Stapedius reflex and monaural masking.
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Acoustic Stimulation↗
Biomedical subjects
E Borg
Publications and source records attributed to E Borg.
Synaptic vesicles in the cochlea.
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Animals↗
The acoustic impedance change as a measure of stapedius muscle activity in man. A methodological study with electromyography.
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Acoustic Stimulation↗
Auditory fatigue in patients with stapedius muscle paralysis.
Experiments were performed in 18 patients with peripheral facial palsy (Bell's palsy) including unilateral stapedius muscle paralysis. After exposure to narrow band noise centered at 0.5 kHz temporary threshold shift at 0.75 kHz was significantly higher in the ear with paralysis than in the normal ear. After exposure to 2.0 kHz narrow band noise there was no difference in TTS at 3.0 kHz between affected and non-affected ear. It was concluded that the stapedius reflex has a protective function against low frequency sound exposure and suggested that this protection might be extended to higher frequencies only when high frequency noise also contains low frequency components.
Acoustic Stimulation↗
The activity of the stapedius muscle in man during vocalization.
The EMG of the stapedius muscle and visible movements in the stapedius tendon during the subject's own vocalization of an [a:] and during contralateral acoustic stimulation were studied in subjects with eardrum perforation. The threshold for stapedius activity was near the lowest vocal intensity that the subjects could produce. At normal vocal effort the stapedius muscle was activated to about 50% of its maximum value. The EMG often started before the vocal sound, indicating that the stapedius muscle can be activated from the central nervous system as a part of the vocalization process. It is suggested that the contraction of the stapedius muscle during vocalization reduces the masking caused by the low frequency components of the person's own voice even at normal vocal effort and thereby improves intelligibility of simultaneous external speech.
Acoustic Stimulation↗
Peripheral vasoconstriction in the rat in response to sound. I. Dependence on stimulus duration.
Vasoconstriction in response to sound has been studied in the non-anaesthetized rat. Arterial pulsations in the tail were recorded by a non-invasive technique. Broad-band noise bursts at 80 dB SPL with durations from 1 ms to several hours were presented in a free field in a sound-isolated box. The results show that acoustic energy is integrated with a time constant of about 0.1 s. The responses during continuous stimulation habituated slowly and the time to halfway normalization of arterial pulsation was more than 15 min.
Acoustic Stimulation↗
Peripheral vasoconstriction in the rat in response to sound. II. Dependence on rate of change of sound level.
Vasoconstrictions elicited by sound were studied in the non-anaesthetized rat. Arterial pulsations in the tail were recorded by a non-invasive technique. On slightly heating the animal, the tail vessels became dilated. An 80 dB SPL noise burst caused a decrease in pulse amplitude, usually to less than 10% of the pre-stimulus value. It was found that 4 s bursts of 80 dB SPL noise with rise times 1, 10, or 100 ms were equally efficient in producing vasoconstriction. If the rise time was longer, 1 s, the vasconstriction was significantly smaller. It was pointed out that the feedback control of the stimulus noise provided by the acoustic middle ear reflex would contribute to enhancing rapid variations in sound level, and thereby form part of a physiological explanation for the present findings.
Acoustic Stimulation↗
Peripheral vasoconstriction in the rat in response to sound. III. Dependence of pause characteristics in continuous noise.
The peripheral vascular reaction to sound was studied in the non-anaesthetized rat. Arterial pulsations were recorded by a non-invasive technique from the tail of the animal. The offset of a noise was found to be a weak stimulus for vasoconstriction, eliciting responses in only half of the presentations. A vasoconstriction was, however, regularly elicited by onset of sound after the end of the pause. The vasoconstriction was independent of pause duration in the range 10 ms to 100 s. For shorter pauses the reaction was smaller; It was especially noted that a 10 ms pause gave a larger response than a 10 ms burst of noise. The results were discussed in relation to decay of sensation and partial masking effects.
Acoustic Stimulation↗
Decay and recovery of the acoustic stapedius reflex in humans.
The time course of decay and recovery of ipsilateral and contralateral stapedius reflex responses to 2 000 Hz pure tone stimulation was studied in 10 normal-hearing subjects. Reflex responses were found to follow a closely similar time course with respect to both decay and recovery in simultaneous bilateral recordings. The similarity is compatible with the assumption that decay and recovery originate in the afferent auditory system, and not in the muscles. Recovery was 50% complete 250 ms after the end of the stimulus and most subjects had reached their initial amplitude after 1-3 s. The individual correlation between decay and recovery was negative but weak, which is interpreted as showing that these processes have a tendency to balance each other, but are based partly on different mechanisms. The implications of the present results for diagnosis of disorders of the lower auditory system as well as for the evaluation of the protective role of the stapedius reflex against noise damage are pointed out.
Acoustic Stimulation↗
Fatigability of the stapedius reflex in industrial noise.
Normal hearing subjects were monaurally exposed to 30 min of tape recorded shipyard noise (97 dB (A)) which is characterized by a variable temporal structure. The stapedius muscle activity was continuously recorded in the opposite ear as a change of the ear's acoustic impedance. The reflex function was, in addition, assessed as stimulus-response curves obtained before and, at various times after, exposure. A slight reflex fatigue was observed, together with a parallel shift of the stimulus-response curve (average 4 dB). The recovery was slow and not complete even 10 min after the end of the exposure. The individual variability was large. For 5 of the subjects the exposure was repeated at a later session and the individual degree of fatigue was found to be largely producible. The present results suggest that the stapedius reflex might play a role in the clinical picture of noise induced hearing loss.
Acoustic Impedance Tests↗
Fatigability of the stapedius reflex in industrial noise. A field study.
The depression of the stapedius reflex after a whole workday in industrial noise was studied in 11 normal-hearing employees at a shipbuilding yard. The reflex activity was assessed with simultaneous bilateral recordings of impedance change induced by stimulation with 2 000 and 500 Hz tones. One ear was exposed for approximately 7 hours in the plant, the other one was protected. The dose was measured individually at 89--103 dB(A) equivalent level. Utilization of bilateral recordings together with a unilateral exposure enabled an analysis based on the whole stimulus response curves. The results show that the reflex is depressed on the average 4 dB at 2 000 Hz 10 min after end of workday. By extrapolation the stapedius reflex was estimated to be depressed less than 10 dB at the end of the exposure. Since the stimulus-response curves are shifted in parallel, the contraction during the high-level components of the noise were largely unaffected. No evidence was found for creation of transtympanic pressure differences during noise exposure. It was concluded that the reflex fulfils one necessary condition for influencing the individual pattern of noise damage to the ear, fatigue resistance in the presence of long-term exposure to hazardous noise.
Acoustic Impedance Tests↗
Dynamic properties of the intra-aural reflex in lesions of the lower auditory pathway. An experimental study in rabbits.
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Animals↗
Hearing thresholds in the rabbit. A behavioral and electrophysiological study.
Thresholds of audibility were determined in rabbits with a behavioral 'conditioned suppression' technique and with brain stem evoked response to band-pass (1/3 and 1/1 octave) filtered sine waves. Both techniques yield threshold curves with the same shape, the ABR threshold being 10-20 dB less sensitive. In rabbits with cochlear lesions (noise or kanamycin), hearing losses obtained with the two methods are very similar. It is concluded that the hearing threshold in rabbits can be obtained both electrophysiologically and behaviorally with techniques suitable for experimental auditory research.
Animals↗
Effect of the acoustic reflex on inner ear damage induced by industrial noise.
Shipyard noise is a variable noise which induces permanent threshold shift (PTS) in exposed workers. In humans, the stapedius reflex has been found to be very stable in this type of exposure. Temporary threshold shift (TTS) in the absence of stapedius reflex has been found to extend downwards through the speech-frequencies instead of showing a high frequency dip as when the stapedius reflex is normal. The features of PTS produced by the same type of noise was investigated in rabbits with and without functioning middle ear muscles. The auditory sensitivity was measured by auditory brain stem response (ABR) and by the stapedius reflex response. Middle ear muscle function was blocked by denervation of the stapedius muscle or by general anesthesia. With normal middle ear reflex very little PTS was found. When the muscles were inactivated during the noise exposure the PTS was very extensive and covered the mid frequency range. On the basis of previous findings in humans and the present animal study it is suggested that the features of the stapedius reflex should be considered both in assessment of individual susceptibility and design of optimal acoustic environments.
Animals↗
Audio-vestibular findings in patients with vestibular neuritis.
19 patients with the clinical diagnosis vestibular neuritis, i.e., cases with unilaterally ENG verified abolished or reduced caloric reactions but without symptoms of central nervous involvement or hearing impairment, participated in the study. In addition to ENG examinations and Békésy audiometry all patients were submitted to stapedius reflex tests and auditory brainstem response examinations (ABR) for signs of subclinical auditory nerve engagement. In all but one of the 19 patients the caloric reactions improved; 8 of the 13 patients available for tests after one year recovered completely. The ABR was normal in all cases but the stapedius reflex thresholds were pathologically elevated and remained so in about half of the subjects throughout the observation time; reflex decay was not present in anyone. Cases with pathologically elevated stapedius reflex thresholds showed a tendency to slower recovery of the vestibular function than the group with the normal reflexes. The results were interpreted to indicate lack of eighth nerve or CNS engagement. The possibility that subjects with reflex threshold elevation may constitute a group with constitutional weakness of the audio-vestibular apparatus disposed for vestibular disease is discussed.
Adult↗
Noise effects on the cochlear vasculature in normotensive and spontaneously hypertensive rats.
The cochlear vessels and the distribution of red blood corpuscles were studied in normotensive (N) and spontaneously hypertensive (SH) rats with and without noise exposure. The evaluation was made in a double blind manner. Ten N-rats and ten SH-rats were exposed to noise for 8 weeks and terminated immediately thereafter. The noise consisted of a 2 kHz broad noise band swept from 3 kHz to 30 kHz with a resultant equivalent sound level of 100 dB (lin) 10 h. Seven of 84 vascular parameters differed statistically at the 1% level between N- and SH-rats, and 8 and 10 parameters respectively differed for N- and SH-rats as a result of noise exposure. The observations were interpreted as indicative of a precapillary sphincter constriction in the radiating arterioles of the external wall with an upstream relative stasis and a downstream relative lack of blood, both in N- and SH-rats. In the spiral lamina the observations were interpreted as signs of a decreased blood flow after noise exposure, both in the N- and SH-animals, and most marked in the SH-animals after noise.
Animals↗
Cis-platin ototoxicity in previously noise-exposed guinea pigs.
The ototoxic effect of Cis-platin on guinea pigs was assessed with frequency-specific brainstem audiometry in the frequency range 0.8-20 kHz. The animals had a noise-induced hearing loss in one ear before Cis-platin treatment. The loss of threshold showed a large inter-individual variability, with a rapid increase above a hypothetic threshold dose. In the noise-exposed ear the total loss was larger, but the additional ototoxic effect was smaller than on the non-exposed side. The hearing loss was independent of pigmentation. in conclusion, there is no potentiation between noise-induced hearing loss and Cis-platin. The data support regular audiometric control before and during Cis-platin treatment for easy detection of incipient hearing loss, before the speech frequency range is affected.
Animals↗
Cochlear blood flow in relation to age in normotensive and spontaneously hypertensive rats.
Cochlear blood flow was studied with the microsphere method in young and old normotensive and spontaneously hypertensive rats. The young animals were 3-6 months old and the old ones 18-24 months. The cochlear blood flow in young rats was 1.64 microliter/min/cochlea for the normotensive and 1.51 for the spontaneously hypertensive rats. In the old rats, the cochlear blood flow rates were 1.40 and 1.29 microliter/min/cochlea, respectively. The differences were not significant between the age groups, nor between the normotensive and spontaneously hypertensive rats. However, there was a tendency towards lower cochlear blood flow with increasing age, especially among the spontaneously hypertensive rats. The difference between young normotensive and old spontaneously hypertensive rats was significant (p less than 0.05). The group of old hypertensive rats was also the only one with evident morphological changes in the organ of Corti.
Animals↗