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PubMed2005

Seeing speech affects acoustic information processing in the human brainstem.

Afferent auditory processing in the human brainstem is often assumed to be determined by acoustic stimulus features alone and immune to stimulation by other senses or cognitive factors. In contrast, we show that lipreading during speech perception influences early acoustic processing. Event-related brainstem potentials were recorded from ten healthy adults to concordant (acoustic-visual match), conflicting (acoustic-visual mismatch) and unimodal stimuli. Audiovisual (AV) interactions occurred as early as approximately 11 ms post-acoustic stimulation and persisted for the first 30 ms of the response. Furthermore, the magnitude of interaction depended on AV pairings. These findings indicate considerable plasticity in early auditory processing.

Acoustic Stimulation↗
PubMedDate not supplied

Acoustic versus phonetic representation of speech as reflected by the mismatch negativity event-related potential.

The concept of categorical perception of speech and speech-like sounds has been central to models of speech perception for decades. Event-related potentials (ERPs) provide a neurophysiologic perspective of this important phenomenon. In the present experiment the mismatch negativity (MMN) event-related potential, which is sensitive to fine acoustic differences, was recorded in adults. Of interest was whether the MMN reflects the acoustic or categorical perception of speech. The MMN was elicited by stimulus pairs (along a continuum varying in place of articulation from /da/ to /ga/) which had been identified as the same phoneme /da/ (within category condition) and as different phonemes /da/ and /ga/ (across categories condition). The acoustic differences between these two pairs of stimuli were equivalent. The MMN was observed in all subjects both in the within and across category conditions. Furthermore, the MMN did not differ in latency, amplitude or area within and across categories. That is, the MMN indicated equal discrimination both across and within categories. These results suggest that the MMN appears to reflect the processing of acoustic aspects of the speech stimulus, but not phonetic processing into categories. The MMN appears to be an extremely sensitive electrophysiologic index of minimal acoustic differences in speech stimuli.

Acoustic Stimulation↗
PubMed2005

Callus mineralization following distraction osteogenesis of the mandible monitored by scanning acoustic microscopy (SAM).

BACKGROUND: Scanning acoustic microscopy uses ultrasound to analyse histomorphology of tissues with microscopic resolution and delivers data about physical properties of the specimen. MATERIAL AND METHODS: Bony consolidation was monitored by scanning acoustic microscopy in 12 embedded specimens of dog mandibles after distraction osteogenesis. Increasing mineralization was detected by measurements of acoustic impedance (Z). RESULTS: There was a strong correlation between acoustic impedance and time of consolidation. Measurements of the speed of sound (v) provided specific information about non-mineralized zones of the distracted area. Distribution of density in the distracted area could be reconstructed by using the measurements of acoustic impedance and speed of sound. CONCLUSION: The method seems suitable for studying bone remodelling qualitatively and quantitatively.

Acoustics↗
PubMed1981

The effects of aging on the magnitude of the acoustic reflex.

Aural acoustic-immittance (admittance and impedance) measurements during the quiescent and reflexive states were made using a computer sampling technique on 18 subjects with normal hearing in each of two age groups (less than 30 years and greater than 50 years). Seven pure-tones (250-6000 Hz) and broadband-noise stimuli served to elicit the acoustic reflex at sound-pressure levels from 84-116 dB (tones) and 66-116 dB (noise) in 2-dB steps during ascending and descending runs. The contralateral middle-ear activity was monitored with a 220-Hz probe by digitizing the conductance and susceptance outputs of an acoustic-admittance meter. The computer corrected for the immittance characteristics of the ear-canal volume by utilizing measurements made at an ear-canal pressure of -350 daPa and then by converting the conductance and susceptance values into admittance and impedance units. The results are reported as the immittance change between the quiescent and reflexive states as a function of both the activator sound-pressure level and the activator-pressure level above the reflex threshold. There were no significant differences between the static-immittance values for the two groups. Although acoustic-reflex thresholds for the two groups were the same in the low- to mid-frequency region (250-2000 Hz), the reflex thresholds for the greater than 50-years group were elevated significantly (approximately 8 dB) for 4000 Hz, 6000 Hz, and noise activators. In all conditions, the magnitude of the acoustic reflex was substantially smaller for the greater than 50-years group as compared with the less than 30-years group. The variability of the reflex magnitude was large for both groups of subjects. Saturation of the individual growth functions, which was frequency dependent, occurred twice as often with the greater than 50-years group as with the less than 30-years group. The relationship between the magnitude changes in conductance and susceptance from the quiescent to the reflexive state was the same for the two groups. Finally, the magnitude differences among the reflex-growth data were not related to differences in static immittance.

Acoustic Impedance Tests↗
PubMed1998

Effect of probe frequency and gender on click-evoked ipsilateral acoustic reflex thresholds.

This study was designed to evaluate the effects of gender and probe frequency on the ipsilateral click-evoked acoustic reflex thresholds. Ipsilateral acoustic reflex thresholds were obtained from the left ear of each subject (12 male and 12 female normal young adults) by presenting clicks at the rate of 180/sec. The probe tone frequencies were 226, 678 and 1.000 Hz. The results revealed that acoustic reflex thresholds for the 678 Hz probe were significantly higher than those obtained with the 226 and 1.000 Hz probes. No gender differences were apparent. However, the static admittance was significantly correlated with the acoustic reflex thresholds for the 678 Hz probe in only the female subjects. For the 226 Hz probe, the elicitation of the reflex resulted in a decrease in static admittance in all the subjects. For the 678 Hz probe, the admittance decreased in 58% of the subjects and it increased in 42% of the subjects. For the 1,000 Hz probe, an increase in admittance was apparent in all of the subjects. The results suggest that either the 226 Hz or the 1,000 Hz probes can be used for the measurement of click-evoked acoustic reflex thresholds in adults.

Acoustic Impedance Tests↗
PubMed2006

The effects of childhood otitis media on the acoustic reflex threshold at age 15.

Previous research has found that childhood otitis media leads to elevated adulthood acoustic reflex thresholds because of worsened audiometric thresholds in the stimulation ear, and abnormality of the tympanic membrane in the ear from which acoustic reflexes were measured. To confirm and expand this finding, our research utilized longitudinal data from 631 general-population-sampled children assessed between ages 5 and 15. Otitis media was assessed to age 9, audiometric thresholds were measured at age 11, and otoscopy and acoustic reflex thresholds testing were performed at age 15. Our findings support the earlier research, in that acoustic reflex threshold was higher in those with the worst experience of childhood otitis media. However, this was directly mediated not by audiometric threshold in the ear to which the stimulus was delivered, but by the amount of tympanic membrane abnormality in both the stimulus and probe ears. This appeared to have an effect independent of audiometric threshold. Furthermore, only those who suffered the worst, persistent, binaural childhood otitis media showed raised acoustic reflex thresholds.

Acoustic Impedance Tests↗
PubMedDate not supplied

High-frequency sensitization of the acoustic reflex.

High-frequency sensitization of the acoustic reflex was studied in 10 normal-hearing subjects. The procedure involved pairing a subreflex 6000 Hz sensitizing tone with activating frequencies of 500, 1000, and 2000 Hz. Both threshold and growth of amplitude of the acoustic reflex were examined. Acoustic reflex threshold was reduced by an average of 10 to 12 dB in the presence of a 6000 Hz sensitizing tone, an amount significantly less than previously reported in similar investigations. Variations in the method used to adjust the presentation level of the high-frequency sensitizing tone probably account for these differences. Growth of acoustic reflex amplitude was also found to be influenced by sensitizing stimulation, with the greatest effect occurring near acoustic reflex threshold.

Acoustic Stimulation↗
PubMedDate not supplied

The time course of the acoustic reflex.

The time course of the impedance changes caused by the contralateral acoustic reflex was investigated in five normal hearing, young adult subjects The acoustic reflex function was measured with equipment having a time constant of 15 milliseconds which permitted precise temporal measures. Temporal intervals from signal onset and termination to various portions of the acoustic reflex function were derived using an analysis procedure based on the slope function underlying the acoustic reflex response. These temporal intervals are related to physiological events underlying the acoustic reflex.

Acoustic Stimulation↗
PubMed2005

Reversed ipsilateral acoustic reflex: a study on subjects treated with muscle relaxants.

OBJECTIVES: To rule out any possible involvement of the middle ear muscles in the genesis of the reversed ipsilateral acoustic reflex (RIAR). DESIGN: Prospective study to evaluate the effects of muscle relaxants on the RIAR of otosclerotic ears as well as on the acoustic reflex of individuals with normal middle ear function. Admittance recording during ipsilateral acoustic stimulation was performed in patients undergoing pharmacological treatment for surgical procedures. Fentanyl, propofol, and a muscle relaxant were sequentially administered intravenously. Ipsilateral acoustic reflexes were recorded before and after each drug injection. Three patients were affected from otosclerosis, whereas 14 individuals had normal middle ear function. Moreover, the ipsilateral acoustic reflex obtained in normal subjects after their treatment with muscle relaxants was compared with that of 10 otosclerotic patients who were not treated pharmacologically. RESULTS: The RIAR of three otosclerotic ears was not inhibited by muscle relaxants as well as by fentanyl and propofol. Moreover, muscle relaxants, when administered in normal subjects, always induced the block of the stapedial reflex that was replaced by a reversed reflex strictly similar to the RIAR of the 10 otosclerotic patients not treated pharmacologically. Propofol could also induce, in most of the cases, the reduction and in some occasion even the reversal of the stapedial reflex, whereas fentanyl did not affect it significantly. CONCLUSION: The RIAR does not appear to be related to the contraction of the middle ear muscles.

Acoustic Stimulation↗
PubMed2004

Mobile phone use and the risk of acoustic neuroma.

BACKGROUND: Radiofrequency exposure from mobile phones is concentrated to the tissue closest to the handset, which includes the auditory nerve. If this type of exposure increases tumor risk, acoustic neuroma would be a potential concern. METHODS: In this population-based case-control study we identified all cases age 20 to 69 years diagnosed with acoustic neuroma during 1999 to 2002 in certain parts of Sweden. Controls were randomly selected from the study base, stratified on age, sex, and residential area. Detailed information about mobile phone use and other environmental exposures was collected from 148 (93%) cases and 604 (72%) controls. RESULTS: The overall odds ratio for acoustic neuroma associated with regular mobile phone use was 1.0 (95% confidence interval = 0.6-1.5). Ten years after the start of mobile phone use the estimates relative risk increased to 1.9 (0.9-4.1); when restricting to tumors on the same side of the head as the phone was normally used, the relative risk was 3.9 (1.6-9.5). CONCLUSIONS: Our findings do not indicate an increased risk of acoustic neuroma related to short-term mobile phone use after a short latency period. However, our data suggest an increased risk of acoustic neuroma associated with mobile phone use of at least 10 years' duration.

Acoustic Stimulation↗
PubMed2005

Acoustic and spectral characteristics of young children's fricative productions: a developmental perspective.

Scientists have made great strides toward understanding the mechanisms of speech production and perception. However, the complex relationships between the acoustic structures of speech and the resulting psychological percepts have yet to be fully and adequately explained, especially in speech produced by younger children. Thus, this study examined the acoustic structure of voiceless fricatives (/f, theta, s, S/) produced by adults and typically developing children from 3 to 6 years of age in terms of multiple acoustic parameters (durations, normalized amplitude, spectral slope, and spectral moments). It was found that the acoustic parameters of spectral slope and variance (commonly excluded from previous studies of child speech) were important acoustic parameters in the differentiation and classification of the voiceless fricatives, with spectral variance being the only measure to separate all four places of articulation. It was further shown that the sibilant contrast between /s/ and /S/ was less distinguished in children than adults, characterized by a dramatic change in several spectral parameters at approximately five years of age. Discriminant analysis revealed evidence that classification models based on adult data were sensitive to these spectral differences in the five-year-old age group.

Acoustic Stimulation↗
PubMed2003

Acoustic neuroma in patients with completely resolved sudden hearing loss.

Approximately 30% of patients with sudden hearing loss show complete recovery. Researchers have long questioned whether extensive evaluation is necessary in these cases. Recently, however, with the increasing widespread application of magnetic resonance imaging, a higher rate than expected of acoustic neuromas has been detected in patients with sudden hearing loss. Two studies have suggested that affected patients may even partially regain hearing. The aim of the present clinical study was to determine whether acoustic neuroma-induced hearing loss may be associated with full recovery. The files of 67 patients evaluated for sudden hearing loss at Rabin Medical Center from 1989 to 2000 were reviewed. All patients underwent pure tone audiometry, acoustic reflex tests, and auditory brain stem evoked response tests. Hearing evaluation was followed by magnetic resonance imaging scan and, 1 month later, a second hearing test. Findings were compared between patients with and without evidence of tumor on imaging, and between patients with tumor with and without full recovery. Twenty-four patients (36%) had a diagnosis of acoustic tumor, of whom 4 (16.7%) recovered hearing after 1 month. All 4 tumors were intracanalicular. Two of these patients had low-tone hearing loss, and 2 had flat curves; 3 had a pathological auditory brain stem evoked response. Of the 43 patients without tumors, 26 (60%) showed complete resolution of the hearing loss. We conclude that complete recovery of hearing loss does not exclude acoustic tumor, and these patients therefore require full evaluation. The reason for the recovery remains unclear.

Audiometry, Evoked Response↗
PubMed1984

Transcranial conduction of acoustic-reflex-eliciting signals.

Conduction of a broad-band signal from a supra-aural earphone to an acoustic-immittance instrument coupled to the contralateral ear canal was studied using three commercial immittance instruments. Results indicated that portions of the broad-band signal reached the contralateral ear canal at presentation levels of 100-110 dB SPL. At levels as low as 100 dB SPL, the signal was detected by at least one of the acoustic-immittance instruments. At higher sound pressure levels the transmitted signal caused deflections of the acoustic-immittance meter similar to those associated with an acoustic-reflex response. However, these artifacts could be differentiated from acoustic-reflex responses in several respects and could be prevented by high-pass filtering of the broad-band test signal.

Acoustic Impedance Tests↗
PubMedDate not supplied

[The stapes reflex in acoustic tumors (92 cas) (author's transl)].

A comparative study of the acoustic reflex in 92 cases of acoustic neuromas and 40 otological syndromes with a normal meatography. There was complete deafness in 22% of the acoustic neuroma cases and 7.5% of the "false neuromas". A deafness less than 75 dB was observed in 72 VIII nerve and 37 "false neuroma cases, where the acoustic reflex was studied: --reflex absent in 29% of VIII nerve and 11% of "false neuromas"; --decay of reflex in 22% of VIII nerve and 5% of "false neuromas"; --non-pathological reflex in 17% of VIII nerve and 30% of "false neuromas". Hearing was preserved post-operatively in 19 cases out of 55 operations (the retro-sigmoid and middle fossa routes). The acoustic reflex without Decay is an element two times more favourable than a reflex with Decay in cases with preserved hearing.

Adult↗
PubMedDate not supplied

[The use of short-latency auditory evoked potentials in the diagnosis of acoustic neurinomas].

The short-latent acoustic evoked potentials in patients with unilateral neurosensory hypoacusis due to the tumor of the acoustic nerve or other etiology were recorded. It was found that the patients had no potential in the diseased area in monaural sound stimulation, but binaural sound stimulation enabled these potentials to be recorded. With this, the short-latent acoustic evoked potentials in patients with verified neurinoma showed a reduction in the third wave to the point of its disappearance. Those in patients whose neurosensory hypoacusis were unassociated with the development of neoplasms in the area of the acoustic nerve involve the third wave whose magnitude did not differ from that recorded in the examinees with otologically normal hearing. The authors propose to measure the third wave of the short-latent acoustic evoked potential recorded in binaural sound stimulation as a possible screening of persons at a high risk for neurinoma among patients with unilateral neurosensory hypoacusis.

Acoustic Stimulation↗
PubMed2000

Gamma knife radiosurgery as a primary treatment for prolactinomas.

OBJECT: The purpose of this study was to estimate the efficacy of gamma knife radiosurgery (GKS) in controlling tumor growth and endocrinopathy associated with prolactinomas. METHODS: Between 1993 and 1997, 164 of 469 patients with pituitary adenomas treated by GKS harbored prolactinomas. The dose to the tumor margin ranged from 9 to 35 Gy (mean 31.2 Gy), and the visual pathways were exposed to a dose of less than 10 Gy. The mean tumor diameter was 13.4 mm. The mean follow-up time for 128 cases was 33.2 months (range 6-72 months). Tumor control was observed in all but two patients who underwent surgery 18 and 36 months, respectively, after GKS. Clinical cure was achieved in 67 cases. Clinical improvement was noted with a decrease in the hyperprolactinemia after GKS. Nonetheless, in 31 (29%) of 108 patients who were followed for more than 2 years no improvement in serum prolactin levels was demonstrated, although this could be normalized by bromocriptine administration after treatment. Nine infertile women became pregnant 2 to 13 months after GKS and all gave birth to normal children. There was no visual deterioration related to GKS. Five women experienced premature menopause. In these patients there was subtotal disappearance of the tumor and an empty sella developed. CONCLUSIONS: Gamma knife radiosurgery as a primary treatment for prolactinomas can be safe and effective both for controlling tumor growth and for normalization of prolactin hypersecretion. A higher margin dose (> or = 30 Gy) seemed to be associated with a better clinical outcome. Gamma knife radiosurgery may make prolactinomas more sensitive to the bromocriptine.

Humans↗
PubMed1978

Acoustic impedance and otoscopic findings in young children with Down's syndrome.

This study sought to determine the point incidence of middle ear pathologic conditions and to ascertain the value of acoustic impedance-admittance measurements in detecting otitic pathologic conditions in young children with Down's syndrome. Pneumo-otoscopy and acoustic impedance measures were performed on 38 children (mean age, 3.1 years) with Down's syndrome. Results indicated that more than 60% of the series demonstrated otoscopic and acoustic impedance evidence of middle ear effusion, which is in keeping with results reported previously for older children and young adults with Down's syndrome. Of particular interest was the large number of normal ears that displayed absent crossed and uncrossed acoustic reflexes,which suggested that measurement of the acoustic reflex may be an unreliable parameter for confirming the presence of middle ear effusion in children with Down's syndrome. To maximize the educational potential of these children, a careful examination to detect middle ear effusion must be performed at periodic intervals. If persistent effusion is detected, appropriate surgical management should be instituted without delay.

Acoustic Impedance Tests↗
PubMed1980

The hyperactive acoustic reflex. Four case studies.

Four case studies are presented to illustrate that low acoustic reflex thresholds may have value in assessment of central auditory processing disorders. Neurologic, electronystagmographic, EEG, speech pathologic, and/or psychological evaluations suggested CNS impairment. Tests for central auditory processing disturbances were positive. For three subjects, acoustic reflex responses were elicited at unusually low hearing threshold levels. A fourth subject showed lowering of acoustic reflex thresholds following bilateral electroshock treatment. These lowered thresholds were interpreted as hyperactive acoustic reflex responses representing a decreased central inhibition on peripheral auditory function. It is proposed that presence of hyperactive acoustic reflex responses may be associated with a concomitant central auditory processing disorder.

Aged↗