BACKGROUND AND OBJECTIVES: Although the suppressive effect of the medial efferent acoustic reflex is well known, the time course of this effect over prolonged periods has yet to be fully evaluated. We assessed time-dependent change in the suppression of transient evoked otoacoustic emissions (TEOAEs) by the medial efferent acoustic reflex over a relatively long period. SUBJECTS AND METHODS: We measured TEOAEs in the right ear before contralateral acoustic stimulation (CAS), and then measured serial TEOAEs in the right ear at four intervals during a total of 16 minutes of continuous CAS, followed by three more recordings after termination of CAS. RESULTS: TEOAE amplitudes were reduced with CAS during a certain period (from the immediate period to 10 minutes depending on frequency) and subsequently recovered. TEOAE suppression values in the mean amplitudes for overall frequency were 0.76 dB at the initial recording, 0.35 dB at 5 minutes, 0.44 dB at 10 minutes, and 0.33 dB at 15 minutes during CAS. The initial suppression value was significantly larger than other suppression values of 5, 10, and 15 minutes (p<0.05). In recordings obtained after CAS, TEOAE amplitude exceeded pre-acoustic amplitudes at 1 kHz, 1.5 kHz, and 2 kHz. CONCLUSIONS: The present results show the existence of the medial efferent acoustic reflex and demonstrate the time course that TEOAE suppressions present initially after CAS, showing fatigue over time. Overshooting of TEOAE was observed in recordings at several frequencies after termination of CAS.
Acoustic Stimulation ; Acoustics ; Ear ; Fatigue ; Reflex, Acoustic

BACKGROUND AND OBJECTIVES: Although the suppressive effect of the medial efferent acoustic reflex is well known, the time course of this effect over prolonged periods has yet to be fully evaluated. We assessed time-dependent change in the suppression of transient evoked otoacoustic emissions (TEOAEs) by the medial efferent acoustic reflex over a relatively long period. SUBJECTS AND METHODS: We measured TEOAEs in the right ear before contralateral acoustic stimulation (CAS), and then measured serial TEOAEs in the right ear at four intervals during a total of 16 minutes of continuous CAS, followed by three more recordings after termination of CAS. RESULTS: TEOAE amplitudes were reduced with CAS during a certain period (from the immediate period to 10 minutes depending on frequency) and subsequently recovered. TEOAE suppression values in the mean amplitudes for overall frequency were 0.76 dB at the initial recording, 0.35 dB at 5 minutes, 0.44 dB at 10 minutes, and 0.33 dB at 15 minutes during CAS. The initial suppression value was significantly larger than other suppression values of 5, 10, and 15 minutes (p<0.05). In recordings obtained after CAS, TEOAE amplitude exceeded pre-acoustic amplitudes at 1 kHz, 1.5 kHz, and 2 kHz. CONCLUSIONS: The present results show the existence of the medial efferent acoustic reflex and demonstrate the time course that TEOAE suppressions present initially after CAS, showing fatigue over time. Overshooting of TEOAE was observed in recordings at several frequencies after termination of CAS.
Acoustic Stimulation ; Acoustics ; Ear ; Fatigue ; Reflex, Acoustic

BACKGROUND AND OBJECTIVES: There are several methods for lowering the acoustic reflex hreshold, a process known as "facilitaion". The most popular facilitation method is the simultaneous stimulation of a high-frequency tone (facilitator) with a reflex-elicing tone (activator). This study was performed in order to analyze and generalize the facilitation phenomenon, and infer clinical applications from this phenomenon. MATERIALS AND METHODS: Authors measured the acoustic reflex thresholds when the facilitators of various amplitudes and frequencies was simultaneously stimulated in normal population. Also, the effects of facilitation was observed on the growth function curve (a curve showing the acoustic reflex pattern in subthreshold and suprathreshold stimulation). RESULTS: Facilitation was observed more effectively by using facilitators of high frequencies and high amplitudes. In the analysis of growth function curve, we found similar result as above. But there was no correlation between the frequency of activator and the mode of facilitation. CONCLUSION: We analyzed the factors affecting the phneomenon of facilitation and discussed a several proposals explaining the different tendencies of facilitation. Further studies should be made on the clinical implication of this phenomenon to sensorineurally hearing-impaired patients or children.
Acoustics* ; Child ; Humans ; Reflex, Acoustic*

BACKGROUND AND OBJECTIVES: Stapedial reflex (SR) threshold is of considerable diagnostic significance in the evaluation of audiological function, especially under sedation or general anesthesia since anesthetic drugs often act on neurotransmitters or neuromodulators. The aim of this study was to evaluate the changes in the SR threshold according to the depth of anesthesia. SUBJECTS AND METHOD: Sixty patients with normal hearing who were scheduled for operation under general anesthesia were included in this study. Anesthetic agent used was propofol and the depth of anesthesia was monitored by the bispectral index (BIS). SR was measured five times according to depth of anesthesia. RESULTS: Both ipsilateral and contralateral SR thresholds were increased according to the depth of anesthesia using propofol. In particular, ipsilateral SR showed no response at BIS 60 and contralateral SR at BIS 40. However, there were no significant differences between age groups and gender. CONCLUSION: Propofol significantly increased both ipsilateral and contralateral SR threshold according to depth of anesthesia. When it is necessary to measure SR under general anesthesia, we should consider the effect on SR threshold according to the depth of anesthesia.
Anesthesia ; Anesthesia, General ; Anesthetics ; Cellulose ; Hearing ; Humans ; Neurotransmitter Agents ; Propofol ; Reflex ; Reflex, Acoustic

Mass and stiffness affect on the peculiar characteristics of transmission of the middle ear and the distinctive behavior of the cochlear mechanics. Applying the principle of the mass and stiffness, the band-pass characteristic transfer function of the middle ear has been explained. The greatest transfer function of the middle ear, approximately 24-29 dB, is observed at 1-2 kHz in both cat and human species. However, at lower frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear cavity. At higher frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear bones. Several examples, such as an acoustic reflex, otitis media, and otosclerosis are discussed. For understanding the traveling wave of the basilar membrane, different place tuning at certain stimulus frequencies, contrastingly shaped basilar membrane to the cochlear duct, and the structural and physical characteristics of the whole cochlear partition were reviewed in terms of changing width, mass, and stiffness from the base to apex. Being about ten times wider, more massive, and one hundredfold stiffer at the base than the apex, the nature of the cochlear partition to absorb high-frequency energy changes in fluid pressure declines toward the apex. Consequently, at the base of the cochlea, high frequencies stimuli are decoded while low frequencies stimuli are decoded at the apex of the cochlea. Due to these characteristics of the cochlear partition, the direction of the traveling wave was also proved to be in the fashion of base-to-apex always.
Animals ; Basilar Membrane ; Cats ; Cochlea ; Cochlear Duct ; Ear, Middle* ; Humans ; Mechanics ; Otitis Media ; Otosclerosis ; Reflex, Acoustic

BACKGROUND AND OBJECTIVES: Click sound can evoke myogenic potentials in active sternocleidomastoid(SCM) muscle. These potentials are due to the activity of the vestibular rather than cochlear afferents, which produce very short latency inhibition of ipsilateral motor unit activity and is best detected by averaging the unrectified surface electromyogram(EMG) from the muscle. We investigated the click evoked vestibulocollic reflexes in neck muscles to find out the significance and relationship of latency and amplitude of myogenic potentials between two different methods of muscle activation. METHODS: EMGs were recorded from surface electrode evoked by sound stimuli (95dB, 5/sec repetitive rate, 512 times) over SCM muscles on each side. Myogenic potential have two biphasic responses, which are termed P1, N1, P2 and N2 based on the polarity of their components. The subjects were 24 normal volunteers. Surface EMG activities from 12 subjects(Group I) were recorded by neck flexion to activate bilateral SCM muscles through the averaging runs(bilateral SCM muscle activation method). EMGs from another 12 subjects(Group II) were recorded by rotating head to the opposite side to activate SCM muscle throughout the procedure(unilateral SCM muscle activation method). The latencies and amplitudes of myogenic potential in the SCM muscle after stimulation were analysed and compared between each method. RESULTS: The latencies(msec) of P1 and N1 were 11.2+2.4, 21.7+1.1 in Group 1, respectively and 13.3+2.4, 23.0+/-1.1 in Group 11, respectively. The amplitudes(microvolt) of P1-N1 were 38.7+8.1 in Group 1 and 33.2+8.1 in Group II. There was no significant difference in latencies and amplitudes of P1 and N1 between each group(p> 0.05) and was no asymmetry of latency and amplitude in P1-N1 between each side. CONCLUSIONS: The myogenic potential was constantly evoked by click stimulation and we think it could be a simple method of examining vestibulocollic reflex.
Acoustic Stimulation* ; Electrodes ; Head ; Healthy Volunteers ; Muscles ; Neck ; Neck Muscles ; Reflex*

Tinnitus is a common auditory phenomenon associated with many otological diseases, and is usually subjective. Objective tinnitus can be generated by para-auditory structures, usually derived from vascular or myogenic sources, or the eustachian tube. We present a rare case of intermittent unilateral tinnitus associated with eye blinking. Otoendoscopic examination showed that the external auditory canals and tympanic membranes were normal; however, rhythmic movements of both tympanic membranes, concomitant with the tinnitus, were evident whenever the patient blinked. The tympanometry and stapedial reflexes measured via impedance audiometry exhibited saw-tooth patterns; movement of the tympanic membrane was associated with eyelid blinking. The patient was managed conservatively, with reassurance and medication, and the condition became well-controlled. Here, we present this educational case and review the literature.
Acoustic Impedance Tests ; Blinking* ; Ear Canal ; Ear Diseases ; Eustachian Tube ; Eyelids ; Humans ; Reflex ; Tinnitus* ; Tympanic Membrane

OBJECTIVES: Baso-apical gradients exist in various cochlear structures including medial olivocochlear (MOC) efferent system. This study investigated the cochlear regional differentials in the function and morphology of the MOC system, and addressed the functional implications of regional MOC efferent terminals (ETs) in the mouse cochlea. METHODS: In CBA/J mice, MOC reflex (MOCR) was assessed based on the distortion product otoacoustic emission in the absence and presence of contralateral acoustic stimulation. High, middle, and low frequencies were grouped according to a mouse place-frequency map. Cochlear whole mounts were immunostained for ETs with anti-α-synuclein and examined using confocal laser scanning microscopy. The diameters of ETs and the number of ETs per outer hair cell were measured from the z-stack images of the basal, middle and apical regions, respectively. RESULTS: The middle cochlear region expressed large, clustered MOC ETs with strong MOCR, the base expressed small, less clustered ETs with strong MOCR, and the apex expressed large, but less clustered ETs with weak MOCR. CONCLUSION: The mouse cochlea demonstrated regional differentials in the function and morphology of the MOC system. Strong MOCR along with superior MOC morphology in the middle region may contribute to ‘signal detection in noise,’ the primary efferent function, in the best hearing frequencies. Strong MOCR in spite of inferior MOC morphology in the base may reflect the importance of ‘protection from noise trauma’ in the high frequencies.
Acoustic Stimulation ; Animals ; Cochlea* ; Hair ; Hearing ; Mice* ; Microscopy, Confocal ; Noise ; Reflex

BACKGROUND AND OBJECTIVES: Vestibular evoked myogenic potential (VEMP) is muscle reflex caused by surface electrodes following repeated high-intensity auditory stimulation. The current study attempted to determine whether VEMP can be consistently evoked from the sternocleidomastoid muscle (SCM) by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst. SUBJECTS AND METHOD: Air-conducted and bone-conducted VEMPs in response to 500 Hz-tone burst were recorded from the SCM of 13 normal volunteers. Subjects were seated on their chairs and made to hold their heads turned up as far as possible towards the side, contralateral to the stimulated ear voluntarily. Two different sound durations (rise/fall time=2 msec, plateau time=2 msec[2/2] and rise/fall time=5 msec, plateau time=5 msec[5/5]) were presented through a insertphone or bone vibrators. Latencies and amplitudes of p13 and n23 responses were measured. RESULTS: All normal volunteers showed p13-n23 responses to 50 dB bone-conducted tone burst as well as to 100 dB air-conducted tone burst. The values of latency of p13 and n23 were the most reliable at 5/5 air-conducted in evaluation by coefficiency of variance. Mean p13 and N23 latencies by airconducted tone burst were significantly longer than those of bone-conducted. Mean p13-n23 amplitudes by air-conducted tone burst were significantly larger than those by bone-conducted at 2/2 sound duration. CONCLUSION: VEMP could be consis-tently evoked by the 100 dB air-conducted and 50 dB bone-conducted 500 Hz-tone burst, especially at 5/5 air-conducted.
Acoustic Stimulation ; Ear ; Electrodes ; Head ; Healthy Volunteers ; Reflex ; Vestibular Evoked Myogenic Potentials*

Dehiscence of bone overlying the superior semicircular canal (superior semicircular canal dehiscence syndrome) may have both vestibular and auditory manifestations. Lowered vestibular evoked myogenic potential (VEMP) threshold in patients with an apparent conductive hearing loss and normal acoustic reflex also suggests this syndrome. Herein, we present a patient with the Tullio phenomenon, sound induced nystagmus, vibration induced nystagmus, and lowered VEMP threshold without conductive hearing loss due to the superior semicircular canal dehiscence.
Evoked Potentials ; Hearing Loss, Conductive ; Humans ; Reflex, Acoustic ; Semicircular Canals* ; Vertigo ; Vibration