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At least 109 records · Page 6Linked to original sources
PubMed1985

Fetal acoustic stimulation testing: a retrospective experience with the fetal acoustic stimulation test.

The nonstress test is of accepted value in the surveillance of high-risk pregnancies. In order to improve the efficiency of testing, the authors retrospectively evaluated the adjunctive use of acoustic stimulation testing (FAS-TEST) in 1241 patients who underwent 3464 antepartum fetal heart rate tests. The results were compared to those in the previous 6 months during which time 1307 patients underwent 3573 nonstress tests. The frequency of nonreactive tests was 12.6% in the nonstress test group and 6.1% in those patients who underwent the FAS-TEST. The antepartum fetal death rates were not significantly different when the two groups were compared. The FAS-TEST decreases the percentage of nonreactive tests in a high-risk population and, as a consequence, may reduce the testing time.

Acoustic Stimulation↗
PubMed1990

Non-contact acoustic method for the simultaneous measurement of thickness and acoustic properties of biological tissues.

The frequency dependence of the magnitude and phase shift of reflected waves from a thin tissue specimen has been found to yield characteristic patterns as a function of the specimen thickness. By analysis of those characteristic patterns, the specimen thickness can be determined so that the attenuation constant and the sound speed can be obtained by a non-contact procedure. The method is demonstrated in the frequency range 100 MHz to 200 MHz, using a scanning acoustic microscope and approximately 10 microns thick myocardial tissue samples of human origin, one paraffin embedded.

Acoustics↗
PubMed1995

Acoustic features and acoustic changes are represented by different central pathways.

The central processing of acoustic stimulus changes can be observed neurophysiologically in the mismatch negativity auditory evoked potential (MMN). Stimuli differing in interaural phase were used to investigate the contributions of the primary and non-primary auditory pathways to the encoding of binaural stimuli and to investigate passively elicited measures of binaural processing in experimental animals. In guinea pigs, the MMN was obtained in response to 1000 Hz tones embedded in white noise (S:N = 2 dB). Using a modified oddball paradigm (that is, two stimuli presented in a series, each with a different probability of occurrence), stimuli were presented binaurally with both the tone and noise in-phase to the two ears (S0N0) as the standard stimulus ans the tone 180 degrees out-of-phase (S(PI)N0) as the deviant stimulus. The MMN, by definition, should occur only in response to a change, or 'mismatch,' between the standard and deviant stimuli. The response to the deviant stimulus in the oddball paradigm was compared to the response to the same stimulus when presented in a series alone. The responses to S0N0 and S(PI)N0 collected in a series alone, termed the intrinsic responses, were also compared. Responses were recorded from two surface epidural electrodes - one at the posterior midline and one over the left temporal lobe. AEPs from these locations have been shown to reflect the activity of primary and non-primary thalamo-cortical pathways respectively. A significant MMN was observed at the midline electrode, but no MMN was observed over the temporal lobe.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed2005

External inferior colliculus integrates trigeminal and acoustic information: unit responses to trigeminal nucleus and acoustic stimulation in the guinea pig.

The external nucleus of the inferior colliculus (ICx) receives ascending projections from both auditory and somatosensory nuclei. In the guinea pig, both the spinal trigeminal nucleus (TN) and the cochlear nucleus converge in the ventrolateral region of ICx. We investigated the function of trigeminal-collicular pathways by electrically stimulating the TN while recording unit responses from ICx. Pairing electrical stimulation with acoustic stimuli allowed us to investigate the function of converging auditory and somatosensory inputs, i.e. multisensory integration. Unit responses were recorded from ICx using a multi channel, single shank electrode. Electrical stimulation of the TN produced small changes above or below spontaneous rate, but resulted in significant suppression or enhancement of sound-evoked responses. Multisensory integration has been demonstrated in the dorsal cochlear nucleus (DCN), superior colliculus and sensory cortices and may play a role in plasticity that occurs after sensory deprivation.

Acoustic Stimulation↗
PubMed2002

Acoustic inhomogeneity of carotid arterial plaques determined by GHz frequency range acoustic microscopy.

Characterization of the structure and composition of carotid arterial plaques is important to predict the risk of embolic and thrombotic events. In clinical echography, echolucent lesions seem to be more associated with stroke than echogenic lesions, and a low grey-scale median is associated with a fivefold increase in the incidence of silent infarcts. In the present study, five fixed human carotid atherosclerotic lesions were observed by GHz-range scanning acoustic microscopy (SAM). The atherosclerotic lesions were characterized by either thickened fibrosis with dense collagen fibers or lipid accumulation with sparse collagen network by optical microscopy. SAM revealed that the fibrosis was classified into type I and III collagen by attenuation of ultrasound (US) and that the sound field of lipid accumulation lesions became inhomogeneous. The results would provide the scientific basis for the images of vulnerable plaques being produced in diagnostic US.

Acoustics↗
PubMed2002

Provisional mapping of quantitative trait loci modulating the acoustic startle response and prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) of the acoustic startle response (ASR) is a form of sensorimotor gating, defined as an inhibition of the startle response when a low intensity stimulus, the prepulse, precedes the startling stimulus. Deficits in PPI have been reported in schizophrenia and other psychiatric/neurological disorders, and correlate with symptom severity in schizophrenia, suggesting that deficient PPI per se or abnormalities in neural circuits regulating PPI may cause some symptoms of schizophrenia. If so, then genes conferring reduced PPI may contribute toward genetic vulnerability to schizophrenia. Studies with selectively bred rodent strains indicate that PPI is under genetic control; however, the identity of the relevant genes is unknown. The current study used recombinant congenic mouse strains derived from C57BL/6J and A/J parents to assess genetic variability in PPI and in ASR and to identify provisional quantitative trait loci (QTLs) modulating these phenotypes. Significant between-strain differences in ASR and in PPI at each of several prepulse intensities (75, 80, 85, 90, 95 dB) were found. Correlations between PPI at the various prepulse intensities were highly significant, suggesting appreciable overlap in genetic regulation of PPI across prepulse intensities. Five QTLs (chromosomes 3, 5, 7, 16) associated with PPI across all prepulse intensities, but not with ASR, were identified. Two additional QTLs (chromosomes 2, 11) associated with both PPI and ASR were found. Fifteen QTLs were associated with ASR alone. Data on genotypes of informative congenic strains were used to support probable involvement of loci modulating PPI and to narrow the probable chromosomal location of QTLs. If confirmed, these QTLs may suggest candidate genes directing novel mechanisms for regulation of PPI

Acoustic Stimulation↗
PubMed2003

Similar effects of attention directed to acoustic and tactile stimuli on prepulse inhibition of acoustic startle.

Prepulse inhibition (PPI) is assumed to index automatic and controlled processing. In three experiments (n= 32, 22, and 30) participants were asked to judge the duration of a prepulse in comparison with a stimulus presented 4000 ms before the prepulse. A distracter was presented simultaneously with the prepulse to increase the cognitive demands of the task. PPI was assessed at stimulus onset asynchronies (SOAs) of 30-150 ms, and 420 ms. The prepulse was either a tone (60 dB) or a tactile stimulus (21 kPa), and startle was elicited by 95 dB white noise. Directing attention to the prepulse increased PPI at SOAs of 60 ms and longer in all experiments, but the sensory modality to which attention was directed played only a minor role. We conclude that directing attention to both acoustic and tactile prepulses increased PPI.

Acoustic Stimulation↗
PubMed2002

Acoustic competition in the gulf toadfish Opsanus beta: acoustic tagging.

Nesting male gulf toadfish Opsanus beta produce a boatwhistle advertisement call used in male-male competition and to attract females and an agonistic grunt call. The grunt is a short-duration pulsatile call, and the boatwhistle is a complex call typically consisting of zero to three introductory grunts, a long tonal boop note, and zero to three shorter boops. The beginning of the boop note is also gruntlike. Anomalous boatwhistles contain a short-duration grunt embedded in the tonal portion of the boop or between an introductory grunt and the boop. Embedded grunts have sound-pressure levels and frequency spectra that correspond with those of recognized neighbors, suggesting that one fish is grunting during another's call, a phenomenon here termed acoustic tagging. Snaps of nearby pistol shrimp may also be tagged, and chains of tags involving more than two fish occur. The stimulus to tag is a relatively intense sound with a rapid rise time, and tags are generally produced within 100 ms of a trigger stimulus. Time between the trigger and the tag decreases with increased trigger amplitude. Tagging is distinct from increased calling in response to natural calls or stimulatory playbacks since calls rarely overlap other calls or playbacks. Tagging is not generally reciprocal between fish, suggesting parallels to dominance displays.

Acoustics↗
PubMed2003

Acoustic tumors: operation versus radiation--making sense of opposing viewpoints. Part II. Acoustic neuromas: sorting out management options.

Patients with acoustic neuromas have several options available to them. Large tumors with significant brain stem compression usually require surgical resection. For patients with small or medium-sized tumors, radiosurgery has become a common treatment, with excellent long-term results being reported. Patients must be comfortable with the concept of tumor control rather than tumor removal. Most seem to be satisfied with this concept if it allows them to avoid brain surgery. Surgeons should strive to educate their patients with information from the peer-reviewed literature. Confusion exists among patients, because the information from Internet sources, newsletters, support groups, and physicians has not always been validated and supported by outcomes data. Although we are asked to provide our opinions, our comments should not be based on myth, conjecture, training bias, or socioeconomic concerns.

Decision Making↗
PubMed2003

Numerical investigation and electro-acoustic modeling of measurement methods for the in-duct acoustical source parameters.

It is known that the direct method yields different results from the indirect (or load) method in measuring the in-duct acoustic source parameters of fluid machines. The load method usually comes up with a negative source resistance, although a fairly accurate prediction of radiated noise can be obtained from any method. This study is focused on the effect of the time-varying nature of fluid machines on the output results of two typical measurement methods. For this purpose, a simplified fluid machine consisting of a reservoir, a valve, and an exhaust pipe is considered as representing a typical periodic, time-varying system and the measurement situations are simulated by using the method of characteristics. The equivalent circuits for such simulations are also analyzed by considering the system as having a linear time-varying source. It is found that the results from the load method are quite sensitive to the change of cylinder pressure or valve profile, in contrast to those from the direct method. In the load method, the source admittance turns out to be predominantly dependent on the valve admittance at the calculation frequency as well as the valve and load admittances at other frequencies. In the direct method, however, the source resistance is always positive and the source admittance depends mainly upon the zeroth order of valve admittance.

Journal Article↗
PubMed2005

Long range acoustic imaging of the continental shelf environment: the Acoustic Clutter Reconnaissance Experiment 2001.

An active sonar system is used to image wide areas of the continental shelf environment by long-range echo sounding at low frequency. The bistatic system, deployed in the STRATAFORM area south of Long Island in April-May of 2001, imaged a large number of prominent clutter events over ranges spanning tens of kilometers in near real time. Roughly 3000 waveforms were transmitted into the water column. Wide-area acoustic images of the ocean environment were generated in near real time for each transmission. Between roughly 10 to more than 100 discrete and localized scatterers were registered for each image. This amounts to a total of at least 30000 scattering events that could be confused with those from submerged vehicles over the period of the experiment. Bathymetric relief in the STRATAFORM area is extremely benign, with slopes typically less than 0.5 degrees according to high resolution (30 m sampled) bathymetric data. Most of the clutter occurs in regions where the bathymetry is locally level and does not coregister with seafloor features. No statistically significant difference is found in the frequency of occurrence per unit area of repeatable clutter inside versus outside of areas occupied by subsurface river channels.

Journal Article↗
PubMed1990

Potentiation of the acoustic startle response by a conditioned stimulus paired with acoustic startle stimulus in rats.

The hypothesis that the standard acoustic startle habituation paradigm contains the elements of Pavlovian fear conditioning was tested. In a potentiated startle response paradigm, a startle stimulus and a light conditioned stimulus (CS) were paired. A startle stimulus then was tested alone or following the CS. Freezing behavior was measured to index conditioned fear. The startle response was potentiated on CS trials, and rats froze more in CS than in non-CS periods. In Experiment 1, response to a previously habituated, weak startle stimulus was potentiated. In Experiment 2, response to the same stimulus used as the unconditioned stimulus (US) in training was potentiated. This CS-potentiated response retarded the course of response decrements over training sessions as compared with an explictly unpaired control group. Conditioned fear is a standard feature of this habituation paradigm, serves to potentiate the startle response, and provides an associative dimension lacking in the habituation process per se.

Animals↗
PubMed1987

[Complementary acoustic EEG control while recording early acoustically evoked potentials].

An easily performed method for the additional acoustical assessment of the EEG quality by the investigator during recording of human brainstem potentials is presented. By means of feedback of the audibly transposed "noiselike" EEG voltage to the opposite ear of the examined subject (instead of the usual masking noise) the subject can perceive self-produced disturbances (muscle activities) and minimize them for the period of examination. An example shows how this additional rejection of artifacts via "biofeedback" can effectively support methods that are already in use.

Audiometry, Evoked Response↗
PubMed1975

[Bilateral tumors of the acoustic nerve and Recklinghausen's disease observed in several generations. Considerations on heriditary acoustic nerve tumors].

Since 1933, four families have been found in Marseilles with bilateral tumours of the acoustic nerve spread over three generations in three families. The fourth only showing a cutaneous neuro-fibromatosis in the second generation. The authors recall briefly the clinical characteristics and compare their cases with similar ones found in the literature. Bilateral and familial neurinomas of the VIIIth cranial verbes were found in 21 families, making a total of 111 cases, unilateral neurinoma being used as a term of comparison. Among the groups of cases published, the family observed by Gardner and Frazier is the most remarkable (43 cases over 6 generations). From the hereditary point of view, the phenomenon of antiposition is not always constant. From the evolutionary point of view, bilateral neurinomas manifest themselves earlier clinically than unilateral ones. As far as associations are concerned, cutaneous manifestations of neuro-fibromatosis are the most frequent if the neurinomas are bilateral and non familia. Among tumors of the nervous system, meningiomas and gliomas have been found, other dysembryoplastic or degenerative tumoral associations being rare. The incidence of cutaneous symptoms is very low when the neurioma is unilateral. The association of cutaneous symptoms with bilateral and familial neurinomas does not worsen the prognosis, but the presence of such cutaneous signs is significantly more serious if the neurinoma is isolated. These considerations do no more than touch the fringes of the problems raised by these sporadic or hereditary tumours of the VIII the cranial nerves, developing within the framework of phacomatosis. Great caution is necessary in assessing the correlations observed in view of the narrow range of statistics available.

Deafness↗
PubMedDate not supplied

[Morphological and functional modifications of the acoustic system in golden hamsters with acoustic generalized epilepsy].

We studied the role of the neuronal circuit consisting of the superior olive-cochlear hair cells-auditory nerve complex in the pathophysiology of reflex audiogenic generalized epilepsy in the epileptic golden hamster. A direct role of the auditory function can be assumed from the genetic lesions found in these animals' acoustic system. These animals are a model of the anatomopathologic substrate of a type of hereditary neurosensorial hypoacusia.

Animals↗