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PubMed2000

Modeling mode arrivals in the 1995 SWARM experiment acoustic transmissions

As part of the Shallow Water Acoustics in a Random Medium (SWARM) experiment, a 16 element WHOI vertical line array (WVLA) was moored in 70 m of water off the New Jersey coast. A 400-Hz acoustic tomography source was moored some 32-km shoreward of this array, such that an acoustic path was created that was anti-parallel to the primary propagation direction for shelf-generated internal wave solitons. The presence of these soliton internal waves in the acoustic waveguide causes significant coupling of energy between propagating acoustic modes, creating fluctuations in modal intensities and modal peak arrival times, as well as time spreading of the pulses. Two methods by which acoustic propagation and scattering in soliton-filled waveguides can be modeled are presented here in order to understand and explain the scattering observed in the SWARM field data. The first method utilizes the Preisig and Duda [IEEE J. Ocean. Eng. 22, 256-269 (1997)] Sudden Interface Approximation (SIA) to represent the solitons. The second method, which is computationally slower, uses a finely meshed, "propagated" thermistor record to simulate the solitons in the SWARM experiment waveguide. Both numerical methods are found to generate scattering characteristics that are similar to the SWARM field data.

Journal Article↗
PubMed2000

Three-dimensional acoustic scattering from a penetrable layered cylindrical obstacle in a horizontally stratified ocean waveguide

In this work, a normal-mode solution is presented for the three-dimensional problem of acoustic scattering from a penetrable horizontally layered cylindrical obstacle in a shallow-water waveguide. The ocean environment around the obstacle is considered horizontally stratified and the bottom is assumed to be rigid. In the general case of depth-dependent sound-speed and density profiles (ssdp) the total acoustic field is calculated numerically, while an analytic solution is obtained in the special case of depth-independent ssdp. Numerical results concerning the transmission loss outside and inside single or double-layered cylindrical structures made of acoustic materials are given for a typical depth-dependent ocean environment. Comparisons with the cases of ideally soft and ideally hard cylindrical obstacles [J. Acoust. Soc. Am. 100, 206-218 (1996)] are also made, illustrating the effect of acoustic properties of the obstacle. An important feature, which clearly emerges from the theoretical analysis and the numerical results, is the necessity of including evanescent modes in the calculations, in order to obtain physically meaningful and numerically accurate results. Furthermore, analytical expressions for the scattering cross section of a (penetrable or impenetrable) cylindrical obstacle are derived in terms of the expansion coefficients of the pressure field, and their behavior as frequency increases is numerically investigated. The solution presented in this paper, although addressing a special geometry, provides a means for handling strong discontinuities in both vertical and horizontal directions, and can serve as a benchmark solution to a problem for which no general numerical model exists, i.e., modeling acoustic scattering from a 3D obstacle in a 3D shallow-water waveguide.

Journal Article↗
PubMed2000

Effects of race and sex on acoustic features of voice analysis.

This study sought to provide preliminary normative data for the vocal productions of 44 Euro-American and 40 African-American elderly speakers and to test the hypotheses that (1) Euro-American elderly speakers do not have significantly different acoustic parameters of voice from African-American elderly speakers, and (2) elderly male speakers (both Euro-American and African-American) do not have significantly different acoustic parameters of voice from elderly female speakers (both Euro-American and African-American). Voice samples from groups of 44 Euro-American (21 men and 23 women) and 40 African-American (20 men and 20 women) elderly speakers (ages 70 to 80 years) from northeastern Arkansas were compared on measures of 15 selected multidimensional voice profile (KAY Elemetrics) acoustic parameters. Analysis show that Euro-American elderly speakers did not differ significantly from African-American elderly speakers on the measurements of all the selected acoustic parameters of voice, and elderly male speakers as a group differed from elderly female speakers on the measurements of absolute jitter, soft phonation index, and standard deviation of the fundamental frequency as well as fundamental frequency in Hz. The findings suggest it may not be necessary to establish separate acoustic norms of voice for Euro-American and African-American elderly speakers. However, some acoustic parameters of voice are highly sex-dependent, and different norms may be needed for male and female speakers regardless of their racial origins.

Black or African American↗
PubMed1992

The acoustic cortex in Alzheimer's disease.

The morphology of the acoustic cortex was studied in light and electron microscopy, in 6 post mortem cases of Alzheimer's disease. Silver impregnation techniques and routine stainings were applied for the study of the cytoarchitecture and the cellular morphology of the acoustic cortex. Samples from every part of the acoustic cortex were processed for electron microscopy. The morphological findings were correlated with those of normal controls of relevant age, as well as with the temporal isocortex of the anterior part of the superior temporal gyrus. Silver impregnation techniques revealed a marked loss of dendritic spines in the second, third and fourth cortical layers. An obvious decrease of the axonic collaterals of the large triangular and round neurons was also seen. Neurofibrillary tangles were found in the soma and the initial part of the axon in a large number of neurons, being more prominent in the neurons of the second and third cortical layers. Senile plaques were dispersed all over the acoustic cortex. Electron microscopy revealed numerous paired helical filaments (PHF) located mostly in the soma and the axons of the large neurons as well as numerous Hirano bodies. Synaptic alterations, such as polymorphism of the synaptic vesicles in the presynaptic terminals, dilatation of the synaptic cleft and accumulation of osmiophilic material in the postsynaptic terminals were seen in numerous synaptic profiles in the acoustic cortex. The rare dendritic spines developed synaptic contact practically only with one presynaptic terminal, in contrast to the normal controls which demonstrated numerous dendritic spines developing synapses with more than one presynaptic terminal. The morphological alterations in the acoustic cortex might explain the profound deficit in verbal memory and the language disturbances that are hallmarks in early cases of Alzheimer's disease.

Alzheimer Disease↗
PubMed1994

Acoustic neuroma presented as repeated hearing loss.

Up to 15% of patients with acoustic neuroma may have a history of sudden hearing loss. Recovery from sudden hearing loss with acoustic neuroma is rare. In this paper, a case of bilateral acoustic neuromas presented as repeated sudden hearing loss with recovery on the left side after removal of right-sided tumor were reported. She experienced three episodes of sudden hearing loss, showing various types of audiograms and ABR on the left side. There was no relationship between the type of audiograms and ABR findings. Factor influencing ABR might be different from the cause of hearing impairment. Acoustic neuromas can be reliably identified by performing MRI properly. However, MRI showed negative scan and ABR finding was abnormal in the first episode of our case. ABR continues to be a sensitive diagnostic back-up test to MRI for the detection of acoustic neuromas. Even if the patient, who showed abnormal ABR findings suggesting retrocochlear pathology, showed normal MRI, acoustic neurinoma should not be ruled out and both ABR and MRI must be re-examined at regular intervals.

Adult↗
PubMed1998

[Evaluation of nasal obstruction with acoustic rhinometry: a simulated study with a nasal model].

The measurement of nasal resistance is important for understanding the pathophysiology of nasal obstruction. However, it is difficult to define the normal range of nasal resistance because of various physiological factors. Several authors have reported that nasal resistance is not correlated with the sensation of nasal obstruction. On the other hand, acoustic rhinometry was introduced by Hilberg et. al. (1989) to determine the geometry of the nasal cavity. The method based on sound reflection analysis provides an estimate of the cross-sectinal area of the nasal cavity as a function of the distance from the nostril. Recently, the measurement by acoustic rhinometry is becoming popular also in our country. However, the assessment by acoustic rhinometry may be different from that by measuring nasal resistance because the cross-sectional area is measured without studying the air flow. The aim of this study was to investigate the benefit of acoustic rhinometry using a nasal model. First, 4 pieces of nasal model LM005 (KOKEN, Co., Japan) made of silicone were coated with resinous putty. Then, the changes in the area-distance curve were measured with an acoustic rhinometer RHIN 2100 (SRE, Co., Denmark) in which this putty was scraped off gradually from anterior to posterior. In the next study, the quality of coated putty was increased at three points of the nasal area: anterior part, middle part, and posterior part. Thereafter the changes in the area-distance curve were observed in the same way. As a result, neither a decrease or an increase in the putty changed the area-distance curve at the posterior part. Therefore, it is suitable that the degree of the changing of nasal mucosa is defined as the change in the nasal volume between the top the I-notch and the end of the C-notch. In conclusion, acoustic rhinometry is useful to investigate nasal obstruction, especially the change in the nasal mucosa. Therefore, further clinical study is required for the different purpose of measuring nasal resistance.

Airway Resistance↗
PubMed1999

Acoustic-phonetic approach toward understanding neural processes and speech perception.

This review paper describes an "acoustic-phonetic" experimental approach aimed at understanding normal and abnormal speech perception processes from both a behavioral and an electrophysiologic perspective. First, we consider the relevant acoustic characteristics of speech and identify a set of acoustic-phonetic classes that represent the parameters most important for making an acoustic signal sound like speech. Second, we review what is known about the neurophysiologic representation of acoustic-phonetic speech parameters in animal and human subjects. Third, we describe how an acoustic-phonetic approach has been useful in understanding the biologic basis of some auditory learning problems in children and in characterizing the behavioral and neurophysiologic changes resulting from speech-sound training. Finally, we discuss these findings and how they may expand the diagnostic and rehabilitative repertoire of practicing audiologists.

Auditory Cortex↗
PubMed2001

Correlation of acoustic velocity of synovial fluid with markers of inflammation in arthritic patients.

Analysis of synovial fluid is important in the evaluation and treatment of arthritic conditions. This study measured the acoustic velocity of synovial fluids in patients with degenerative joint diseases, crystal arthropathy, and other inflammatory arthropathies using the ultrasonic pulse-echo method. The measured acoustic velocities of these bio-fluids were then correlated with clinical parameters including the synovial white blood cell count (WBC), clarity, viscosity, string test, erythrocyte sedimentation rate (ESR), and serum C-reactive protein (CRP). Results showed that the acoustic velocities were correlated with ESR (p = 0.0016) and CRP (p = 0.0001). The mean acoustic velocity of inflammatory synovial fluids, defined as synovial fluids with WBCs of more than 2000/mm3, was greater than that of synovial fluids with WBCs of less than 2000/mm3 (1550 +/- 4.5 m/s vs 1544 +/- 1.5 m/s, p = 0.007). This study demonstrated that the acoustic velocity of synovial fluid correlates well with severity of inflammation. These findings suggest that measurement of acoustic velocity may be useful in the clinical evaluation and management of arthritic conditions.

Arthritis↗
PubMed2002

Rapid growth of acoustic neuromas after stereotactic radiotherapy in type 2 neurofibromatosis.

We describe a rare complication of stereotactic radiotherapy for large acoustic neuromas in a patient with type 2 neurofibromatosis. We retrospectively reviewed the case of a 14-year-old girl who had been referred to our tertiary care center. Prior to referral, the patient had been evaluated for hoarseness. During the work-up, magnetic resonance imaging (MRI) detected two large bilateral acoustic neuromas and two bilateral jugular foramen tumors. The patient was diagnosed with type 2 neurofibromatosis, and she underwent stereotactic radiotherapy for treatment of the two acoustic neuromas; the jugular foramen tumors were not irradiated. The patient's post-treatment course was complicated by hydrocephalus and symptoms of brainstem compression, which required urgent surgical intervention. Follow-up MRI 7 months following radiotherapy demonstrated a rapid growth of the acoustic neuromas, but no appreciable change in the size of the jugular foramen neuromas. These findings suggest that the radiotherapy might have been the cause of the rapid growth of the acoustic neuromas. To our knowledge, no such report has been published in the literature, and this phenomenon might be unique. Our findings suggest that radiotherapy might not be the optimal first-line treatment for acoustic neuromas in patients with type 2 neurofibromatosis.

Adolescent↗
PubMed1999

[Bilateral acoustic neuromas].

OBJECTIVE: To investigate the clinical course, growth character and treatment of bilateral acoustic neuromas (BANs). METHODS: Five cases of BANs were reported. RESULTS: From 1986 to 1996, 92 patients with acoustic tumors were managed. Of them, 5(5%) bilateral acoustic neuromas were observed. All patients were males, the age at the time of testing ranged from 16 to 31 years (mean 23.8 years). In all patients, progressive hearing loss and tinnitus were the most common initial symptoms. In addition, signs of other cranial nerve deficits were detected in all patients. Two cases had cafe au lait spots and all cases had neurofibromas of varying sizes and shapes in subcutaneous tissues. Four had unilateral acoustic tumors operated on, one by the translabyrinthine approach, 3 by the suboccipital approach. One patient died due to encephaledema and hernia of brain after operation. According to the MRI data in one case, the average growth rate of acoustic tumor was 1.1 cm (superior/inferior) and 0.7 cm (medical/lateral) per year. CONCLUSION: The management of BANs patients presents challenging problems different from the unilateral acoustic tumors.

Adolescent↗
PubMed1992

Mid-infrared pulsed laser ablation of the arterial wall. Mechanical origin of "acoustic" wall damage and its effect on wall healing.

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall, 184 craters (1 mm diameter and 1 mm depth) were produced perpendicular to the intimal lining in the thoracic aortas of pigs. Three types of craters were evaluated: Ho-YSGG laser-induced (lambda = 2.09 microns, 2 pulses of 500 microseconds, 0.50 joule/pulse, 50 gm force), mechanically drilled, and "acoustic" craters. "Acoustic" craters were produced by two laser pulses delivered into a saline-filled metal fiber cap, which was placed in a mechanically drilled crater. The metal cap was provided with four outlets for water vapor and isolated "acoustic" from optical and thermal laser effects. The pigs survived 3, 14, and 28 days. Arterial wall damage, medial necrosis, and wall healing were assessed microscopically. At 3 days, laser and "acoustic" craters were accompanied by large tissue ruptures (2.7 +/- 0.9 mm and 2.9 +/- 0.8 mm, respectively, mean +/- standard deviation). These were attributed to large vapor bubbles expanding within the tissue. A zone of medial necrosis was observed adjacent to the laser craters (0.43 +/- 0.15 mm) and to the "acoustic" craters (0.17 +/- 0.14 mm). Neither ruptures nor necrosis was observed with the mechanical craters. At 2 and 4 weeks, the necrotic areas were repopulated with smooth muscle cells and all craters were adequately filled with smooth muscle cells, without any sign of an exaggerated proliferative response. We conclude that within the arterial wall, Ho-YSGG ablation was accompanied by the rapid expansion of a water vapor bubble. The formation of the relatively large vapor bubble is inherent to the use of a mid-infrared laser. The risk of creating dissections clinically, when delivering Ho-YSGG laser pulses, remains to be determined. The present study provided no indication that the arterial wall fissures might affect the restenosis rate unfavorably by promoting myointimal proliferation.

Angioplasty, Laser↗
PubMed2004

Differentiation between benign and malignant hepatic lesions: utility of color stimulated acoustic emission with the microbubble contrast agent Levovist.

OBJECTIVE: This study was undertaken to determine whether the examination of color stimulated acoustic emission in the late phase of Levovist (SH U 508A; Schering AG, Berlin, Germany) enhancement is helpful in the discrimination between benign and malignant liver lesions. METHODS: Fifty-six patients with focal hepatic lesions were examined. Diagnosis of the lesions was confirmed by liver biopsy, computed tomography, or scintigraphy. Thirty-one patients had malignant liver lesions: hepatocellular carcinoma (n = 14), cholangiocellular carcinoma (n = 1), metastasis (n = 14), and lymphoma (n = 2). Twenty-five patients had benign lesions: focal nodular hyperplasia (n = 8), hepatic adenoma (n = 1), focal hyposteatosis or hypersteatosis (n = 6), hemangioma (n = 7), and regenerative cirrhotic nodules (n = 3). After a delay of 5 to 10 minutes without scanning, the liver was examined by color stimulated acoustic emission with a fast sweep of 1 to 3 seconds. RESULTS: All patients with homogeneous color stimulated acoustic emission in the late phase of Levovist enhancement had benign liver lesions (P < .001; specificity, 100%; sensitivity, 68%; positive predictive value, 100%; and negative predictive value, 79%). Eighty-one percent of the patients with nonenhancing lesions in the late phase surrounded by enhanced liver parenchyma had malignant liver lesions (P < .001; specificity, 72%; sensitivity, 94%; positive predictive value, 81%; and negative predictive value, 90%). Interobserver agreement (weighted kappa value) improved from 0.570 +/- 0.038 for baseline sonography to 0.918 +/- 0.028 for color stimulated acoustic emission sonography. The area under the receiver operating characteristic curves for color stimulated acoustic emission sonography (0.927) was significantly higher than for baseline sonography (0.739; P < .05). CONCLUSIONS: Color stimulated acoustic emission in the late phase of Levovist enhancement has a high specificity and sensitivity for differentiation between benign and malignant focal liver lesions.

Analysis of Variance↗
PubMed1992

[Acoustic rhinometry: the bat principle of the nose].

All cross-sectional areas of the upper airway can be measured by an acoustic signal using the acoustic reflection technique, or acoustic rhinometry. The plane of the cross-sectional areas measured was determined in nasal models. The isotemporal layers were found to be nearly parallel to the nasal valve. The acoustically measured cross-sectional areas correlated with the cross-sectional areas of cuts from nasal models. After digitizing these cuts, a CAD software calculates cross-sectional areas in all orientations and at all distances. The difference between the measured and calculated cross-sectional areas is up to 3% in the nasal cavity and up to 17% in the nasopharynx. The hypothesis that the cross-sectional areas measured lie nearly parallel to the nasal valve was confirmed. The normal rhinometric curve shows the minimal cross-sectional area (I-notch) to lie at the nasal isthmus. The second narrowest segment of the nasal cavity lies at the head of the inferior concha and septal concha (C-notch). Characteristic examples of patients with turbinate hypertrophy, choanal atresia, enlarged adenoids, and septal deviations are presented. Acoustic rhinometric curves can only be interpreted in combination with the rhinoscopic findings because different pathological conditions can produce similar curves. Recording of reliable and reproducible data by acoustic rhinometry demands that the connection between the rhinometer and the nose does not distort the valve area. When we used two different nose pieces (1.2 and 1.5 cm outer diameter) the cross-sectional areas in the anterior third of the nose of only 28% of the patients was measured correctly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoids↗
PubMed2004

[Premature ventricular contraction during myocardial contrast echocardiography: relationship with imaging method, acoustic power and dose of contrast agent].

OBJECTIVES: This study investigated the influence of imaging method, acoustic power, and dose of contrast agent on the occurrence of premature ventricular contraction during myocardial contrast echocardiography. METHODS: Myocardial contrast echocardiography was performed with a Toshiba POWER VISION 6000 and YM454 (Definity in USA) contrast agent. Myocardial contrast echocardiography in the short-axis view at the mid-papillary muscle level and electrocardiography in lead II were recorded on videotape in nine awake beagles. The imaging method was continuous, using 1:1 and 1:4 intermittent end-systolic triggered mode. Acoustic power was low, middle and high (as mechanical index, 0.4, 0.8 and 1.0 at continuous mode and 0.6, 1.0 and 1.4 at intermittent mode). YM454 was given intravenously at doses of 1, 10, 30, 50 and 100 microliters/kg/min. Premature ventricular contractions were counted on the videotape for each experimental condition. The examination was repeated on a separate day to ascertain the reproducibility. RESULTS: At low and middle acoustic power, no premature ventricular contraction was induced with any combinations of YM454 doses and trigger intervals. The highest incidence of premature ventricular contraction was 5.1% of all ultrasound pulses at the combination of high acoustic power, 1:4 intermittent and 30 microliters/kg/min of YM454. All premature ventricular contractions induced by trigger mode were observed concomitantly to the end-systolic phase. Reproducibility was low at 0.9%. CONCLUSIONS: Although high acoustic power, intermittent myocardial contrast echocardiography with high dose of contrast agent induced premature ventricular contractions, the incidence of premature ventricular contractions was low. Low acoustic power or low dose of contrast agent induced no premature ventricular contractions.

Animals↗
PubMedDate not supplied

Acoustic properties of articular cartilage under mechanical stress.

Mechano-acoustic and elastographic techniques may provide quantitative means for the in vivo diagnostics of articular cartilage. These techniques assume that sound speed does not change during tissue loading. As articular cartilage shows volumetric changes during compression, acoustic properties of cartilage may change affecting the validity of mechano-acoustic measurements. In this study, we examined the ultrasound propagation through human, bovine and porcine articular cartilage during stress-relaxation in unconfined compression. The time of flight (TOF) technique with known cartilage thickness (true sound speed) as well as in situ calibration method [Suh, Youn, Fu, J. Biomech. 34 (2001), 1347-1353] were used for the determination of sound speed. Ultrasound speed and attenuation decreased in articular cartilage during ramp compression, but returned towards the level of original values during relaxation. Variations in ultrasound speed induced an error in strain and compressive moduli provided that constant ultrasound speed and time-of-flight data was used to determine the tissue thickness. Highest errors in strain (-11.8 +/- 12.0%) and dynamic modulus (15.4 +/- 17.9%) were recorded in bovine cartilage. TOF and in situ calibration methods yielded different results for changes in sound speed during compression. We speculate that the variations in acoustic properties in loaded cartilage are related to rearrangement of the interstitial matrix, especially to that of collagen fibers. In human cartilage the changes, are, however relatively small and, according to the numerical simulations, mechano-acoustic techniques that assume constant acoustic properties for the cartilage will not be significantly impaired by this phenomenon.

Adult↗
PubMed1994

Vocal-acoustic pathways in a teleost fish.

Many teleost fish generate acoustic signals for vocal communication by the synchronized, high-frequency contraction of skeletal, sonic muscles. In midshipman, eight groups of brainstem neurons were distinguished after biocytin application to the sonic nerve that, we propose, represent the entire vocal motor circuit. Biocytin-filled terminals were ubiquitous within all areas containing labeled neurons and, together with ultrastructural evidence, suggested a serial, transneuronal transport at synaptic sites between at least three neuronal groups. The most intensely labeled neurons were positioned in the caudal brainstem and included a previously characterized pacemaker-motoneuron circuit and a newly recognized ventral medullary nucleus that itself gave rise to extensive commissural and lateral brainstem bundles linking the pacemaker circuitry to the rostral brainstem. Five additional groups formed a column rostrally within the medial brainstem adjacent to eighth nerve (octaval)-recipient nuclei largely presumed to be acoustic. This column extended dorsally up to the ventricular cell layer and as far anterior as midbrain isthmal levels. The best-defined group was in the octaval efferent nucleus that directly innervates the sacculus that is considered the auditory division of the inner ear. Saccular afferents and neurons throughout the medial column were also filled after biocytin application to the saccular nerve. This vocal-acoustic network overlaps low-threshold, electrical stimulation sites in the rostral brainstem that elicit vocalizations. The medial column must therefore be the origin of the descending pathway controlling activation of the vocal pacemaker circuitry and likely forms the basis for acoustically elicited vocalizations. We suggest this network, together with input from the pacemaker circuitry, is also the origin of a vocal-related, corollary discharge to acoustic nuclei. Direct links between vocal and acoustic brain regions are thus traits common to aquatic and terrestrial vertebrates.

Animals↗
PubMed1993

Electrical resonance of isolated hair cells does not account for acoustic tuning in the free-standing region of the alligator lizard's cochlea.

The cochlea of the alligator lizard is divided into two morphologically and physiologically distinct regions. In the "tectorial region," hair bundles of hair cells are draped by a tectorial membrane, whereas in the "free-standing region," hair bundles are said to be free-standing because there are no overlying tectorial structures. The acoustic tuning of the free-standing region depends at least in part on mechanical resonances of the hair bundles. In the turtle cochlea, in contrast, acoustic tuning depends in large part upon the electrical properties of the hair cells. We have investigated the electrical properties of hair cells isolated from the free-standing region of the alligator lizard's cochlea. When injected with steps of depolarizing current, these "free-standing hair cells" exhibited electrical resonances that were comparable in frequency and quality to electrical resonances in cochlear hair cells from turtles, chicks, and alligators, and in saccular hair cells from frogs and fish. In the lizard's free-standing hair cells, however, the electrical resonance frequencies (< 300 Hz) were a decade below the cells' acoustic characteristic frequencies (between 1 and 4 kHz), showing that the electrical resonance is not likely to contribute to acoustic tuning. The electrical resonances were not apparent at rest. The cells' resting potentials were significantly more negative than the activation voltage (approximately -40 mV) of the Ca(2+)-dependent K+ current upon which the electrical resonance has been shown to depend in other hair cells. At potentials more negative than -50 mV, an inwardly rectifying K+ conductance dominated. Because we observed no electrical tuning above 300 Hz, our results indirectly support a mechanical origin for acoustic tuning in the free-standing region of the alligator lizard cochlea. These results further show that acoustic tuning cannot be inferred solely from the electrical resonances of isolated hair cells.

Animals↗
PubMed1979

Otolithic-acoustic interaction in the control of eye movement.

In order to examine otolithic contribution to eye movements ten subjects were asked to track either a moving acoustic target or a stationary target during subject linear motion on a cart. The relative displacement between the subject and the target was the same in the two situations. Recordings of eye movements during subject lateral acceleration in the dark without any task, or with the task of tracking an imagined stationary target were made as a control. The frequencies ranged between 0.15 and 0.3 Hz and peak acceleration between 0.55 and 1.2 m/s2. No lateral eye movements (L-nystagmus) were recorded in the dark. Only saccadic eye movements were recorded during the tracking of a moving acoustic target. Slow eye movements interspersed by saccades were observed when the moving subject tracked an imagined or an acoustic stationary target. Contribution of the slow phase to tracking was more important in the presence of an acoustic target than in the presence of imagined target. The results are interpreted in terms of an otolithic contribution to the central reconstruction of the acoustic target velocity, or in terms of an adaptive control of the otolithic-ocular reflex gain. A conceptual model accounting for these interpretations is proposed.

Acoustic Maculae↗