Haim Sohmer

Hebrew University of Jerusalem, Yerushalayim, Jerusalem, Israel

Are you Haim Sohmer?

Claim your profile

Publications (233)255.12 Total impact

  • Ronen Perez · Cahtia Adelman · Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: Conclusion Cochlea can be directly excited by fluid (soft-tissue) stimulation. Objective To determine whether there is no difference in auditory-nerve-brainstem evoked response (ABR) thresholds to fluid stimulation between normal and animal models of post radical-mastoidectomy, as seen in a previous human study. Background It has been shown in humans that hearing can be elicited with stimulation to fluid in the external auditory meatus (EAM), and radical-mastoidectomy cavity. These groups differed in age, initial hearing, and drilling exposure. To overcome this difference, experiments were conducted in sand-rats, first intact, and after inducing a radical-mastoidectomy. Methods The EAM of five sand-rats was filled with 0.3 ml saline. ABR thresholds were determined in response to vibratory stimulation by a clinical bone-vibrator with a plastic rod, applied to the saline in the EAM. Then the tympanic membrane was removed, and malleus dislocated (radical-mastoidectomy model). The cavity was filled with 0.45 ml saline and the ABR threshold was determined in response to vibratory stimulation to the cavity fluid. Results There was no difference in ABR fluid thresholds to EAM and mastoidectomy cavity stimulation. Air-conduction stimulation from the bone-vibrator was not involved (conductive loss due to fluid). Bone-conduction stimulation was not involved (large difference in acoustic impedance between fluid and bone).
    No preview · Article · Jan 2016 · Acta oto-laryngologica
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The mechanism of human hearing under water is debated. Some suggest it is by air conduction (AC), others by bone conduction (BC), and others by a combination of AC and BC. A clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax also elicits hearing by a mechanism called soft tissue conduction (STC) or nonosseous BC. The present study was designed to test whether underwater hearing at low intensities is by AC or by osseous BC based on bone vibrations or by nonosseous BC (STC). Thresholds of normal hearing participants to bone vibrator stimulation with their forehead in air were recorded and again when forehead and bone vibrator were under water. A vibrometer detected vibrations of a dry human skull in all similar conditions (in air and under water) but not when water was the intermediary between the sound source and the skull forehead. Therefore, the intensities required to induce vibrations of the dry skull in water were significantly higher than the underwater hearing thresholds of the participants, under conditions when hearing by AC and osseous BC is not likely. The results support the hypothesis that hearing under water at low sound intensities may be attributed to nonosseous BC (STC).
    Full-text · Article · Dec 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: Osseous bone conduction (BC) stimulation involves applying the clinical bone vibrator with an application force of about 5 Newton (N) to the skin over the cranial vault of skull bone (e.g., mastoid, forehead). In nonosseous BC (also called soft tissue conduction), the bone vibrator elicits hearing when it is applied to skin sites not over the cranial vault of skull bone, such as the neck. To gain insight into the mechanisms of osseous and nonosseous BC. In general, thresholds were determined with the bone vibrator applied with about 5 N force directly to osseous sites (mastoid, forehead) on the head of the participants, as classically conducted in the clinic, and again without direct physical contact (i.e., 0 N force) achieved by coupling the bone vibrator to gel as in ultrasound diagnostic imaging, on the same or nearby skin sites (nonosseous BC). The participants were equipped with earplugs to minimize air-conducted stimulation. In the first experiment, 10 normal-hearing participants were tested with stimulation (5 and 0 N) at the forehead; in the second experiment, 10 additional normal-hearing participants were tested with stimulation at the mastoid (about 5 N) and at the nearby tragus and cavum concha of the external ear (0 N). The mean thresholds with 0 N were much better than might be expected from classical theories in response to stimulation by a bone vibrator, in the absence of any application force. The differences between the mean thresholds with the 0 N and the 5 N forces depended on condition, site, and stimulus frequency of the comparisons. The difference was 1.5 dB at 1.0 kHz on the forehead; ranged between 10 and 12.5 dB at 1.0 kHz on the cavum and tragus (versus on the mastoid) and at 2.0 and 4.0 kHz on the forehead; 17 and 19 dB at 2.0 kHz on the cavum and tragus (versus on the mastoid); reaching 32 dB only in a single condition (forehead at 0.5 kHz). As it is unlikely that threshold intensity stimulation delivered with 0 N application force could have induced vibrations of the underlying or nearby bone, inducing osseous BC, the relatively low thresholds in the absence of any application force, together with the small differences between the thresholds with 0 N (gel/soft tissue, nonosseous) and 5 N force (osseous BC) lead to the suggestion that in most situations, the BC thresholds actually represent the nonosseous (soft tissue conduction) thresholds at the stimulation site. American Academy of Audiology.
    No preview · Article · Jul 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Hearing is elicited by applying the clinical bone vibrator to soft tissue sites on the head, neck, and thorax. Two mapping experiments were conducted in normal hearing subjects differing in body build: determination of the lowest soft tissue stimulation site at which a 60 dB SL tone at 2.0 kHz was effective in eliciting auditory sensation and assessment of actual thresholds along the midline of the head, neck, and back. In males, a lower site for hearing on the back was strongly correlated with a leaner body build. A correlation was not found in females. In both groups, thresholds on the head were lower, and they were higher on the back, with a transition along the neck. This relation between the soft tissue stimulation site and hearing sensation is likely due to the different distribution of soft tissues in various parts of the body.
    Full-text · Article · May 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to differentiate between a conductive hearing loss (CHL) and a sensorineural hearing loss (SNHL) in the hearing-impaired individual, we compared thresholds to air conduction (AC) and bone conduction (BC) auditory stimulation. The presence of a gap between these thresholds (an air-bone gap) is taken as a sign of a CHL, whereas similar threshold elevations reflect an SNHL. This is based on the assumption that BC stimulation directly excites the inner ear, bypassing the middle ear. However, several of the classic mechanisms of BC stimulation such as ossicular chain inertia and the occlusion effect involve middle ear structures. An additional mode of auditory stimulation, called soft tissue conduction (STC; also called nonosseous BC) has been demonstrated, in which the clinical bone vibrator elicits hearing when it is applied to soft tissue sites on the head, neck, and thorax. The purpose of this study was to assess the relative contributions of threshold determinations to stimulation by STC, in addition to AC and osseous BC, to the differential diagnosis between a CHL and an SNHL. Baseline auditory thresholds were determined in normal participants to AC (supra-aural earphones), BC (B71 bone vibrator at the mastoid, with 5 N application force), and STC (B71 bone vibrator) to the submental area and to the submandibular triangle with 5 N application force) stimulation in response to 0.5, 1.0, 2.0, and 4.0 kHz tones. A CHL was then simulated in the participants by means of an ear plug. Separately, an SNHL was simulated in these participants with 30 dB effective masking. STUDY SAMPLE consisted of 10 normal-hearing participants (4 males; 6 females, aged 20-30 yr). AC, BC, and STC thresholds were determined in the initial normal state and in the presence of each of the simulations. The earplug-induced CHL simulation led to a mean AC threshold elevation of 21-37 dB (depending on frequency), but not of BC and STC thresholds. The masking-induced SNHL led to a mean elevation of AC, BC, and STC thresholds (23-36 dB, depending on frequency). In each type of simulation, the BC threshold shift was similar to that of the STC threshold shift. These results, which show a similar threshold shift for STC and for BC as a result of these simulations, together with additional clinical and laboratory findings, provide evidence that BC thresholds likely represent the threshold of the nonosseous BC (STC) component of multicomponent BC at the BC stimulation site, and thereby succeed in clinical practice to contribute to the differential diagnosis. This also provides evidence that STC (nonosseous BC) stimulation at low intensities probably does not involve components of the middle ear, represents true cochlear function, and therefore can also contribute to a differential diagnosis (e.g., in situations where the clinical bone vibrator cannot be applied to the mastoid or forehead with a 5 N force, such as in severe skull fracture). American Academy of Audiology.
    No preview · Article · Jan 2015 · Journal of the American Academy of Audiology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Soft tissue conduction (STC) is a recently expounded mode of auditory stimulation in which the clinical bone vibrator delivers auditory frequency vibratory stimuli to skin sites on the head, neck, and thorax. Investigation of the mechanism of STC stimulation has served as a platform for the elucidation of the mechanics of cochlear activation, in general, and to a better understanding of several perplexing auditory phenomena. This review demonstrates that it is likely that the cochlear hair cells can be directly activated at low sound intensities by the fluid pressures initiated in the cochlea; that the fetus in utero, completely enveloped in amniotic fluid, hears by STC; that a speaker hears his/her own voice by air conduction and by STC; and that pulsatile tinnitus is likely due to pulsatile turbulent blood flow producing fluid pressures that reach the cochlea through the soft tissues.
    No preview · Article · Sep 2014 · Journal of basic and clinical physiology and pharmacology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Active middle ear implants such as the vibrant sound bridge (VSB) have been placed on the round window (RW) in patients with conductive or mixed hearing loss, with satisfactory hearing results. Several observations show that the mechanism of RW stimulation is not completely understood. The purpose of the present study was to compare different coupling procedures between the transducer and the RW in order to contribute to an understanding of the mechanism of RW stimulation. Methods: Five fat sand rats underwent ablation of the left ear and opening of the right bulla, followed by baseline measurements of thresholds of auditory nerve brainstem evoked responses (ABR) to air and bone conduction click stimuli. Subsequently the malleus and incus were removed from the right middle ear, modeling a conductive hearing loss in which the VSB on the RW is indicated. In the next stage of the experiment, a rod attached to the bone vibrator was placed gently on the RW membrane and then on saline fluid applied to the RW niche. ABR thresholds were recorded following both placements. Results: Mean baseline ABR threshold in response to air conduction stimuli was 48 ± 4 dB; mean ABR threshold when the rod was placed on the dry RW membrane was 99 ± 12 dB; mean ABR threshold when the rod was in the saline on RW niche was 79 ± 7 dB. Conclusions: ABR thresholds were better (lower) with stimulation of fluid on the RW membrane compared to direct stimulation of the RW, providing further evidence of a direct fluid pathway.
    No preview · Article · Jul 2014 · Journal of basic and clinical physiology and pharmacology
  • Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: Air conduction (AC) is accompanied by displacements of the two cochlear windows, bulk fluid flow between them, a pressure difference across the basilar membrane, leading to a passive traveling wave along the membrane, which activates the cochlear amplifier and enhances the displacements. AC interacts with bone conduction (BC) stimulation, so that it has been assumed that BC stimulation also involves a passive traveling wave. However, several clinical conditions and experimental manipulations provide evidence that a passive traveling wave may not be involved in BC stimulation at low intensities. Soft tissue conduction (STC) (also called non-osseous bone conduction) involves applying the bone vibrator to soft tissues on the head, neck and thorax, eliciting auditory sensation. STC stimulation probably does not involve a passive traveling wave. This review presents clinical conditions and experimental manipulations which assess the contributions of AC, BC and STC stimulation to the passive traveling wave. Evidence from the clinic (otosclerosis, round window atresia) and from the laboratory (holes in the wall of the inner ear, immobilization of the ossicular chain and the windows, discontinuity of the chain, measurement of basilar membrane displacements in the absence of the cochlear amplifier) lead to the conclusion that a passive basilar membrane traveling wave may not be involved in stimulation at low sound intensities. It is suggested that at low sound levels, the outer hair cell cochlear amplifier may not be activated by a passive traveling wave, but may be directly activated by the fast cochlear fluid pressures induced by AC, BC and STC stimulation. On the other hand, at high intensities, the cochlea is activated by the slow passive traveling wave.
    No preview · Article · Apr 2014 · Archives of Oto-Rhino-Laryngology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Clinical conditions have been described in which one of the two cochlear windows is immobile (otosclerosis) or absent (round window atresia), but nevertheless bone conduction (BC) thresholds are relatively unaffected. To clarify this apparent paradox, experimental manipulations which would severely impede several of the classical osseous mechanisms of BC were induced in fat sand rats, including discontinuity or immobilization of the ossicular chain, coupled with window fixation. Effects of these manipulations were assessed by recording auditory nerve brainstem evoked response (ABR) thresholds to stimulation by air conduction (AC), by osseous BC and by non-osseous BC (also called soft tissue conduction-STC) in which the BC bone vibrator is applied to skin sites. Following the immobilization, discontinuity and window fixation, auditory stimulation was also delivered to cerebro-spinal fluid (CSF) and to saline applied to the middle ear cavity. While the manipulations (immobilization, discontinuity, window fixation) led to an elevation of AC thresholds, nevertheless, there was no change in osseous and non-osseous BC thresholds. On the other hand, ABR could be elicited in response to fluid pressure stimulation to CSF and middle ear saline, even in the presence of the severe restriction of ossicular chain and window mobility. The results of these experiments in which osseous and non-osseous BC thresholds remained unchanged in the presence of severe restriction of the classical middle ear mechanisms and in the absence of an efficient release window, while ABR could be recorded in response to fluid pressure auditory stimulation to fluid sites, indicate that it is possible that the inner ear may be activated at low sound intensities by fast fluid pressure stimulation. At higher sound intensities, a slower passive basilar membrane traveling wave may serve to excite the inner ear.
    No preview · Article · Jan 2014 · Archives of Oto-Rhino-Laryngology
  • Cahtia Adelman · Haim Sohmer · Ronen Perez
    [Show abstract] [Hide abstract]
    ABSTRACT: Background: Soft tissue conduction (STC) is a recently described mode of auditory stimulation in which vibrations induced by a clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax of human subjects reach the cochlea and elicit auditory sensation. In humans, STC stimulation interacts with air conduction stimulation and with bone conduction (BC) stimulation in several ways, e.g., mutual masking. Methods: This study investigated whether mutual masking between STC and BC stimulation can be demonstrated in an experimental animal. In fat sand rats, auditory nerve and brainstem evoked response to BC stimulation was recorded in the presence of noise masking presented by STC and vice versa. Results: STC successfully masked BC, and BC also masked STC responses. Conclusions: Mutual masking, now demonstrated in animals, paves the way for animal experiments to clarify the pathway between the STC stimulation sites and the cochlea.
    No preview · Article · Aug 2013
  • Cahtia Adelman · Ronen Perez · Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: Auditory sensation can be elicited by applying a bone conduction vibrator to skin sites on the head, neck, and thorax over soft tissues. This is called soft tissue conduction (STC). We hypothesized that introducing substances with acoustic impedances that sharply deviate from those of soft tissues, such as air pockets, into the soft tissues beneath soft tissue stimulation sites would have an effect on the auditory threshold to stimulation at skin sites over soft tissue. In human subjects, we assessed the auditory threshold with a bone vibrator applied to several STC sites, especially the cheek, and to several bone conduction sites on the skull. The subjects were equipped with bilateral earplugs. The subject then filled his or her cheek with either air or water, and the auditory threshold was again determined. We also recorded the auditory brain stem response to STC stimulation under the chin in fat sand rats in the absence and presence of subcutaneous air or saline solution pockets (0.4 mL) under the chin. In humans, the threshold to stimulation on the cheek was elevated (13 to 18 dB) in the presence of an air-inflated cheek, but not with a water-filled cheek. In animals, in the presence of an air pocket, the auditory brain stem response threshold was elevated by 10 to 20 dB; no threshold change occurred with a saline solution pocket. The introduction of air (but not water) into the soft tissues beneath the soft tissue stimulation sites led to a threshold elevation in both humans and animals. This was not the case when an identical volume of water was introduced, which would also have interrupted a possible parallel bone conduction pathway. These results provide evidence that soft tissue stimulation at low intensities induces tissue vibrations that are transmitted to the cochlea along a series of soft tissues with similar acoustic impedances.
    No preview · Article · Aug 2013 · The Annals of otology, rhinology, and laryngology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Soft tissue conduction (STC), a recently described mode of auditory stimulation elicited when the clinical bone vibrator is applied to skin sites over the head, neck, and thorax, complements air conduction (AC) and bone conduction (BC), elicited by the same vibrator. The study assessed skull bone vibrations induced during STC and BC stimulation. Methods: The experiments were conducted on fat sand rats. Thresholds of auditory nerve brainstem evoked responses (ABRs) were recorded and compared to the lowest-intensity sound stimuli that elicited vibrations at the bony vestibule of the inner ear detected by a laser Doppler vibrometer. Results: Vibrations were detected during BC but not during STC stimulation. ABR was recorded to both STC and to BC stimulation. Conclusions: Low-intensity STC stimulation does not induce vibrations of the inner ear, showing that STC apparently does not involve mechanisms based on vibrations of bone.
    No preview · Article · Jul 2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: To assess and compare the effect of commonly used topical antimycotic agents and their solvents on the function of the vestibular and cochlear parts of the sand rat's inner ear. Prospective, controlled, animal study. Forty-five fat sand rats were randomly assigned to five major groups, each receiving topical application of a different agent: saline (control), gentamicin (ototoxic control), and three antimycotic agents: nystatin, clotrimazole solution (Agisten), and bifonazole solution (Agispor). All animals underwent a right labyrinthectomy, and a polyethylene tube was inserted into the left middle ear followed by baseline recording of vestibular evoked potentials (VsEPs) and auditory nerve and brainstem responses (ABR). Subsequently, each animal received five consecutive daily applications of the specific agent into the left middle ear. Evoked potential recordings were repeated 3 and 10 days after the last application and compared to baseline. For clotrimazole and bifonazole solutions, the effect of the solvents was assessed by comparing ABR recordings at similar intervals. Administration of saline did not affect VsEPs or ABR. Both could not be recorded following gentamicin application. In all three antimycotic agents, no statistically significant difference was found between VsEPs recordings before and after application. Clotrimazole and bifonazole solutions caused a significant ABR threshold elevation similar to that caused by their solvents. Nystatin caused a less significant ABR threshold elevation. The three commonly used topical antimycotic agents investigated here did not affect vestibular function but had a toxic effect on inner ear cochlear function. It seems the main offenders were the solvents.
    No preview · Article · Apr 2013 · The Laryngoscope
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Auditory sensation can be elicited not only by air conduction (AC) with an earphone and by bone conduction by applying a bone vibrator to bony sites on the head, but also by a newly described mode based on applying the bone vibrator to soft tissue sites on the head, neck, and thorax (soft tissue conduction - STC). This study was designed to assess whether it is necessary to compress the skin at the STC sites, which could induce vibrations of the underlying bone. Methods: In 15 normal-hearing subjects, thresholds were assessed with the bone vibrator in air (control for possible AC), direct contact of the bone vibrator with the mastoid and regions around the lip, and indirect contact (via a cotton wool wick, dry or wet) of the bone vibrator with sites around the lip. Results: Even though the best (lowest) thresholds were obtained with direct contact, the subjects clearly heard the sound stimulation when presented only by the gentle contact of the wick with the skin, especially when the contact site was moist. Conclusions: STC stimulation does not require vibrations of the skull bone and seems to involve the transmission of auditory frequency vibrations, through a series of soft tissues, to the inner ear.
    No preview · Article · Oct 2012 · Journal of basic and clinical physiology and pharmacology
  • Cahtia Adelman · Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: This study was designed to compare the thresholds to a standard clinical bone vibrator applied to sites on the head over skull bone (bone conduction, BC) and to soft tissue sites on the head and neck (soft tissue conduction, STC) with static application forces of 100 and 500 g in order to assess the possibility that STC is actually a form of BC, since both are elicited by stimulation with the same bone vibrator. Thresholds to 2.0-kHz tones were assessed in dB hearing level settings of the audiometer in the BC stimulation mode. There was no difference in threshold between forces of 100 and 500 g when applied to the skull bone sites (e.g. mastoid, forehead). However, at soft tissue sites (e.g. below the ear lobe, under the chin, on the sterno-cleido-mastoid muscle), thresholds to 100 g were significantly higher (poorer) than those to 500 g. With the 500 g static force (and also with the 100 g force), the thresholds at the STC sites were higher (poorer) than those at the skull bone sites. These findings have implications for understanding BC and STC modes of auditory activation.
    No preview · Article · Oct 2012 · Audiology and Neurotology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Auditory sensation can be elicited by air conduction (AC) and by bone conduction (BC). It is also possible to elicit such responses by applying the standard clinical bone vibrator to the skin over soft tissue sites on the head, neck, or thorax of humans and animals. This mode of auditory stimulation has been called soft tissue conduction (STC). This study was designed to investigate the pathway between soft tissue sites and the ear. The air in the middle ear was replaced with saline solution in an animal with unique anatomy--the fat sand rat, in which about 70% of a thin-walled inner ear bulges into the middle ear bulla cavity--while we recorded the auditory brain stem responses (ABRs) to AC, BC, and STC stimulation. This replacement of air with saline solution led to a significant improvement in STC threshold. With AC stimulation, the ABR threshold was elevated and the latency of the first ABR wave was prolonged. Consistent changes were not seen with BC stimulation. When the air (which has a very low acoustic impedance) that normally surrounds most of the inner ear is replaced with saline solution (which has an acoustic impedance similar to that of soft tissues), the STC threshold is improved. This improvement may be due to improved transmission of acoustic energy from the soft tissues to the inner ear.
    No preview · Article · Sep 2012 · The Annals of otology, rhinology, and laryngology
  • Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: The hair cells are the receptor cells of the inner ear. There is still controversy concerning the mechanism of their activation. Studies on the hair cells of the bullfrog sacculus have provided much information on the activity of hair cells. However, the mammalian cochlea has two different types of hair cells - the inner hair cells (IHCs) and the outer hair cells (OHCs) - and it is likely that their activation mechanisms are not identical. Mechanical manipulations of the cochlea and measurements of the passive and active displacements of the basilar membrane in the normal and postmortem cochleas provide evidence that the OHCs are activated directly by the fluid pressures induced in the cochlea by low-level sound, and not indirectly by a passive traveling wave. The activated OHCs produce active displacements (the cochlear amplifier) which excite the IHCs, probably by deflecting their stereocilia, followed by excitation of the auditory nerve fibers.
    No preview · Article · Mar 2012 · Journal of basic and clinical physiology and pharmacology
  • Michal Kaufmann · Cahtia Adelman · Haim Sohmer
    [Show abstract] [Hide abstract]
    ABSTRACT: This study was designed to map the sites on the skin of the head, neck and thorax at which a clinical bone vibrator elicits auditory sensation. In 10 subjects with normal hearing, a bone vibrator delivering a 2000-Hz warble tone, at an intensity which was at least 5 dB below the intensity which elicited a sensation by air conduction over each site, was applied to 25 sites with an application force of 500 g. Auditory sensations were elicited at many soft tissue (underlying bone >1 cm below the skin) and osseous (bone <0.5 cm below the skin) sites on the head, neck and thorax in all subjects, down to the sternum and thoracic vertebrae. Therefore, auditory vibrations induced at many sites on the head, neck and thorax can reach the cochlea and elicit auditory sensation.
    No preview · Article · Feb 2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: Auditory sensation can be elicited not only by air conducted (AC) sound or bone conducted (BC) sound, but also by stimulation of soft tissue (STC) sites on the head and neck relatively distant from deeply underlying bone. Tone stimulation by paired combinations of AC with BC (mastoid) and/or with soft tissue conduction produce the same pitch sensation, mutual masking and beats. The present study was designed to determine whether they can also cancel each other. The study was conducted on ten normal hearing subjects. Tones at 2 kHz were presented in paired combinations by AC (insert earphone), by BC (bone vibrator) at the mastoid, and by the same bone vibrator to several STC sites; e.g. the neck, the sterno-cleido-mastoid muscle, the eye, and under the chin, shifting the phases between the pairs. Subjects reported changes in loudness and cancellation. The phase for cancellation differed across subjects. Neck muscle manipulations (changes in head position) led to alterations in the phase at which cancellation was reported. Cancellation was also achieved between pairs of tones to two STC sites. The differing phases for cancellation across subjects and the change in phase accompanying different head positions may be due to the different acoustic impedances of the several tissues in the head and neck. A major component of auditory stimulation by STC may not induce actual skull bone vibrations and may not involve bulk fluid volume displacements.
    No preview · Article · Jan 2012 · Hearing research
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A major cause of the hearing loss following exposure to intense noise involves release of free radicals resulting from the elevated metabolism. The free radicals induce damage to several of the components of the cochlear amplifier including the outer hair cells and indirectly to the transduction currents. Salicylic acid induces a reversible hearing loss since it binds to the motor protein prestin in the outer hair cells, reducing electromotility. Furosemide also induces a reversible hearing loss since it reduces the endocochlear potential which is a major component of the cochlear transduction currents. On the other hand, each of these drugs also provides protection from a noise induced hearing loss if they are injected just before a noise exposure, probably as a result of the decreased metabolism induced in their presence, with release of lower levels of free radicals. In this study, both drugs were administered in order to assess whether their protective effects would be additive. The study was conducted on normal hearing albino mice of the Sabra strain. They were injected with either salicylic acid alone (N = 11), or furosemide alone (N = 14), or both together (N = 14), or with saline control (N = 11) and exposed to broad band noise for 3.5 hours. An additional group of 9 mice was injected with both salicylic acid and furosemide, but not exposed to noise. The degree of the resulting hearing loss was assessed by recording thresholds of the auditory nerve brainstem evoked responses to broad band clicks before the injections and noise, and 7, 14 and 21 days after. The noise induced hearing loss in the mice injected with salicylic acid alone or furosemide alone was smaller than in those injected with saline, i.e. these drugs provided protection, as in previous studies in this laboratory. There was no threshold elevation after two weeks in the mice injected with both drugs without noise exposure, i.e. the effects of the two drugs given together was reversible. On the other hand, there was a significant hearing loss (i.e. threshold elevation) in the group which received both drugs and was also exposed to noise, with mean threshold elevations of 38.8 ± 19.0 dB and 28.3 ± 11.7 dB 7 days after noise exposure. This result is very surprising, if not paradoxical. Drugs which provide protection from a noise induced hearing loss when administered alone, not only do not provide protection when given together, but also induce a greater hearing loss when accompanied by noise. This observation may be related to the finding that the depression of the endocochlear potential normally caused by furosemide is reduced in the presence of salicylic acid, so that the protection usually provided by furosemide is not present when it is administered together with salicylic acid. Thus it seems that each drug may interfere with the protective action of the other when coupled with noise.
    Full-text · Article · Jan 2012 · Journal of Occupational Medicine and Toxicology

Publication Stats

4k Citations
255.12 Total Impact Points

Institutions

  • 1965-2015
    • Hebrew University of Jerusalem
      • • Department of Medical Neurobiology
      • • Department of Physiology
      Yerushalayim, Jerusalem, Israel
  • 2011
    • Hadassah Academic College
      Yerushalayim, Jerusalem, Israel
  • 2000-2003
    • Shaare Zedek Medical Center
      • Department of Otolaryngology and Head and Neck Surgery
      Yerushalayim, Jerusalem, Israel
  • 1984
    • Sapienza University of Rome
      Roma, Latium, Italy
  • 1978
    • Tel Aviv University
      Tell Afif, Tel Aviv, Israel
  • 1977
    • Hadassah Medical Center
      • Department of Physiology
      Yerushalayim, Jerusalem District, Israel