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At least 19 recordsLinked to original sources
PubMedDate not supplied

Adaptation of the acoustic reflex.

Acoustic reflex adaptation is reviewed in normal and abnormal auditory systems. The measurement variables affecting the acoustic reflex threshold are discussed with reference to the intensity level above reflex threshold at which the adaptation is measured. The effects of the activator frequency and activator intensity level on the time course of normal reflex adaptation are reviewed. The diagnostic application of acoustic reflex adaptation is discussed with reference to the different definitions of abnormality found in the literature. The acoustic reflex patterns, including absence, threshold, and adaptation of the reflex, are reported in patients with different degrees of hearing loss, in order to identify the false-positive rates associated with cochlear hearing losses. Finally, the diagnostic accuracy of acoustic reflexes is discussed in subjects having lesions of the CNVIII, brain stem, CNVII, and neuromuscular systems. In summary, a method is advocated for measuring acoustic reflex adaptation over 10 seconds, which allows analysis at both 5 and 10 seconds. Further research is needed on procedural variables including activator intensity level and ipsilateral recording methods, which may increase the diagnostic accuracy of acoustic reflex adaptation.

Adaptation, Physiological↗
PubMed1987

Early development of the acoustic reflex.

Acoustic reflex testing was conducted on 2-day-old and on 6-week-old infants to determine how frequently, if at all, the acoustic reflex occurs, if it can be reliably observed, and also to determine what is the mean normal acoustic reflex threshold for pure tones and broad-band noise in these populations. Twenty normal infants were tested in each group. Each infant was considered to be normal by the following criteria: full term, normal pregnancy normal pregnancy and delivery, birth weight greater than 2500 g, 5-min Apgar of 7 or greater, and considered to be not at risk for hearing loss by the absence of any high risk factors. Subjects were tested following feedings. Acoustic reflexes were obtained from subjects with normal tympanograms (+/- 50 mm H2O) for 500, 1,000, 2,000, and 4,000 Hz and broad-band noise stimuli. Behavioral responses were common, requiring quieting pauses in testing and repeated stimulation for habituation of the behavioral component. Acoustic reflexes were observed, and normative reflex threshold data were obtained. The number of reflexes obtained and the mean acoustic reflex thresholds for these age-groups are reported.

Acoustic Impedance Tests↗
PubMedDate not supplied

[Effect of noise on changes in the acoustic reflex].

Acoustic, stapedial reflex represents a response of the m. stapedius to a sonic excitation of supra speech intensity. It is the constitutive part of impendancmetric investigations, it is performed on the same apparatus after tympanometry, and it is the inseparable part in representation of impendancmetric findings. Until now, the most frequently monitored parameters of acoustic reflex of clinical importance are: threshold, amplitude, output and input angle of the reflex curve. The aim of this work was to performed detailed analysis of mentioned parameters in workers exposed to extensive action of industrial noise of known physical characteristics (of different durations) and to establish which changes occurred in these workers, to what extent and under which conditions. Investigations included 173 industrial workers (346 ears), which work in working unit "Forge", where during the working process noise is produced which is above permissible limits and of the unfavorable frequency content. Workers were divided into two groups. The first group consisted of workers who were spending the whole working time in the workroom with noise above permissible limits, the second group consisted of workers who were spending 3 hours of the working time in that workroom, while the control group consisted of workers who were spending the whole working time in that workroom but they did not have any hearing impairment. Workers of the first and the second group had the hearing impairment, which occurred exclusively as a consequence of chronical acoustic trauma. For all the workers the anamnesis was taken, as well as ORL status and audiometric and impendancmetric investigations were performed, namely the tympanometry and acoustic reflex. Results have shown that the acoustic reflex threshold at 500 Hz and at 1000 Hz for the first group (95.10 dB) was increased with respect to the reflex threshold of the second and the control group (84 dB). At higher frequencies of 2000 Hz and 4000 Hz an increase of the reflex threshold was found for the first and the second group (96 dB) with respect to the control group (87 dB). The amplitude of acoustic reflex was increased, at frequencies 500 Hz and 1000 Hz (3.38), with respect to the second group (2.78) and the control group (2.36), and at higher frequencies, this increase is more prominent. The input angle of the reflex curve was, for the first and the second group, within limits 41 degrees to 50 degrees, and for the control group was from 31 degrees to 50 degrees. The output angle was, at majority of ears of the first and the second group, from 26 degrees to 35 degrees, and for the control group it was from 16 degrees to 35 degrees. Acoustic reflex, as the noninvasive method, short term one, objective and simple for application, does not require collaboration of workers, what provides for objectivity of obtained results and what caused that wrongful estimations, impressions and subjective reactions of workers were avoided.

Hearing Loss, Noise-Induced↗
PubMedDate not supplied

Effect of eye closure, mental concentration, and nonauditory sensory stimulation on the threshold and magnitude of the acoustic reflex.

Acoustic reflex threshold and magnitude were measured for normal-hearing subjects in four experiments under conditions of: (1) tight and relaxed eyelid closure; (2) eyes open and closed in light, focusing on a spot, reading, and solving a visual maze; (3) tactile stimulation; and (4) performing a mental task. Measurements were susceptance change in millimhos for a 220 Hz probe tone. A 1000 Hz pure-tone and broadband noise presented contralaterally were the stimuli. All factors affected reflex results. Eyelid closure enhanced reflex responses with tight closure involving voluntary muscle tension having a greater effect than relaxed closure. Both passive and active visual tasks suppressed the reflex. The mental task resulted in suppression of both reflex threshold and magnitude. Vibrotactile stimulation also resulted in a suppressed reflex. Changes were more pronounced with broadband noise as the reflex eliciting stimulus. Clinical implications are discussed.

Adult↗
PubMed2003

Diagnostic potential of acoustic startle reflex, acoustic blink reflex, and electro-oculography in progressive supranuclear palsy: a prospective study.

We carried out a prospective study to analyze the diagnostic potential of acoustic startle reflex (ASR), acoustic blink reflex (ABR) and electro-oculography (EOG) in early stages of atypical parkinsonian syndrome. The study was carried out in a consecutive series of 41 patients clinically diagnosed as atypical parkinsonism (mean time from first symptoms of 38 months and follow-up of 26 months). The three procedures were carried out immediately after the first clinical evaluation. ASR and ABR were elicited by auditory stimuli while the patient was attending to a simple reaction time task. Outcome measures were: ASR (absence/presence, latency), ABR (absence/presence, latency) and EOG (suggestive/not suggestive of progressive supranuclear palsy [PSP]). Final clinical diagnosis was carried out by two neurologists blind to the neurophysiological results. A study of diagnostic sensitivity and odds ratio (OR) calculation for the PSP diagnosis was carried out. Neurophysiological examination showed the following sensitivity/specificity (%) for the diagnosis of PSP: ASR: 100/89; ABR 85/89; EOG 100/72. OR values were: ASR: 0.011; ABR: 0.037; EOG: 0.038. The three tests taken simultaneously showed a sensitivity of 100% and a specificity of 95%. The three neurophysiological tests investigated provided sensitive and specific measures with predictor value in early stages of atypical parkinsonian syndrome.

Aged↗
PubMed1984

Developmental norms for the acoustic reflex.

Acoustic reflexes were observed in 45 infants between the ages of 12 and 36 weeks. As age increased, smaller ranges of signal levels were needed to elicit the reflex and less intensity was required, but a noise stimulus did not show age-related changes. Stimulus frequency was not a source of variation of response. The reflex arc has undergone maturation by 12 weeks of age and continues to mature to 36 weeks.

Acoustic Impedance Tests↗
PubMedDate not supplied

Effects of ear canal pressure on threshold and growth of the acoustic reflex.

Acoustic reflex (AR) threshold and growth were measured in one ear for each of 20 normal-hearing individuals as pressure in the ear canal was varied between +/- 120 mm of H2O. These same parameters were studied in 10 of the subjects after disruption of the probe seal. Activating stimuli for AR threshold measures were 500, 1000, 2000, and 4000 Hz tones and broadband noise. The AR growth function was generated by a 500 Hz tone. As ear canal pressure was increased or decreased relative to the point of maximal compliance, systematic increases in AR threshold were observed for all activating stimuli. These mean pressure effects were relatively small (4 to 8 dB) and were essentially independent of stimulus composition. The ear canal pressure variations had no effect on the relative difference between tone and broadband noise AR thresholds. Absence of an airtight seal had a negligible effect on AR threshold. Growth of the AR was significantly altered by application of a relatively mild positive or negative canal pressure. Absence of a probe seal which had no effect on AR threshold was found to significantly reduce magnitude of the AR. These findings indicate that caution should be exercised during the measurement of AR growth to ensure both proper maintenance of desired canal pressure and canal-probe coupling.

Acoustic Impedance Tests↗
PubMed1996

Effect of aging on the click-rate induced facilitation of acoustic reflex thresholds.

Acoustic reflex thresholds are known to improve with an increase in the click-repetition rates from 50/sec to 300/sec. In the current study this improvement was used to evaluate auditory processing in older subjects. Acoustic reflex thresholds were obtained from 16 human adult ears within each of the following four groups: young male, young female (18-28 years), older male and older female (50-65 years). The probe tone frequency was 226 Hz and the intensity of the probe tone was 85 dB SPL (sound pressure level). Clicks were delivered ipsilaterally to each ear at repetition rates of 50, 100, 150, 200, and 300/sec. The mixed MANOVA revealed a significant effect for the repetition rate and a significant age and rate interaction. Rate integration in dB was computed by subtracting the highest acoustic reflex threshold from the lowest threshold of each ear. Statistical analyses revealed reduced rate integration in the older subjects, suggesting less efficient processing of faster stimuli within the acoustic reflex pathway.

Adolescent↗
PubMedDate not supplied

Recovery characteristics of the acoustic reflex.

Acoustic-reflex recovery time was measured as a function of activator intensity level and duration for broad-band noise and a 500-Hz tone in 10 normal-hearing subjects. The activating signals were presented at 5 and 10 dB above individual acoustic reflex thresholds for durations ranging from 0.25 to 100 sec. Reflex-recovery times were similar across both activators and across activator intensity levels. Recovery time was relatively constant for activators of 2 sec or less and increased for longer activator durations. Portions of the results from temporary threshold shift experiments are explained on the basis of acoustic reflex recovery characteristics.

Acoustic Stimulation↗
PubMedDate not supplied

Quantification of the relationship between crossed and uncrossed acoustic reflex amplitudes.

Acoustic reflex amplitude data were obtained for 92 subjects. Uncrossed (ipsilateral) and crossed (contralateral) acoustic reflex activity was measured simultaneously and computer averaged with specially constructed apparatus. For all subjects, amplitude was greater for uncrossed than crossed acoustic reflexes. The ratio of maximum uncrossed versus crossed reflex amplitude for young normal-hearing subjects ranged from 1.06 to 2.38, with an average of 1.50. This relationship was not significantly influenced by subject age, sensorineural hearing impairment, or mild abnormalities in acoustic immittance. Clinical investigation of the diagnostic application of the uncrossed versus crossed reflex amplitude ratio in central auditory nervous system pathology is suggested.

Adult↗
PubMedDate not supplied

Effects of ethyl alcohol on the acoustic reflex threshold.

Acoustic reflex thresholds for pure tones and white nose were measured every 20 min for 4 hr after the ingestion of ethyl alcohol. The average maximum acoustic reflex threshold shift was 11 dB, occurring on the average at 100 min, and returning to base-line levesl at approximately 200 min postingestion. These data lend support to the classification of ethyl alcohol as a sedative, and should caution the clinician when interpreting acoustic reflex threshold data from persons who have ingested small amounts of alcohol.

Adult↗
PubMedDate not supplied

Note on identification and rectification of the "overshoot" observed with the Grason-Stadler otoadmittance meter during acoustic reflex measurements.

Acoustic reflexes measured with the Grason-Stadler 1720 otoadmittance meter exhibit an artefactual overshoot due to the transient response characteristics of the instrument. Additional circuitry has been developed to overcome this problem. It allows the temporal characteristics of the acoustic reflex to be recorded accurately without this artefact.

Bone Conduction↗
PubMed1979

Multiple probe frequency acoustic reflex measurements.

Acoustic reflex impedance measurements are made on forty-seven normal and two otosclerotic ears using fixed probe frequencies from 220 to 2000 Hz. In general, the reflex increases the middle ear impedance up to 700 Hz probe frequency and decreases it thereafter. It is postulated that this characteristic is related to removal of the cochlear fluid resistance due to stapes decoupling. At one probe frequency in the range 500--900 Hz, the reflex of 50% of the normal ears has either a diphasic pattern or shows no change in the impedance vector length. The accompanying phase change is always monophasic. In the otosclerotic ear the diphasic reflex is present for every probe frequency. These factors should be taken into account when probe frequencies greater than 220 Hz are used for reflex measurement.

Acoustic Impedance Tests↗
PubMed1983

Evaluation of tensor tympani muscle dominance in the biphasic acoustic reflex.

The Acoustic reflex frequently causes a biphasic change in impedance at onset. Understanding the cause of the biphasic response is important for establishing a physiological basis for the clinical measurement of reflex latency. The decrease in impedance at onset may be due to uncoupling of impedance contributed by the cochlea. Subsequent increases in impedance predominantly reflect stapedius muscle activity. The clinical implications of this physiologic model are discussed.

Acoustic Impedance Tests↗
PubMed1981

Dynamics of acoustic reflex growth.

Acoustic reflex growth was measured as a function of activator bandwidth in 10 subjects with normal hearing and in 5 subjects with different configurations of sensorineural hearing loss. The activators consisted of tones with frequencies of 500, 1 000 and 4 000 Hz, fractions and multiples of octave bands centered at these frequencies, and broadband noise. Growth functions for the normal-hearing subjects measured with a 660-Hz probe tone had smaller peak magnitudes and shallower slopes than the growth functions measured with a 220-Hz probe tone. The slope of the growth function and the peak magnitude of acoustic impedance were not affected in any consistent manner by activator bandwidth or activator center frequency. The dynamic range of the growth function increased with an increase in activator bandwidth beyond 1 octave. The resistive component of acoustic impedance did not exhibit a consistent pattern of change with increasing activator intensity level. The reflex growth functions for normal-hearing subjects separated into two groups, those with steep slopes and large peak magnitudes and those with shallow slopes and small peak magnitudes. 3 out of the 5 cases with sensorineural hearing loss presented growth functions with shallower slopes, smaller dynamic ranges and smaller peak magnitudes than normal. The other 2 cases had steeper slopes and larger peak magnitudes than normal. The dynamic range did not increase with an increase in activator bandwidth beyond 1 octave. The differences in reflex growth functions with probe-tone frequency observed for the normal group were diminished or absent in 4 of the 5 cases of sensorineural hearing loss. The frequency of 4 000 Hz appeared to be the most sensitive to reflex manifestations of hearing loss.

Acoustic Impedance Tests↗
PubMed1979

A systematic investigation of measurement parameters of acoustic-reflex adaptation.

Acoustic-reflex adaptation was assessed in 49 normal ears. Acoustic reflexes were elicited by the use of contralateral stimulation at four frequencies and five sensation levels. The results displayed the effects of stimulus frequency and sensation level on the amount of acoustic-reflex adaptation. Suggestions are presented for clinical procedures for obtaining contralateral acoustic reflex adaptation measures.

Acoustic Stimulation↗