Eardrum displacement following stapedius muscle contraction

The eardrums move when the eyes move: A multisensory effect on the mechanics of hearing

The peripheral hearing system contains several motor mechanisms that allow the brain to modify the auditory transduction process. Movements or tensioning of either the middle ear muscles or the outer hair cells modifies eardrum motion, producing sounds that can be detected by a microphone placed in the ear canal (e.g., as otoacoustic emissions). Here, we report a form of eardrum motion produced by the brain via these systems: oscillations synchronized with and covarying with the direction and amplitude of saccades. These observations suggest that a vision-related process modulates the first stage of hearing. In particular, these eye movement-related eardrum oscillations may help the brain connect sights and sounds despite changes in the spatial relationship between the eyes and the ears.

Interactions between sensory pathways such as the visual and auditory systems are known to occur in the brain, but where they first occur is uncertain. Here, we show a multimodal interaction evident at the eardrum. Ear canal microphone measurements in humans (n = 19 ears in 16 subjects) and monkeys (n = 5 ears in three subjects) performing a saccadic eye movement task to visual targets indicated that the eardrum moves in conjunction with the eye movement. The eardrum motion was oscillatory and began as early as 10 ms before saccade onset in humans or with saccade onset in monkeys. These eardrum movements, which we dub eye movement-related eardrum oscillations (EMREOs), occurred in the absence of a sound stimulus. The amplitude and phase of the EMREOs depended on the direction and horizontal amplitude of the saccade. They lasted throughout the saccade and well into subsequent periods of steady fixation. We discuss the possibility that the mechanisms underlying EMREOs create eye movement-related binaural cues that may aid the brain in evaluating the relationship between visual and auditory stimulus locations as the eyes move.

The effect of auditory stimulation on the tensor tympani in patients following stapedectomy

CONCLUSION

We believe that a tensor tympani reflex, in response to loud sound, is present in a minority of people, although its functional significance with regard to sound transmission is questionable. The absence of startle response in our stapedectomized subjects makes us question whether the tensor component of the startle response is large enough to be identified by manometry.

OBJECTIVES

This study was organized to examine reflex activity to stimulation by loud sound or by startle in the tensor tympani. Although many previous studies have been carried out, results have been contradictory, and methodological flaws have rendered the interpretations questionable.

PATIENTS AND METHODS

Stapedectomized patients were invited to take part in the study. Thirteen patients underwent testing by extratympanic manometry, using a standard tympanometer. Responses were observed during repeated stimuli with loud sound at 500, 1000, 2000 and 4000 Hz to the ipsilateral and contralateral ears, and with an air jet against the closed eye. A control group was also studied for the startle test.

RESULTS

Three clear ipsilateral (23%) and two clear contralateral (14%) responses to auditory stimuli were seen in the 13 patients. We found responses to startle stimuli in none of our study group and eight (42%) of control ears.

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.

The reversed ipsilateral acoustic reflex: clinical features and kinetic analysis

OBJECTIVE

The reversed ipsilateral acoustic reflex (RIAR) has been the subject of few studies in the past literature and the nature of this "reflex" response is not yet completely understood. It can be observed in different diseases, all of which result from inactivity of the stapedial reflex (SR). We aimed to investigate the occurrence of the RIAR in different diseases.

MATERIAL AND METHODS

An extensive clinical investigation of the RIAR was carried out.

RESULTS

The RIAR was found to be present in 100% of ears lacking an effective SR arc. Its amplitude is modulated by the air pressure level in the external ear canal whilst its sign is constantly positive and never reverses.

CONCLUSION

Kinetic analysis of the RIAR suggests the existence of a single underlying phenomenon while the interaction of the RIAR with the SR may explain the complex morphology frequently observed in the normal ipsilateral acoustic reflex.

Volume displacement of the tympanic membrane in the sitting position as a function of middle ear muscle activity. A quantitative microflow method

An open microflow meter system has been worked out for quantitative recording of the volume displacement of the tympanic membrane and its movement direction at stapedius reflex. An acoustically elicited M. stapedius contraction can be recognized by the characteristic response and latency time. The stapedius reflex contraction causes an outward or inward movement of the tympanic membrane. The magnitude of the volume displacement of the tympanic membrane is influenced by the middle ear pressure and in some ears the movement direction of the tympanic membrane changes.