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At least 991 records · Page 55Linked to original sources
PubMed1992

Kainic acid lesions of the dorsal nucleus of the lateral lemniscus: effects on binaural evoked responses in rat auditory cortex.

The effects of unilateral lesions of the dorsal nucleus of the lateral lemniscus (DNLL) on binaural processing were examined by measuring the amplitude of auditory cortical evoked responses in the albino rat. Lesions were made by pressure injection of small quantities of kainic acid through a micropipette lowered into the lateral lemniscus. Comparisons were made between normal animals and animals with unilateral DNLL damage. In normal animals, the amplitude of evoked potentials recorded from left and right primary auditory cortex varied as a function of the time difference between clicks delivered to the two ears. Maximum responses were obtained from the hemisphere contralateral to the leading click, and response amplitude was progressively reduced as the interaural time difference (ITD) was shifted in favor of the ipsilateral ear over the range from +600 microseconds to -600 microseconds. The functions in the left and right hemisphere were symmetrical mirror images of one another. Destruction of the DNLL had no significant effect on the maximum response amplitude, evoked response threshold, or response latency in either hemisphere. On the other hand, the lesion did have the effect of greatly reducing the slope of the ITD function in the hemisphere contralateral to the lesion. The change in slope was attributed to a reduction in the strength of inhibition produced by stimulation of the ipsilateral ear. No effect was seen on the slope of the function in the ipsilateral hemisphere. Animals with lesions that spared DNLL but destroyed the intermediate and ventral nucleus of the lateral lemniscus had normal binaural response functions. These data show that the DNLL plays an important role in shaping binaural responses in the contralateral auditory pathway.

Animals↗
PubMed1995

Nucleus 20-channel and 21-channel auditory brain stem implants: first European experiences.

Central electrical stimulation of the auditory pathway can allow hearing in patients suffering from deafness localized in the auditory nerve. Developments in a multichannel auditory brain stem implant based on the Nucleus Mini 22 cochlear implant with transcutaneous signal transmission is discussed. The device has been implanted in seven European patients who suffered from neurofibromatosis type 2. Preliminary speech perception results and patient satisfaction are encouraging, and the data presented include some limited open-set speech recognition.

Auditory Threshold↗
PubMed1997

Central auditory evaluation of patients with spasmodic dysphonia.

Spasmodic dysphonia is a focal laryngeal dystonia characterized by inappropriate contractions of the intrinsic laryngeal musculature. The prevalence of associated neurological findings has led to detailed investigation of the central nervous system. Previous research revealed latency abnormalities in patients' auditory brainstem responses. The present study further investigated central auditory findings in patients with spasmodic dysphonia, including brainstem and cortical function. Fourteen normal-hearing patients with spasmodic dysphonia were tested using the auditory brainstem response (ABR) and SCAN-A test of central auditory processing. The ABR estimated brainstem transmission time and evaluated auditory pathway integrity at a high stimulus rate. SCAN-A assessed the auditory cerebral cortex. Implications of these findings are discussed. We found no ABR abnormalities in subjects with spasmodic dysphonia. Positive SCAN-A findings were negligible. The ABR findings contradict previous reports.

Adult↗
PubMed1998

The effects of qi-gong and acupuncture on human cerebral evoked potentials and electroencephalogram.

Although a number of studies on traditional Chinese medicine, such as qi-gong (QG), acupuncture (AC), moxibustion and Chinese herbal drugs, have been reported in recent years, there are few reports on human cerebral evoked potentials (EPs), especially relating only to QG and AC. In the present study, we examined the changes in EPs and electroencephalogram (EEG) by QG, and by AC stimulation to the point called "Zusanli" on the left lower leg, with one healthy male adult. 1. With regard to the effect of QG, significant changes in EP-components originated from the cortex suggest both facilitating and inhibitory effects of QG on the cortex. However, no significant changes in EP-components originated from the subcortex and no significant changes in EEG power% suggest that QG does not affect the subcortex. 2. With regard to the effects of AC, significant changes in EP-components originated from the cortex suggest facilitating and inhibitory effects of AC stimulation on the cortex. Furthermore, it is suggested that AC stimulation has few effects on the somatosensory and the visual pathways up to the cortex, while it has complicated effects on the auditory pathway up to the cortex.

Acupuncture Therapy↗
PubMed1992

Sensory and movement-related cortical potentials in nociceptive and auditory reaction time tasks.

The processing of a sensory stimulus leading to a simple motor command was studied with scalp-recorded long latency cortical potentials in humans. Two sensory modalities were tested in their ability to activate descending motor pathways: auditory stimuli and painful cutaneous stimuli produced by a CO2 laser. Subjects were asked to react to stimuli with voluntary index finger movements. The stimulus-related and movement-related cortical potentials were recorded simultaneously with five midline electrodes on the scalp. The auditory reaction time, measured from the stimulus to the onset of electromyogram (EMG), was faster (150 ms) than the laser reaction time (350 ms). The onset of EMG of finger movements occurred only after the first negative components following auditory or laser stimuli but before the positive components. The latency from the auditory negativity to the onset of EMG was about 50 ms and the latency from the laser negativity to the onset of EMG was about 110 ms. This finding indicates that not only the peripheral afferent conduction but also central processing takes longer in a pain-related somatosensory task than in an auditory task. The frontal peak of Motor Potential (fpMP), a cortical potential related to the sensory feedback from movement, occurred with a constant latency after the onset of EMG (100 ms) and was unaffected by the task.

Adult↗
PubMed2000

Linear and nonlinear pathways of spectral information transmission in the cochlear nucleus.

At the level of the cochlear nucleus (CN), the auditory pathway divides into several parallel circuits, each of which provides a different representation of the acoustic signal. Here, the representation of the power spectrum of an acoustic signal is analyzed for two CN principal cells-chopper neurons of the ventral CN and type IV neurons of the dorsal CN. The analysis is based on a weighting function model that relates the discharge rate of a neuron to first- and second-order transformations of the power spectrum. In chopper neurons, the transformation of spectral level into rate is a linear (i.e., first-order) or nearly linear function. This transformation is a predominantly excitatory process involving multiple frequency components, centered in a narrow frequency range about best frequency, that usually are processed independently of each other. In contrast, type IV neurons encode spectral information linearly only near threshold. At higher stimulus levels, these neurons are strongly inhibited by spectral notches, a behavior that cannot be explained by level transformations of first- or second-order. Type IV weighting functions reveal complex excitatory and inhibitory interactions that involve frequency components spanning a wider range than that seen in choppers. These findings suggest that chopper and type IV neurons form parallel pathways of spectral information transmission that are governed by two different mechanisms. Although choppers use a predominantly linear mechanism to transmit tonotopic representations of spectra, type IV neurons use highly nonlinear processes to signal the presence of wide-band spectral features.

Acoustic Stimulation↗
PubMed1994

Moderate hypoglycemia impairs the function of the inferior colliculus in the awake rat.

To assess the effect of acute hypoglycemia on the brain stem auditory pathway, we implanted electrodes into the inferior colliculus (IC) and subsequently recorded auditory-evoked potentials from the IC (ICEP) and brain stem (BAEP) in normal awake rats during euglycemic and hypoglycemic hyperinsulinemia (2 hours). Latencies of the ICEP and peak V of the BAEP were significantly prolonged by hypoglycemia (approximately 2.7 mmol/L). The change in the BAEP was principally between peak III and peak V. suggesting an effect in or near the IC. ICEP and BAEP latencies did not change during euglycemic hyperinsulinemia. We conclude that the function of the IC is very sensitive to episodes of moderate hypoglycemia. These data provide direct evidence that the scope of adverse central nervous system effects resulting from hypoglycemia extends beyond cognitive centers to include the brain stem.

Acute Disease↗
PubMed2001

Transferring an inborn auditory perceptual predisposition with interspecies brain transplants.

Inborn species' perceptual preferences are thought to serve as important guides for neonatal learning in most species of higher vertebrates. Although much work has been carried out on experiential contributions to the expression of such preferences, their neural and developmental correlates remain largely unexplored. Here we use embryonic neural transplants between two bird species, the Japanese quail and the domestic chicken, to demonstrate that an inborn auditory perceptual predisposition is transferable between species. The transfer of the perceptual preference was dissociated from changes to the vocalizations of the resulting animals (called chimeras), suggesting that experiential differences in auditory self-stimulation cannot explain the perceptual change. A preliminary localization of the effective brain region for the behavioral transfer by using a naturally occurring species-cell marker revealed that it is not contained within the major avian auditory pathways. To our knowledge, this is the first demonstration that abstract aspects of auditory perception can be transferred between species with transplants of the central nervous system.

Animal Communication↗
PubMed1988

Modification of neuromagnetic responses of the human auditory cortex by masking sounds.

We have studied the effects of masking sounds on auditory evoked magnetic fields (AEFs) of healthy humans. The AEFs were elicited by 25-ms tones presented randomly to the left or to the right ear, and the responses were recorded over the right auditory cortex. Without masking, the 100-ms deflection (N100m) was of somewhat higher amplitude and of shorter latency for contra- than ipsilateral stimuli. Continuous speech, music, or intermittent noise, delivered to the left ear, dampened N100m to stimulation of both ears without correlated changes in sensation. Intermittent noise had a weaker effect on N100m than speech or music. Continuous noise fed to the left ear dampened both the sensation of and the responses to the left-ear stimuli, with no significant effect on the responses to the right-ear stimuli. The results suggest that the masking effects of continuous noise, seen at the auditory cortex, derive mainly from the periphery whereas the effects of sounds with intensity and frequency modulations take place at more central auditory pathways.

Acoustic Stimulation↗
PubMed1985

A deoxyglucose study on auditory responses in the bat Rhinolophus rouxi.

Responses in the auditory system of the echolocating bat Rhinolophus rouxi were mapped with [3H]deoxyglucose (DG) autoradiography. After unilateral stimulation with the constant frequency component of the individual bat's echolocation call, stimulus-related DG uptake occurred contralaterally in the dorsolateral and the ventromedial parts of the inferior colliculus, in the ventral medial geniculate body and in the contralateral neocortex. Unilateral 50 kHz-stimulation gave rise to a weakly activated lamina in the dorsolateral contralateral inferior colliculus. The distribution of frequency-evoked DG uptake within the inferior colliculus agrees with electrophysiological findings on an acoustic fovea in the auditory pathway of echolocating bats.

Acoustic Stimulation↗
PubMed1984

Simultaneous recording of auditory evoked potentials. Relationships among the fast, middle and long latency components.

The whole pattern of the fast, middle and long latency auditory evoked potentials (AEP) was recorded simultaneously from the scalp surface of 13 normal-hearing adults. The individual responses were displayed on a nonlinear time axis in order to improve identification of the components. Stimulation consisted of 2048 unfiltered clicks, delivered monaurally at 80, 60, 40 dB HL with an ISI of 750 ms. Changes in mean latency and amplitude of each AEP component were statistically evaluated in relation to intensity and electrode montage (vertex-mastoid ipsi- and contralateral to the stimulated ear). The latencies of fast components I-VI and the slow P1 increase significantly with declining stimulus intensity. The amplitudes of the fast, I, II, III, V and the slow P1-N1, P2-N2 decrease significantly with intensity. As regards differences due to the electrode montage the contralateral recording causes significant changes in latency of the fast potentials up to wave IV, and changes in amplitude of the fast up to wave V, and of the slow P1-N1 and P2-N2. Therefore, as their latency and amplitude seem to be less closely related to the stimulus and electrode placement, the middle components behave differently, compared with the preceding and following components. Based on parametric comparisons of potentials ranging widely in latency, but each one evoked by an equal sensory input, this kind of AEP evaluation may be useful both for neurophysiological and clinical studies of the whole auditory pathway function.

Adult↗
PubMed1994

Effects of olivocochlear bundle section on otoacoustic emissions in humans: efferent effects in comparison with control subjects.

The effects of contralateral acoustic stimulation on evoked otoacoustic emissions (OAE) were examined in three subject groups in order that the impact of efferent olivocochlear bundle section (as a consequence of vestibular neurectomy) could be compared with normal findings, and with a control surgical population. Results demonstrated that the inhibitory effect of contralateral noise on OAE amplitude was absent from the cochlea with severed efferent fibers. These findings appear to be independent of acoustic reflex activity, as suppression was absent despite normal reflexes. Inter-aural suppression of emissions recorded from the patients' intact cochleae act as a control and show a clear reduction in amplitude during contralateral stimulation in a frequency specific pattern consistent with normal findings. Patients who had undergone a similar surgical approach for vascular decompression of the VIIIth nerve without vestibular nerve section, were studied in order to assess the impact of retrolabyrinthine surgery on inter-aural suppression. Inhibition of OAE amplitude was maintained in all control cases in both the operated and intact sides, and was consistent with suppression observed in normal subjects, suggesting that the surgical procedures had not disturbed inter-aural suppression of otoacoustic emissions. It is concluded that the olivocochlear efferent system, when activated by low level contralateral acoustic stimulation, has an inhibitory role in controlling the cellular mechanisms responsible for the generation of otoacoustic emissions in humans. OAE techniques in conjunction with contralateral acoustic stimulation may thus prove to be of value in providing a rapid and non-invasive clinical test of efferent function and offer a means of investigating the functional significance of the efferent auditory system in humans.

Acoustic Stimulation↗
PubMed1984

Auditory brain-stem evoked potentials in Bell's palsy.

In an attempt to assess objectively the integrity of the auditory pathways in patients suffering from Bell's palsy, an audiometric evaluation was performed and auditory brain-stem evoked potentials (ABEP) were obtained from 24 patients within the first week from the onset of facial weakness. Despite negative audiometric findings, significant ABEP abnormalities (greater than 2.5 SDs) were observed for 25% of the sample. In each case the ABEP deviation suggested prolonged brain-stem conduction time; for some patients the aberration was only apparent with an increased stimulus repetition rate. The ABEP measures were found to be independent of the side or severity of the paralysis, the acoustic reflex, or reported dysacusis. The ABEP was of no value in predicting recovery of facial muscle function. It is suggested that the facial paralysis may be only the overt manifestation of a generalized pathologic condition.

Acoustic Impedance Tests↗
PubMedDate not supplied

Electrical response audiometry (ERA) in infants.

The electric response audiometry is a useful diagnostic technique for identifying hearing loss in infants. Among the various electrical responses, the BSER enables us to arrive at an accurate early clinical diagnosis of hearing loss in infants so that effective auditory input, which is the prime requisite for the conceptual foundation for the growth of communication, can be provided through appropriate intervention programmes. The electric response audiometry provides information regarding the physiologic state of the peripheral organs and auditory pathways but however, cannot ascertain whether the infant can hear, in terms of perceiving auditory information. Inspite of this major limitation, the growing acceptance of brainstem electrical potentials in clinics and laboratories throughout the world attests to their increasing importance especially in the assessment of hearing sensitivity of infants.

Audiometry, Evoked Response↗
PubMed2002

An auditory brainstem implant system.

Neurofibromastosis type II (NF2) is a condition that may result in bilateral acoustic neuromas. The tumors and their removal may cause profound bilateral deafness. Because the auditory nerve is compromised, people with NF2 are unable to receive a cochlear implant to restore a sensation of hearing. Electrical stimulation of the auditory pathway can provide hearing in such people. This is possible by means of an auditory brainstem implant (ABI). This article focuses on the MED-EL high-rate multichannel ABI system. The system consists of the implanted and external components. Appropriate placement of the ABI is dependent on electrical auditory brainstem response testing performed intra-operatively. Data on a group of European patients implanted with the MED-EL ABI are presented. Results are promising and include some open-set speech ability.

Acoustic Stimulation↗
PubMed2005

Structural brain changes in tinnitus.

Tinnitus is a common but poorly understood disorder characterized by ringing or buzzing in the ear. Central mechanisms must play a crucial role in generating this auditory phantom sensation as it persists in most cases after severing the auditory nerve. One hypothesis states that tinnitus is caused by a reorganization of tonotopic maps in the auditory cortex, which leads to an overrepresentation of tinnitus frequencies. Moreover, the participation of the limbic system in generating tinnitus has been postulated. Here we aimed at identifying brain areas that display structural change in tinnitus. We compared tinnitus sufferers with healthy controls by using high-resolution magnetic resonance imaging and voxel-based morphometry. Within the auditory pathways, we found gray-matter increases only at the thalamic level. Outside the auditory system, gray-matter decrease was found in the subcallosal region including the nucleus accumbens. Our results suggest that reciprocal involvement of both sensory and emotional areas are essential in the generation of tinnitus.

Adult↗
PubMed1996

Sensorineural hearing deficit: a systematic approach based on imaging findings.

Sensorineural hearing loss (SNHL) can be classified audiometrically into two varieties: sensory (cochlear) and neural (retrocochlear). Individuals with sensory SNHL have damage to the "end organ" (the cochlea) at a macroscopic or microscopic level. When present, imaging manifestations may involve the bony labyrinth or membranous labyrinth. Abnormalities of the bony labyrinth are demonstrable primarily with computed tomography and include demineralization, congenital deformities, traumatic lesions, and erosive or destructive lesions. Abnormalities of the membranous labyrinth include enhancement and hemorrhage, which are demonstrable with magnetic resonance (MR) imaging, and obliteration, which may be diagnosed with either modality. Individuals with neural (retrocochlear) SNHL have involvement of the remainder of the auditory pathway exclusive of the cochlea. This type of SNHL requires study of the internal auditory canal, cerebellopontine angle, brain stem, thalamus, and temporal lobe. The entirety of this type of examination is best performed with high-resolution MR imaging in virtually all cases.

Cochlear Diseases↗
PubMed2003

Auditory evoked responses in postmenopausal women on hormone replacement therapy.

The effect of hormone replacement therapy (HRT) was studied in 32 postmenopausal women on their auditory Evoked Potentials i.e. auditory brainstem response (ABR), Middle latency response (MLR) & slow vertex response (SVR). Recordings were done on computerized evoked potential recorder using 10/20 system of electrode placement and standard click stimuli. A significant improvement in neural transmission was observed as was evidenced by decrease in the ABR wave latencies I, III, IV & V and interpeak latency III-V and I-V after 6 months of HRT. A similar significant decrease was observed in MLR wave latencies of Po, Na & Pa. The SVR wave latencies although found to be decreased after HRT, could not reach the level of statistical significance. There was a significant inverse correlation obtained between latencies of wave I in ABR, Po in MLR and serum estradiol. The results indicate the effect of sex hormone in improving transmission in auditory pathway from periphery through brainstem, thalamus upto cortex. However slow vertex responses indicate that auditory association areas are not much affected. This might have bearing on improvement of neuropsychological functions in postmenopausal women on HRT.

Acoustic Stimulation↗