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Electromagnetic stimulation of the auditory system of deaf patients.

Electromagnetically induced auditory perception was investigated in 18 deaf patients who were candidates for cochlear implants. In the extracranial magnetic stimulation (EMS) procedure, patients were stimulated with time-varying magnetic field brief pulses from a coil positioned at the i) auricle, ii) the mastoid, and iii) the temporal lobe area. EMS elicited auditory sensations in 26 ears (of 14 patients/subjects). The lowest threshold of auditory sensation (TAS) was found to be at the 20% EMS level, with a range of 20-50% of the maximum level (2.0 Tesla), and approximately equal sensitivity in each coil position. Eleven of the subjects hearing EMS-induced sound perceived changes in pitch while 6 heard "clicks" or clicks and tones. Spearman Rho correlation analysis showed a mild negative correlation between the EMS/TAS and the pre-implant FFA, best tone threshold (BTT), and direct promontorial electrical stimulation (ES) thresholds at 250 Hz and 500 Hz. No correlation was found between EMS or ES and performance on the pre-implant or post-implant psychacoustic tests (MAC VIII or 3-Digit speech tests) or the measurements of the thickness of cutaneous and osseous tissue from the stimulation sites at the mastoid and ear canal to the cochlear and 8th nerve. A fair positive correlation was found between the EMS/TAS and the post-implant (6 months) ES threshold when the electrodes allocated the 500 Hz frequency range were stimulated. A mild positive correlation between the pre-cochlear-implant promontorial electrical stimulation (ES) at 250 Hz and the four frequency tone average (FFA: 0.5, 1, 2, 4 kHz) was also found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

A case of cortical deafness and anarthria.

Generally, cortical deafness is not complicated by anarthria and cortical anarthria does not affect auditory perception. We report a case of simultaneous progressive cortical deafness and anarthria. At the age of 70 years, the patient, a woman, noticed hearing problems when using the telephone, which worsened rapidly over the next 2 years. She was then referred to our hospital for further examinations of her hearing problems. Auditory tests revealed threshold elevation in the low and middle frequencies on pure-tone audiometry, a maximum speech discrimination of 25% and normal otoacoustic emissions and auditory brainstem, middle- and long-latency responses. An articulation test revealed abnormal pronunciation. Because of these problems only written and not verbal communication was possible; her ability to read and write was unimpaired. She showed no other neurological problems. Brain MRI demonstrated atrophic changes of the auditory cortex and Wernicke's language center and PET suggested low uptake of (18F) 2-fluoro-2-deoxy-d-glucose around the Sylvian fissures in both hemispheres. Neurologically, the patient was suspected of having progressive aphasia or frontotemporal dementia. Her cortical deafness and anarthria are believed to be early signs of this entity.

Aged↗

Double posterior labyrinthotomy technique: results in three Med-El patients with common cavity.

HYPOTHESIS: This study reports on the use of the double posterior labyrinthotomy surgical technique and a custom-designed electrode to ensure better positioning of stimulating electrodes within the common cavity and thus demonstrate suitable outcomes in patients. BACKGROUND: Cochlear implantation has proven beneficial for numerous children with congenital malformations of the inner ear. Several studies show good auditory perception outcomes in children with common cavity. However, there have been risks involved with surgical techniques used in the actual implantation. These include possible aberrant facial nerve and the strong potential for a cerebrospinal fluid gusher. Improved surgical techniques and electrode design could allow for better electrode contact and avoid electrode placement in the internal auditory meatus. METHOD: The double posterior labyrinthotomy technique was carried out in three cases using a custom made MED-EL COMBI 40+ electrode. RESULTS: Surgery was carried out with no complications and is no more technically demanding than other standard surgical approaches. The speech processor program remains stable over time, and auditory perception results are similar to those obtained from children with no cochlear abnormalities. CONCLUSION: These results demonstrate the success of the double posterior labyrinthotomy approach with modified cochlear implant, and this could be recommended as the procedure of choice in children presenting to an implant team with a common cavity.

Child, Preschool↗

Some aspects of auditory space, speech perception and the use of hearing aids.

The auditory space of an individual is operationally defined as that perceptual area that lies between the upper tolerance level for loud sounds and the threshold of hearing for a specified range of frequencies. Results from recent experimental work are presented to show a difference of some 15 dB between comfortable listening level and loudness discomfort-level, up to 80 dB hearing loss. Results are also shown for the measurement of reaction time to a 2AFC task testing the ability to discriminate initial consonants. Loudness scaling is suggested as a method of eliciting supra-threshold measurements which might be helpful in the fitting of hearing aids.

Audiometry, Speech↗

Human auditory system response to pulsed radiofrequency energy in RF coils for magnetic resonance at 2.4 to 170 MHz.

The threshold conditions for an auditory perception of pulsed radiofrequency (RF) energy absorption in the human head have been studied on six volunteers with RF coils for magnetic resonance (MR) imaging. For homogeneous RF exposure with MR head coils in the 2.4- to 170-MHz range and pulse widths 3 microseconds less than or equal to Tp less than 100 microseconds, the auditory thresholds were observed at 16 +/- 4 mJ pulse energy. Localized RF exposure with optimized surface coils positioned flush with the ear lowers the auditory threshold to only 3 +/- 0.6 mJ. The hearing threshold of RF pulses with Tp greater than 200 microseconds occurs at more or less constant peak power levels of typically 150 +/- 50 W for head coils and as low as 20 W for surface coils. The results from this study confirm theoretical predictions from a thermoelastic expansion model and compare well with reported thresholds from near field antenna measurements at 425 to 3000 MHz. Details of the threshold dependence on RF pulse length reveal primary sites of RF to acoustic energy conversion at the mastoid and temporal bone region and the outer layer of the brain from where thermoelastically generated pressure transients excite audible pressure waves at the resonance modes of the skull around 1.7 kHz and of the brain around 11 kHz. If not masked by usually dominating noise from switched gradients, the conditions for hearing RF pulses, as applied to head coils in MR studies with flip angle alpha at main field B0, is given by Tp/ms less than or equal to 0.4 (alpha/pi)B0/[T]. At peak power levels up to 15 kW presently available in clinical MR systems, there is no evidence known for detrimental health effects arising from the RF auditory phenomenon which is a secondary cause associated with primary RF to thermal energy conversion in body tissues. To avoid the RF-evoked sound pressure levels in the head rising above the discomfort threshold at 110 dB SPL, an upper limit of 30 kW applied peak pulse power is suggested for head coils and 6 kW for surface coils.

Auditory Perception↗

[Diagnosis of central hearing disorders in childhood].

As a contribution to the diagnosis of central auditory disorders in children we developed a series of tests providing a basis for the analysis of auditory perception dysfunctions, offering a detailed description of their symptomatology and thus furnishing a basis for carefully directed measures of treatment. Evaluation criteria necessary for the analysis of tests featuring artificially altered language (band-pass-filtered speech, time-compressed speech, tests with background noise or dichotic speech) are described together with findings obtained from previous investigations. The test series further includes objective audiometric methods and additional tests for the evaluation of auditory perception performance (e.g. phoneme discrimination).

Audiometry↗

Gender-specific hemispheric asymmetry in auditory space perception.

This study aimed to investigate gender-related functional asymmetries in monaural sound localization in the vertical plane. In a simple pointing task, right-handed subjects localized vertical positions of sound sources using only one ear. Results show that females were more precise when listening with the left ear, while males did better with the right. However, significant differences in monaural localization performance as a function of gender occurred exclusively when listening with the right ear, with males performing substantially more precisely than females. These findings suggest gender-related differences in the intrahemispheric functional organization of the left hemisphere for the processing of monaural spatial cues. It is proposed that the results may be related to the sexual dimorphism of the posterior parietal cortex, or planum temporale, both areas known to be involved in spatial auditory functions.

Acoustic Stimulation↗

[Cochlear implantation in visually impaired patients--long-term rehabilitation results].

UNLABELLED: The aim of the study was to assess the rehabilitation results in visually impaired patients with cochlear implants. Material consisted of 9 patients (2 with prelingual deafness, 3 with perilingual deafness, 4 with postlingual deafness) from 244 implanted persons in Poznań. METHODS: In all the patients the rehabilitation results were evaluated using Test of Auditory Perception of Speech (TAPS) and screening test. RESULTS: In the group of patients with pre- and perilingual deafness a little bit slower progress of rehabilitation was found, according to 117 persons with prelingual deafness and 34 persons with perilingual deafness without vision disorders. Within the group of patients with postlingual deafness important progress of rehabilitation was observed. Two brothers with Usher syndrome 1-2 months after speech processor switch-on reached the highest level of test, they could communicate with family. One person after 5 months of rehabilitation could talk by phone without any problems. In all implanted visually impaired patients improvement of auditory perception of speech was observed.

Adolescent↗

Psychoacoustic and electrophysiologic correlates of central hearing disorders in man.

Evaluation of central hearing disorders in neuropsychologic patients is handicapped by their insufficient ability to describe auditory deficits and by the lack of easily applicable audiological tests. A novel psychoacoustic discrimination test (PDT) was developed to determine ear asymmetries in the discrimination of changes in intensity, frequency, or temporal structure of regularly presented dichotic stimuli. In 19 of 21 patients with lesions of the auditory cortex or the acoustic radiation according to CT scan evaluation a higher error score was observed for target stimuli presented at the ear contralateral to the side of brain infarction (6 right, 15 left). In the remaining 2 and in 3 other patients with lesions sparing auditory structures no significant ear asymmetries were seen. This may indicate that auditory perception is reduced in patients with only one intact auditory cortex or one intact acoustic radiation, possibly because of a limitation in information processing capacity. Auditory evoked potential results are presented for a normal subject and two patients to illustrate electrophysiologic correlates of central hearing disorders. Using a transformation of scalp into dipole source activity (Scherg and von Cramon 1986), a unilateral loss of middle latency activity was found in case A, who had a lesion of the left acoustic radiation. The extended lesion of the right auditory cortex in case B resulted in a loss of both middle and late latency dipole source potentials of the right temporal lobe. In both cases a corresponding increase in the PDT error score on the contralateral ear was found.

Adult↗

Vestibular fold flap for post-cordectomy laryngeal reconstruction.

OBJECTIVES: The development of techniques causing fewer sequelae without compromising oncologic control has led to better phonation, breathing, and postoperative swallowing in patients submitted to cordectomy. The objective of the present study was to describe post-cordectomy laryngeal reconstruction with a vestibular fold flap and to analyze the resulting laryngeal functions. STUDY DESIGN: Prospective study. METHODS: Ten patients, 9 males and 1 female, aged 45 to 75 years (mean, 64.5 years), were evaluated. The patients had squamous cell carcinomas in the glottic region and were treated surgically by laryngofissure and cordectomy with the use of a vestibular fold flap for laryngeal reconstruction. The patients were followed up for functional laryngeal analysis that consisted of videolaryngostroboscopy, endoscopic evaluation of swallowing, and voice recording for perceptive auditory analysis, and for computing purposes. RESULTS: No patients depended on tracheostomy during the late postoperative period. No stenosis, anterior synechia, granuloma, or laryngocele were detected, although 1 patient developed immobility in the median position of the operated hemilarynx, which, however, was not sufficient to impair the respiratory function. No alterations in the pharyngeal phase of swallowing were observed by endoscopic evaluation. Using the GRBAS scale, we observed moderate (30%) and severe (20%) dysphonia in 50% of the patients and grade 1 dysphonia (40%) or normal (10%) dysphonia in the remaining ones. Computing analysis revealed the following mean values: fundamental frequency of 177.5 Hz, jitter 1.11%, and shimmer 7.04%. CONCLUSIONS: We conclude that reconstruction with a vestibular fold flap permitted the maintenance of the laryngeal functions of breathing and airway protection during swallowing, as well as the maintenance of phonation function, providing perfect voice emission according to perceptive auditory or acoustic analysis in 1 patient and moderate or severe dysphonia in one half of the cases when technical faults occurred.

Aged↗

Developmental dysphasia: clinical importance and underlying neurological causes.

This survey deals with two aspects of developmental dysphasia which are relevant to child psychiatry; the early diagnosis and treatment of children with developmental dysphasia, which may prevent the progression of learning and behaviour disorders, and the underlying biological causes of this neuro-developmental disorder. The pathophysiology of developmental dysphasia is complex and age-related. In the pre-verbal and early verbal stage, the severity of the clinical picture is primarily determined by concomitant motor pathology (motor dysfunction, dysarthria, general and oral dyspraxia) and by receptive pathology (hearing and auditory perception). In the verbal period, linguistic problems start to play a role, and often combine with oral motor symptoms to present a mixed picture. The various language syndromes do not become clear until some time later. After the kindergarten period, the oral motor and perceptual problems decrease and the language disorders continue to play a role and influence the child's conversation, internal speech and learning a school. In a relatively small number of children without oral motor, perceptual or memory problems, there can be a basic syndrome of "pure dysphasia" without any other neurological signs. These children are very likely to have a genetically determined developmental disorder on a limited neuronal level (no cerebral damage of any kind!) such as an abnormal asymmetry of the hemispheres. In somewhat more than half the patients, this basic syndrome is accompanied by other neurological signs, most of which are indicative of functional disorders of the left hemisphere. There can also be symptoms of the right hemisphere, of the corpus callosum and of the afferent pathway systems for auditory perception. The nature and causes of these anomalies can be multifarious, so that it is unfeasible to speak of THE substrate or THE pathogenesis. Treatment should not be confined to speech therapy techniques, but should also take into consideration the existence of abnormal motor and affective development and can thus only be optimally given by a highly trained team whose expertise also extends to the schooling aspect.

Aphasia↗

Speech pattern hearing aids for the profoundly hearing impaired: speech perception and auditory abilities.

A family of prototype speech pattern hearing aids for the profoundly hearing impaired has been compared to amplification. These aids are designed to extract acoustic speech patterns that convey essential phonetic contrasts, and to match this information to residual receptive abilities. In the first study, the presentation of voice fundamental frequency information from a wearable SiVo (sinusoidal voice) aid was compared to amplification in 11 profoundly deafened adults. Intonation reception was often better, and never worse, with fundamental frequency information. Four subjects scored more highly in audio-visual consonant identification with fundamental frequency information, five performed better with amplified speech, and two performed similarly under these two conditions. Five of the 11 subjects continued use of the SiVo aid after the tests were complete. A second study examined a laboratory prototype compound speech pattern aid, which encoded voice fundamental frequency, amplitude envelope, and the presence of voiceless excitation. In five profoundly deafened adults, performance was better in consonant identification when additional speech patterns were present than with fundamental frequency alone; the main advantage was derived from amplitude information. In both consonant identification and connected discourse tracking, performance with appropriately matched compound speech pattern signals was better than with amplified speech in three subjects, and similar to performance with amplified speech in the other two. In nine subjects, frequency discrimination, gap detection, and frequency selectivity were measured, and were compared to speech receptive abilities with both amplification and fundamental frequency presentation. The subjects who showed the greatest advantage from fundamental frequency presentation showed the greatest average hearing losses, and the least degree of frequency selectivity. Compound speech pattern aids appear to be more effective for some profoundly hearing-impaired listeners than conventional amplifying aids, and may be a valuable alternative to cochlear implants.

Adult↗

Structure of the auditory evoked magnetic fields during sleep.

We studied the effects of sleep on auditory evoked magnetic fields following pure tone stimulation applied to the right ear of 10 healthy normal volunteers to investigate the changes in the processing of auditory perception in the primary auditory cortex. Dual 37-channel biomagnetometers were used to record auditory evoked magnetic fields over the bilateral temporal lobes in response to presented tones. Auditory evoked magnetic fields were compared for three stimulus frequencies (250, 1000 and 4000 Hz) and three sleep stages (awake state, sleep stages 1 and 2). Four main components, M50, M100, M150 and M200, were identified with latencies of approximately 50, 100, 150 and 200 ms, respectively. The latency of each component had a tendency to be prolonged with the depth of sleep stage in all frequencies. The amplitude ratios of the early-latency components (M50 and M100) showed a tendency of reduction compared with the same components in the awake state. By contrast, the amplitude ratios of the long-latency components (M150 and M200) were significantly enhanced with an increase in the sleep stage compared with the same components in the awake state. The equivalent current dipoles of all components in all conditions were detected at the superior temporal cortex (the primary auditory cortex). As for the changes in the equivalent current dipole location of each component, the equivalent current dipole was detected in the more posterior and medial region in responses to the high-frequency tone (1000 and 4000 Hz) compared with those to 250 Hz tone stimulation. Although the equivalent current dipoles of the early-latency components (M50 and M100) were in regions more anterior and superior compared to those in the awake state, there was no consistent tendency of changes in equivalent current dipole locations between each sleep stage in the late-latency components (M150 and M200). These findings are probably due to the difference in generating mechanisms between the early- and late-latency components.

Acoustic Stimulation↗

Cellular studies of auditory hair cell regeneration in birds.

A decade ago it was discovered that mature birds are able to regenerate hair cells, the receptors for auditory perception. This surprising finding generated hope in the field of auditory neuroscience that new hair cells someday may be coaxed to form in another class of warm-blooded vertebrates, mammals. We have made considerable progress toward understanding some cellular and molecular events that lead to hair cell regeneration in birds. This review discusses our current understanding of avian hair cell regeneration, with some comparisons to other vertebrate classes and other regenerative systems.

Animals↗

Visual prosody and speech intelligibility: head movement improves auditory speech perception.

People naturally move their heads when they speak, and our study shows that this rhythmic head motion conveys linguistic information. Three-dimensional head and face motion and the acoustics of a talker producing Japanese sentences were recorded and analyzed. The head movement correlated strongly with the pitch (fundamental frequency) and amplitude of the talker's voice. In a perception study, Japanese subjects viewed realistic talking-head animations based on these movement recordings in a speech-in-noise task. The animations allowed the head motion to be manipulated without changing other characteristics of the visual or acoustic speech. Subjects correctly identified more syllables when natural head motion was present in the animation than when it was eliminated or distorted. These results suggest that nonverbal gestures such as head movements play a more direct role in the perception of speech than previously known.

Adult↗

The effects of production and presentation level on the auditory distance perception of speech.

Although both perceived vocal effort and intensity are known to influence the perceived distance of speech, little is known about the processes listeners use to integrate these two parameters into a single estimate of talker distance. In this series of experiments, listeners judged the distances of prerecorded speech samples presented over headphones in a large open field. In the first experiment, virtual synthesis techniques were used to simulate speech signals produced by a live talker at distances ranging from 0.25 to 64 m. In the second experiment, listeners judged the apparent distances of speech stimuli produced over a 60-dB range of different vocal effort levels (production levels) and presented over a 34-dB range of different intensities (presentation levels). In the third experiment, the listeners judged the distances of time-reversed speech samples. The results indicate that production level and presentation level influence distance perception differently for each of three distinct categories of speech. When the stimulus was high-level voiced speech (produced above 66 dB SPL 1 m from the talker's mouth), the distance judgments doubled with each 8-dB increase in production level and each 12-dB decrease in presentation level. When the stimulus was low-level voiced speech (produced at or below 66 dB SPL at 1 m), the distance judgments doubled with each 15-dB increase in production level but were relatively insensitive to changes in presentation level at all but the highest intensity levels tested. When the stimulus was whispered speech, the distance judgments were unaffected by changes in production level and only decreased with increasing presentation level when the intensity of the stimulus exceeded 66 dB SPL. The distance judgments obtained in these experiments were consistent across a range of different talkers, listeners, and utterances, suggesting that voice-based distance cueing could provide a robust way to control the apparent distances of speech sounds in virtual audio displays.

Adult↗

Assessing auditory distance perception using virtual acoustics.

In most naturally occurring situations, multiple acoustic properties of the sound reaching a listener's ears change as sound source distance changes. Because many of these acoustic properties, or cues, can be confounded with variation in the acoustic properties of the source and the environment, the perceptual processes subserving distance localization likely combine and weight multiple cues in order to produce stable estimates of sound source distance. Here, this cue-weighting process is examined psychophysically, using a method of virtual acoustics that allows precise measurement and control of the acoustic cues thought to be salient for distance perception in a representative large-room environment. Though listeners' judgments of sound source distance are found to consistently and exponentially underestimate true distance, the perceptual weight assigned to two primary distance cues (intensity and direct-to-reverberant energy ratio) varies substantially as a function of both sound source type (noise and speech) and angular position (0 degrees and 90 degrees relative to the median plane). These results suggest that the cue-weighting process is flexible, and able to adapt to individual distance cues that vary as a result of source properties and environmental conditions.

Adult↗