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At least 1,207 records · Page 67Linked to original sources
PubMed2003

[Use of the auditory brainstem neuroprosthesis in the Czech Republic].

BACKGROUND: Auditory brainstem implant (ABI) is an electroprosthetic device enabling sound sensations in deaf persons with a bilateral lesion of auditory nerves. Stimulation of auditory nuclei in the floor of the IVth ventricle is realized by an electrode array introduced during surgery in the lateral recess of the IVth ventricle. METHODS AND RESULTS: The main indication group for ABI is represented by patients with neurofibromatosis 2 (NF2) suffering from bilateral vestibular schwannomas. During surgery aimed at tumour removal, auditory nerve function and integrity are almost always destroyed, therefore, an ABI can be introduced as an one stage procedure. Implantees use the device mainly as the aid in lipreading, only very rarely they can comprehend speech without visual cues. Auditory brainstem implant programme has been introduced in the Czech Republic in the year 1999. It was the very first ABI surgery in the Central Europe. Since that time, 5 patients had received the auditory brainstem implant, from which the first four use the device for a longer time. CONCLUSIONS: The last operated patient has not been activated yet. It may be said, that ABI represents a benefit to all our patients, in one implanted this benefit is significant, since he can understand speech without lipreading, the other implantees use the device as an aid in lipreading. In one female patient, the device benefit is severely limited by a motoric handicap after partial cerebellar resection during surgery. Nevertheless, she uses the implant on a daily basis, but contact with her is limited and difficult.

Adult↗
PubMed2003

Slow oscillation in non-lemniscal auditory thalamus.

In the present study, we investigated the oscillatory behavior of the auditory thalamic neurons through in vivo intracellular and extracellular recordings in anesthetized guinea pigs. Repeated acoustic stimulus and cortical electrical stimulation were applied to examine their modulatory effects on the thalamic oscillation. The time course of the spike frequency over each trial was obtained by summing all spikes in the onset period and/or the last time period of 100 or 200 msec in the raster display. Spectral analysis was made on the time course of the spike frequency. A slow-frequency oscillation ranging from 0.03 to 0.25 Hz (mean +/- SD, 0.11 +/- 0.05 Hz) was found in the medial geniculate body (MGB) together with a second rhythm of 5-10 Hz. The oscillation neurons had a mean auditory response latency of 17.3 +/- 0.3 msec, which was significantly longer than that of the non-oscillation neurons in lemniscal MGB (9.0 +/- 1.5 msec, p < 0.001, ANOVA) and similar to the non-oscillation neurons in the non-lemniscal MGB (17.6 +/- 5.4 msec, p = 0.811). They were located in the non-lemniscal nuclei of the auditory thalamus. Cortical stimulation altered the thalamic oscillation, leading to termination of the oscillation or to acceleration of the rhythm of the oscillation (the average rhythm changed from 0.07 +/- 0.03 to 0.11 +/- 0.04 Hz, n = 8, p = 0.066, t test). Acoustic stimulation triggered a more regular rhythm in the oscillation neurons. The present results suggest that only the non-lemniscal auditory thalamus is involved in the slow thalamocortical oscillation. The auditory cortex may control the oscillation of the auditory thalamic neurons.

Acoustic Stimulation↗
PubMed2003

Patients with auditory neuropathy/dys-synchrony lack efferent suppression of transient evoked otoacoustic emissions.

Function of the olivocochlear reflex, measured by suppression of transient evoked otoacoustic emissions, is assessed in nine patients with bilateral auditory neuropathy/dys-synchrony and compared to matched control subjects with normal auditory function. TEOAEs were acquired using 65 dB peak sound pressure linear clicks with and without the presence of broad-band noise presented binaurally, ipsilaterally, or contralaterally in a forward masking paradigm. Efferent suppression differed significantly between subject groups (p < .0001). Mean suppression was less than 0.22 dB across all suppressor noise conditions for the auditory neuropathy/dys-synchrony subjects. TEOAE suppression averaged 4.47 (binaural), 2.41 (ipsilateral), and 1.52 (contralateral) dB in the control subjects. Suppression characteristics across the three suppressor conditions were also assessed in one patient with unilateral auditory neuropathy/dys-synchrony. The results suggest that poor efferent responses are related to compromised afferent input to the OCR pathway and support the use of efferent suppression of otoacoustic emissions as a differential measure of auditory function in patients with auditory neuropathy/dys-synchrony.

Acoustic Stimulation↗
PubMedDate not supplied

[Tendencies in auditory physiology].

Main tendencies in studying of human and animals auditory system with psychoacoustical and electrophysiologycal methods are considered. Concerning psychoacoustical studies some basic data are presented as well as contemporary tendencies in hearing physiology in analysis of the intensity, frequency, temporal characteristics of the sound signals and data related to such phenomena as masking and adaptation. Data concerning directional hearing are presented in detail as a basis of auditory virtual reality. In electrophysiological studies of the auditory system detailed analysis of mapping in auditory centers and mechanisms concerning localization of unmoved and moving auditory stimuli was performed. Special attempt was paid to consider the reflection of different types of auditory signals in human evoked potentials.

Animals↗
PubMed1991

Landau-Kleffner syndrome: epileptic activity in the auditory cortex.

The Landau-Kleffner syndrome (LKS) is characterized by electroencephalographic spike discharges and verbal auditory agnosia in previously healthy children. We recorded magnetoencephalographic (MEG) spikes in a patient with LKS, and compared their sources with anatomical information from magnetic resonance imaging. All spikes originated close to the left auditory cortex. The evoked responses were contaminated by spikes in the left auditory area and suppressed in the right--the latter responses recovered when the spikes disappeared. We suggest that unilateral discharges at or near the auditory cortex disrupt auditory discrimination in the affected hemisphere, and lead to suppression of auditory information from the opposite hemisphere, thereby accounting for the two main criteria of LKS.

Aphasia↗
PubMed1990

Improvement of central auditory function after partial temporal lobectomy in a patient with seizure disorder.

This case study reports the auditory findings in one patient with left temporal lobectomy. Behavioral and electrophysiologic central auditory tests were administered just before and 1 week after surgical removal of the left anterior temporal lobe, including the amygdala and portions of the hippocampus. The dichotic digits test and late auditory evoked potentials with P-300 showed marked improvement postoperatively, consistent with improved central auditory function. Postoperative behavioral results on the dichotic digits test are consistent with anatomic evidence that there are few, if any, auditory connections to the anterior temporal lobe. Although electrophysiologic recordings improved postoperatively, they are still considered abnormal. This case study illustrates the use of both behavioral and electrophysiologic procedures for monitoring central auditory function.

Adult↗
PubMed1982

[Electrophysiologic characteristics of representations of the auditory and somatosensory systems in the turtle midbrain].

Experiments with unanesthetized tubocurarine-immobilized turtles show that the auditory representation is localized in the medio-dorsal part of tegmentum, torus semicircularis, which contains monomodal (auditory) and bimodal (auditory and somatosensory) units. The somatosensory system is wider represented, overlapping the auditory system in the medial parts of tegmentum. The focus of auditory representation is localized in lateral parts of the dorsal tegmentum (n. intercollicularis) where monomodal somatic units were recorded. The predominance of contralateral somatic projections is revealed. Frequency-threshold curves based on threshold of evoked potentials were V-shaped but flattened. Range of perceived frequencies was equal to 40-6000 Hz, range of optimal frequencies was 100-400 Hz. Auditory mesencephalic cells may be attributed to three types of discharge patterns: phasic, sustained and burst firing. Tuning to a single optimal frequency was typical of phasic cells but most of cells with sustained firing were sensitive to two or even three frequencies.

Animals↗
PubMed1996

Central tinnitus and lateral inhibition: an auditory brainstem model.

Central tinnitus is used herein either to designate a tinnitus that originates in the central auditory system, or to refer to a component of a peripherally generated tinnitus that is exaggerated by auditory brain mechanisms. Findings from several research areas contribute to this analysis of central tinnitus. The inferior colliculus, in particular, is significant because of the distribution of lateral inhibition in this nucleus and because of the possible change in inhibition that follows bearing loss. There is also a convergence of auditory and non-auditory functions at inferior colliculus. One non-auditory function, the initiation of aversive behavioral responses, may be demonstrated with electrical or chemical stimulation of auditory nuclei in the vicinity of the midbrain. With reduction of central inhibition through hearing loss or aging, tinnitus activity may gain easier access to those subsystems that produce aversive responses. A neural model, conceptually based in inferior colliculus, assumes a pattern of lateral inhibition that is influenced by the distribution of cochlear pathology. Of special importance are the abrupt changes across the tonotopically organized outputs from the cochlea that are reflected in behavioral measures as an 'audiometric edge'. The neural response properties that derive from this assumption are related to properties of central tinnitus.

Acoustic Stimulation↗
PubMed1997

Temporal integration and duration tuning in the dorsal zone of cat auditory cortex.

The present study examined auditory cortical neurons, the responses of which depended on the duration of noise bursts. We recorded from 150 neurons with response latencies exceeding 30 msec and from 28 neurons with OFF responses to auditory stimuli in the dorsal zone of cat auditory cortex. Of 150 long-latency neurons, 132 displayed some form of duration selectivity. Seventy-eight were classified as selective for long durations. Among the long-duration-selective neurons, 30 responded only to noise burst stimuli with durations longer than a minimal threshold and were classified further as duration threshold neurons. Of 132 duration-selective neurons, 41 responded selectively to noise bursts of short duration; 13 showed maximal responses to noise bursts of a particular duration and could be regarded as duration-tuned neurons. OFF-response neurons included ones that were long-duration-selective, duration-tuned, and nonduration-selective. Duration tuning has been described previously only at the midbrain level in amphibians and bats. The present finding of sensitivity to sound duration in at least one region of cat auditory cortex indicates that this form of neural tuning may be important for hearing in all vertebrates, and for processing of sound at multiple levels in the auditory pathway. The duration tuning in the cat auditory cortex was much broader, and the best duration was distributed over a wider range than in the bat inferior colliculus. We suggest that the duration selectivity of the long-latency neurons results from integration along the time domain of a stimulus during the latent period.

Acoustic Stimulation↗
PubMed1997

Protein kinase C in central auditory pathways of the rat.

Protein kinase C is an important intracellular signaling molecule. Many of its ten isoforms are highly expressed in brain, and protein kinase C has been implicated in the regulation of the activity of receptors of several major neurotransmitters, including glutamate, acetylcholine, glycine, and gamma-aminobutyric acid. These neurotransmitters and their receptors are present in central auditory pathways, suggesting their role in auditory signal processing. Although they may be important modulators of the function of these neurotransmitter receptors, the distribution of protein kinase C isoforms in central auditory systems has not been well characterized. By using immunocytochemistry with specific antibodies, we studied the distribution of immunoreactivity of four isoforms of protein kinase C, betaI, betaII, gamma, and gamma, in central auditory systems of rat brain. Each of these protein kinase C isoforms was found to have a unique distribution in the auditory brainstem and cortex, supporting a role for these isoforms of protein kinase C in different aspects of auditory sensory processing.

Animals↗
PubMed1997

Informativeness of the threshold adaptation and fatigue for assessment of the auditory health risk.

The management and control of modern automated productions evidence the elevated role of the auditory system as one of the distant sensor communication systems. The present study informs about the auditory adaptation and fatigue at the end of the working shift of 385 operators at control boards in "Kremikovtzi" State Company. The results of the monitoring of the dynamic changes show significant changes, expressed in aggravation of the auditory fatigue manifestation by moderate to significant disturbance of the adaptation-recovery processes. The analysis established a significant positive correlation between the changes in auditory fatigue and the duration of service. The frequencies of the speech range are preserved for a long time. The elevated auditory fatigue is observed in the injured hearing band 4,000 Hz, followed by 6,000 Hz and continuous dissemination to the middle frequencies of the speech band-2,000 and 1,000 Hz. The results of the study of the adaptation-recovery processes are characterised by statistically significant reliability, single direction and reproducibility and can be applied as informative criteria for assessment of the auditory health risk.

Adult↗
PubMed1997

[Influence of hypoxia on the human auditory system].

The present paper presents a review of the literature on "hypoxia and human auditory mechanisms". It examines and discusses, above all, the results obtained in the various studies using pure tone audiometry and auditory evoked potentials. At the present time, the two areas which appear most sensitive to hypoxia are the cochlea and, above all, the telencephalic auditory cortex (specifically those sectors dedicated to cognitive processing of auditory stimulation). However, many other areas which are sensitive to hypoxia, but to a lesser extent, have also been identified, even in other sectors of the auditory pathway. Particularly worthy of note is the effectiveness of the metabolic compensatory mechanisms which come into play upon hypoxic stress. These mechanisms include vasodilation and the presence of metabolic reservoirs. Nevertheless, there are still a number of open questions regarding how the auditory pathway functions in the case of hypoxia; thus the experimental study of hypoxic hypoxia is still an interesting, fruitful research field in audiology.

Auditory Cortex↗
PubMed1998

Connections among functional areas in the mustached bat auditory cortex.

Connections among functional areas in the mustached bat's auditory cortex were examined by placing anatomical tracers in physiologically defined locations. We identified at least two and probably three channels connecting the various areas. One channel is formed by interconnections among areas containing neurons sensitive to frequency-modulated components (FMs) of the pulse and echo. These neurons are tuned to echo delay, a cue for target range, and thus define a ranging channel. An additional one or two channels are formed by interconnections among areas that contain neurons sensitive to the constant frequency components (CFs) of echoes. These neurons are of two main types: either sensitive to CFs of both pulse and echo (CF/CF neurons) or sensitive to a pulse FM and echo CF (FM-CF neurons). There was only a weak connection between the largest area of each type, suggesting they lie in different channels. Connections among areas in the ranging channel and echo CF-sensitive channel(s) were weak. Thus, the interconnections among functional areas in the mustached bat's auditory cortex define parallel channels for processing different types of biosonar information. Most corticocortical connections were patchy, in a manner suggestive of a columnar organization. The average width of the patches was approximately 360 microm. Based on the sizes of the functional areas, we estimate the auditory cortex contains a total of approximately 150 columns. Individual areas contain from as many as approximately 20 to as few as 1-4 columns. Each area had abundant projections outside of the auditory cortex. Connections within the cortex included the frontal, anterior cingulate, retrosplenial and perirhinal cortices, and the claustrum. Subcortical targets included the amygdyla, auditory thalamus, pons, pretectum, superior and inferior colliculi, and central gray. Projections within the cortex were of modest strength compared with several of the subcortical projections. Thus, the auditory areas themselves are the primary source of cortically processed biosonar information to the rest of the brain.

Animals↗
PubMed1998

Antibody-dependent Fos-like immunoreactivity (FLI) in the auditory pathway of the rat in response to electric stimulation of the cochlea.

The distribution of Fos-like immunoreactivity (FLI) in the auditory pathway was analyzed and quantified in two groups of rats subjected to a similar electric stimulation of the cochlea, but the brains of the two groups were treated with a different antibody against Fos. The brains of control (unstimulated) rats were processed and analyzed in the same way. In a given auditory nucleus, for the same paradigm of stimulation, a very different density of FLI can be found depending on the antibody used to process the tissue. There are auditory nuclei which exhibited a significant activation of FLI as compared to control animals when one antibody was used whereas there was no difference when using the other antibody. In other cases, for both antibodies, a significant FLI increase was observed in relation to the stimulus. However, the increase of FLI density was significantly greater in some auditory nuclei with one antibody, while it was the reverse in other auditory nuclei. The present data demonstrate quantitatively that the use of two different Fos antibodies can strongly affect the FLI produced in the auditory pathway by electric stimulation of the cochlea, confirming previous qualitative observations based on acoustic stimulation of the cochlea.

Animals↗
PubMedDate not supplied

[The cerebral control of the somatosensory and auditory afferent projections to the cerebral cortex in man and animals].

The main purpose of the present paper was consisted in studying of topology (spreading) of the somatosensory and auditory projections in cortex of both brain hemispheres in humans under different functional states conditions: during quiet walking state and during realization of the meditative programme. At the same time for the purpose of verification these steering mechanisms a number of experiments were realized in animals with neurosurgical cutting of brainstem ascending projections, which control the transfer of somatosensory and auditory sensibility. Experimental study was realized with two groups of subjects--8 subjects (age from 25 to 35 years old) and 25 (age from 25 to 40 years old) subjects practicing technique of Transcendental Meditation (TM). In addition to the mentioned above group some groups of animals were used in the experiments. Among them there were used the groups of monkeys (8 macaque rhesus and macaque nemestrina) and cats (10 animals) in conditions of acute experiment, under tiopenthal anesthesia. Two experimental methods were used in the study: electrophysiological for subjects and neurosurgical, additionally for animals. For evaluation of the brain reactivity in subjects registration of the somatosensory, to median nerve stimulation, and auditory, to bilateral application of auditory clicks, evoked potentials (EPs) in the symmetrical cortical structures of the brain was used. Registration of the somatosensory and auditory evoked potentials in animals was realized not only from the cortex, but from the brainstem somatosensory and auditory structures. SSEP in subjects-meditators were registered before and during meditation programme. In animals SSEP and AEP registration on the corresponding stimuli realized before and after neurosurgical operation--section of the midbrain tegmentum. Specific alterations of the early (up to 80 ms) and late components SSEP and AEP complexes in forms of topology spreading and diminution of registration areas of these components were obtained during the meditation. Origins of these functional reorganization are discussed from the positions of internal 'feed-back' inhibition.

Adult↗
PubMed1998

Signals from the superficial layers of the superior colliculus enable the development of the auditory space map in the deeper layers.

We have examined whether the superficial layers of the superior colliculus (SC) provide the source of visual signals that guide the development of the auditory space map in the deeper layers. Anatomical tracing experiments with fluorescent microspheres revealed that a retinotopic map is present in the newborn ferret SC. Aspiration of the caudal region of the superficial layers of the right SC on postnatal day 0 did not cause a reorganization of this projection. Consequently, recordings made when the animals were mature showed that visual units in the remaining superficial layers in rostral SC had receptive fields that spanned a restricted region of anterior space. Auditory units recorded beneath the remaining superficial layers were tuned to corresponding anterior locations. Both the superficial layer visual map and the deeper layer auditory map were normal in the left, unoperated SC. The majority of auditory units recorded throughout the deeper layers ventral to the superficial layer lesion were also tuned to single sound directions. In this region of the SC, however, we observed much greater scatter in the distribution of preferred sound directions and a significant increase in the proportion of units with spatially ambiguous responses. The auditory representation was degraded, although many of these units were also visually responsive. Equivalent lesions of the superficial layers made in adult ferrets did not alter the topographic order in the auditory representation, suggesting that visual activity in these layers may be involved in aligning the different sensory maps in the developing SC.

Age Factors↗
PubMed1998

Auditory connections and neurochemistry of the sagulum.

We studied the cytoarchitecture, neurochemical organization, and connections of the sagulum. The goal was to clarify its role in midbrain, lateral tegmental, and thalamic auditory processing. On cytoarchitectonic grounds, ventrolateral (parvocellular) and dorsomedial (magnocellular) subdivisions were recognized. The patterns of immunostaining for gamma-aminobutyric acid (GABA) and glycine were distinct. Approximately 5-10% of the neurons were GABAergic, and more than one type was identified; GABAergic axon terminals were abundant in number and varied in form. Glycinergic neurons were much rarer, < 1% of the population, and glycinergic axon terminals were correspondingly sparse. Wheat germ agglutinin conjugated to horseradish peroxidase was used for purposes of connectional mapping, and biotinylated dextran amines revealed the structure of corticosagular axons. All nine cortical areas injected project to the ipsilateral sagulum. Five (areas AI, AII, SF, EPD, and Te) had heavier projections than the others. Areas AI and AII projected throughout the rostrocaudal sagulum. Labeling from AI was moderate in density and concentrated in the central sagulum, whereas the input from AII was heavier and ended more laterally. Suprasylvian fringe input was light, especially caudally, and was chiefly in the central sagulum. The projection from the dorsal region of the posterior ectosylvian gyrus was comparatively stronger and was in the dorsolateral sagulum. Finally, the temporal cortex sent axons to the most lateral sagulum, spanning the dorsoventral extent, whereas insular cortex axons ended diffusely in the dorsolateral sagulum. Corticofugal axons ranged from fine boutons en passant to larger globular terminals. The sagulum may represent the earliest significant opportunity in the ascending auditory pathway for corticofugal modulation. The most extensive input arises from the polymodal association areas. The sagulum then projects divergently to the dorsal cortex of the inferior colliculus and the dorsal division of the medial geniculate body. The projection from the dorsal division of the auditory thalamus to nonprimary auditory cortex completes this circuit between the forebrain and the midbrain and represents a nexus in the ascending and descending auditory systems. Such circuits could play a critical role in auditory-motor adjustments to sound.

Anatomy, Artistic↗
PubMed1996

Auditory evoked potentials in multiple sclerosis: correlation with magnetic resonance imaging.

The present study addresses issues regarding the location of neural sources (i.e. generators) of human auditory evoked potentials (AEPs), and the pattern of neural conduction in the auditory pathway. AEPs were recorded from fifteen patients with multiple sclerosis (MS) and compared to normals. The recordings included auditory brainstem responses (ABRs), mid-latency responses (MLRs), and long-latency responses (LLRs). AEP latency abnormalities were related to the locus of demyelinating lesions, as determined by magnetic resonance imaging (MRI) scans. The data demonstrated several anatomical patterns relating abnormal ABR wave intervals and abnormal MRI signals. From these patterns specific loci for ABR neural sources in the brainstem might be postulated. In addition, the earlier the ABR waves, the more unilateral the abnormalities appeared, suggesting bilateral sources for later waves. The MLRs were highly correlated with ABR wave V and were associated with greater abnormality in MRI signals in midbrain and forebrain regions. In general, patients with abnormal LLRs also had widespread AEP and MRI abnormalities, supporting a multiple source approach for the N1 wave of the LLRs. The observation that LLRs were only abnormal in the presence of bilateral ABR abnormalities suggests a cross wiring which would serve as a compensatory mechanism for unilateral disturbances. The AEP data showed dissociation between early and late wave abnormalities, thus supporting parallel channels for neural conduction in the central auditory system. Such a model calls for some degree of independence of AEP generators along the auditory pathway.

Adult↗