialysis. In 8 CRF cases DPOAE was present after dialysis in the range of frequencies absent before and in 9 CRF cases there was an increase of the response on the level of 10-15 dB for some frequencies. There were no any changes after dialysis in 3 cases with CRF. The results of our studies reflect subclinical disturbances in neural conduction of auditory pathway and its significant improvement after normalisation of blood parameters (uremic toxins, hyperkalaemia). This fact suggests central component of ureic axonopathy in the pathogenesis of hearing impairment in children with CRF. Dynamism of the changes in TEOAE and DPOAE reflects also the influence of those disturbances on auditory cells on the level of the labyrinth.

Adolescent↗
PubMed2004

Diverse responses of single auditory afferent fibres to electrical stimulation of the inferior colliculus in guinea-pig.

Medial olivocochlear (MOC) neurons in the auditory brainstem project to the cochlea and inhibit cochlear neural output by their action on the cochlear outer hair cells. The function of the lateral olivocochlear (LOC) neurons, projecting to the auditory primary afferents is still under debate. Recent studies have suggested that the olivocochlear system can have frequency-specific, spatially restricted effects within the cochlea. It has been shown that the inferior colliculus (IC) projects to the MOC neurons in a tonotopic manner and that electrical stimulation of the IC can activate the MOC system, suppressing cochlear gross potentials. In addition, it has been shown that stimulation of the IC may be able to activate the LOC neurons. We investigated the effect of IC stimulation on single units in the cochlea of guinea-pigs and searched for evidence of spatially restricted effects of the MOC system and effects of the LOC system. We found a variety of effects on single units. About 40% of units were unchanged whereas others (53%) showed inhibitory effects, reflected in a rightward shift of their rate-level function, sometimes accompanied by a suppression of the spontaneous rate. About 18% of the inhibited neurons showed an increased spontaneous rate. In 5% of the units we observed an excitatory effect of IC stimulation, resulting in a leftward shift of the rate-level functions. We also found that the effect could vary greatly between units of the same and adjacent frequencies within a single animal. These results imply an involvement of another regulatory system besides the MOC system, possibly the LOC system, which acts directly on the primary afferents. These data also demonstrate that the olivocochlear system is capable of eliciting highly localized effects on different frequency regions in the cochlea.

Acoustic Stimulation↗