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At least 667 records · Page 37Linked to original sources
PubMed2005

Effect of the temporal pattern of contralateral inhibition on sound localization cues.

We studied the temporal coding properties of identified interneurons in the auditory system of crickets, using information theory as an analytical tool. The ascending neuron 1 (AN1), which is tuned to the dominant carrier frequency (CF) of cricket songs, selectively codes the limited range of amplitude modulation (AM) frequencies that occur in these signals. AN2, which is most sensitive to the ultrasonic frequencies that occur in echolocation calls of insectivorous bats, codes a broader range of AM frequencies, as occur in bat calls. A third neuron, omega neuron 1 (ON1), which is dually tuned to both ranges of carrier frequency, was shown previously to have CF-specific coding properties, allowing it to represent accurately the differing temporal structures of both cricket songs and bat calls. ON1 is a source of contralateral inhibition to AN1 and AN2, enhancing binaural contrast and facilitating sound localization. We used dichotic stimulation to examine the importance of the temporal structure of contralateral inhibition for enhancing binaural contrast. Contralateral inhibition degrades the coding of temporal pattern by AN1 and AN2, but only if the temporal pattern of inhibitory input matches that of excitation. Firing rate is also decreased most strongly by temporally matched contralateral inhibition. This is apparent for AN1 in its mean firing rate; for AN2, high-frequency firing is selectively suppressed. Our results show that the CF-specific coding properties of ON1 allow this single neuron to enhance effectively localization cues for both cricket-like and bat-like acoustic signals.

Acoustic Stimulation↗
PubMed2001

Pineal organ-like organization of the retina in megachiroptean bats.

Phylogenetically originated from photoreceptive structures, the pineal organ adapts the organism to circadian and circannual light periodicity of the environment, while the retina develops to a light-based locator. Bats have a nocturnal life and an echolocator orientation presumably modifying the task of photoreception. Looking for morphological basis of the special functions, in the present work we compared the fine structure and immunocytochemistry of the retina and pineal organ in micro- and megacrochiroptean bats. We found that there is a high similarity between the retina and pineal organ in megachiropterans when compared to other species investigated so far. Besides of photoreceptor derived pinealocytes, the pineal organ of both micro- and megachiropterans contain intrapineal neurons and/or ganglionic cells as well as glial cells. Like spherules and pedicles of retinal photoreceptors, axon-type processes of pinealocytes form synaptic ribbon containig terminals. Similar to retinal photoreceptors and neurons, pinealocytes and pineal neurons contain immunoreactive glutamate and aspartate. In addition, excitatory amino acids accumulate in the pineal neurohormonal endings and might have a role in the hormonal (serotonin?) release of the organ. Concerning the structure of the retina the highest similarity to the organization of the pineal organ was found in the megachiroptean fruit eating bats Cynopterus sphinx and Rusettus niloticus. The retina of these species forms folds and crypts in its photoreceptor layer. This organization is similar to the folds of the pineal wall successively developed during evolution. Since a folded photoreceptor layer is not viable for a photolocator screen in decoding two-dimensional images, we suppose that this peculiar organization of the megachiropteran retina is connected to a "pineal-like" photometer task of the eye needed by these species active at night.

Animals↗
PubMed2004

Vocal mechanisms in birds and bats: a comparative view.

Vocal signals play a very important role in the life of both birds and echolocating bats, but these two unrelated groups of flying vertebrates have very different vocal systems. They nevertheless must solve many of the same problems in producing sound. This brief review examines avian and microchiropteran motor mechanisms for: 1) coordinating the timing of phonation with the vocal motor pattern that controls its acoustic properties, and 2) achieving respiratory strategies that provide adequate ventilation for pulmonary gas exchange, while also facilitating longer duration songs or trains of sonar pulses.

Animals↗
PubMed1976

[Early diagnosis of acute hematogenic osteomyelitis in children].

As evidenced by the author's findings, the use of the method of ultrasonic echolocation of long tubular bones facilitates the recognition of acute osteomyelitis in the stage of intramedullary abscess and also makes it possible to reduce the number of diagnostic errors and improve the results of treatment.

Acute Disease↗
PubMed1999

Auditory perception of walls via spectral variations in the ambient sound field.

Individuals with visual disabilities often use their hearing in order to maintain a line of travel parallel to walls, such as when walking down a hallway or along the side of a building. Previous studies established that this ability depends on the sense of hearing, but the specific acoustic information has not been investigated. The present paper describes a model of how sound pressure builds up within a meter or so in front of a wall, particularly in the low frequency end of the sound spectrum. This buildup of sound pressure is based on ambient or "background" sound, not self-produced sound such as footsteps. The model leads to a prediction that walls are detected by means of a spectral shift toward low frequencies. This prediction was tested in three experiments, in which sighted adults listened for such spectral shifts. In each experiment, a threshold value was obtained corresponding to the farthest simulated distance from a wall that could be detected. Threshold values were in good agreement with previous observations of the distance at which pedestrians can utilize acoustic information from walls. There was no evidence that simulated listener motion enhanced perception of walls. The model underlying these experiments implies that the term echolocation carries inappropriate connotations about the auditory processes that are involved in walking along walls. It is suggested that a more apt description is that pedestrians listen for spatial variations in the structure of the ambient sound field.

Adult↗
PubMedDate not supplied

[The diagnostic and surgical characteristics of gunshot nonmagnetic intraocular fragments].

Results of treatment of 42 patients with a magnetic intraocular fragments (balls, pistons, capsules) are analyzed and indications for various surgical interventions for removal of fragments with the minimal injury for the eye are defined. The role of echo diagnosis (together with x-ray diagnosis and computer-aided tomography) in the selection of operative access to a foreign body and, specifically, echolocation on the operative table during surgery is shown. Combination of informative diagnostic methods with advanced surgical technologies helps save the organ and attain functional results in this extremely grave posttraumatic pathology.

Adolescent↗
PubMedDate not supplied

[Noise resistance of the dolphin auditory analyzer as a function of the directional angle of the noise].

Masked tonal thresholds by noise in the bottlenose dolphin have been measured as a function of angle of noise direction. Sharp directional selectivity of hearing has been discovered resulting in an abrupt decrease of noise masking with the increase of the angle of noise coming. It has been shown that narrow directional characteristics of hearing is an angle 8 degrees plus or minus 2 degrees for the level of minus 3db. It is one of the main mechanisms supplying the echolocation system of the dolphin with the high level of resistance to noise.

Animals↗
PubMed1976

[Characteristics of the reactions of bat superior olivary neurons to single and paired ultrasonic stimuli].

Characteristics of single-unit activity in the superior olivary complex of Rhinolophus ferrum-equinum in response to ultrasonic stimuli with a pulse frequency within the echolocation range were studied. Some neurons were found to have three separate response areas with characteristic frequencies corresponding to one half and one third of the basic frequency ranging from 80 to 86 kHz. When the intensity of stimulus with a pulse frequency equal to the characteristic neuron frequency increased, the tonic response changed into phasic activity. With the use of two overlapping stimuli a change from phasic to tonic response occurred. The frequency of tonic discharge corresponded precisely to that of beats up to 2000 Hz (synchronism of neuronal discharges with each beat cycle). Synchtonized tonic activity persisted under specific pulse frequencies and stimulus intensities.

Animals↗
PubMed1992

[Ultrasonography of the gallbladder in patients with hemoblastoses].

A total of 402 patients with acute or chronic leukemia and chronic cholecystitis and 100 healthy controls were exposed to ultrasonic biliography. It was revealed that leukemic infiltration of the bladder wall, increased pressure in the portal system, hypoalbuminemia and the concurrent diseases of the bladder could be the main causes of the alterations in the size and form of the bladder and the width of its walls in hemoblastosis patients. It was stated as well that the thickening of the bladder wall was an obligatory diagnostic criterion for not only chronic cholecystitis but various patterns of hemoblastoses as well. The authors suggested that echolocation of the gall bladder should be done in combination with clinical and morphological verification of the tumor process and its stages that undoubtedly would be of significant value in the choice of therapeutic policy.

Adolescent↗
PubMed1992

[Diagnosis and treatment of postoperative bile peritonitis].

Over 7 years the authors had 37 cases of biliary peritonitis, in 19 of which the complication occurred after operation on the liver and biliary tract. The clinical picture was determined by the amount and rate of escape of bile into the abdominal cavity. The course of biliary peritonitis is often masked because the disease has no specific signs. Ultrasonic echolocation is used in making its diagnosis, it shows accumulation of fluid in the projection of the cystic seat and in the subhepatic space. Among 19 patients who underwent a repeated operation 6 died. Death was caused by progressive peritonitis, hepatorenal failure, thromboembolism of the pulmonary artery.

Bile↗
PubMed2005

Spontaneous, generalized lipidosis in captive greater horseshoe bats (Rhinolophus ferrumequinum).

During a routine 6-month quarantine period, 3 of 34 greater horseshoe bats (Rhinolophus ferrumequinum) captured in mainland China and transported to the United States for use in echolocation studies were found dead with no prior history of illness. All animals were in good body condition at the time of death. At necropsy, a large amount of white fat was found within the subcutis, especially in the sacrolumbar region. The liver, kidneys, and heart were diffusely tan in color. Microscopic examination revealed that hepatocytes throughout the liver were filled with lipid, and in some areas, lipid granulomas were present. renal lesions included moderate amounts of lipid in the cortical tubular epithelium and large amounts of protein and lipid within Bowman's capsules in the glomeruli. In addition, one bat had large lipid vacuoles diffusely distributed throughout the myocardium. The exact pathologic mechanism inducing the hepatic, renal, and cardiac lipidosis is unknown. The horseshoe bats were captured during hibernation and immediately transported to the United States. It is possible that the large amount of fat stored coupled with changes in photoperiod, lack of exercise, and/or the stress of captivity might have contributed to altering the normal metabolic processes, leading to anorexia and consequently lipidosis in these animals.

Animals↗
PubMed1990

[Use of the CO2 laser in the surgical treatment of complicated echinococcosis of the liver].

The article discusses experience in the use of high-energy CO2 laser in the treatment of 108 patients with complicated forms of echinococcosis of the liver. The diagnostic efficacy of instrumental methods of examination is determined. The most informative are ultrasonic echolocation (96.8%) and computered tomography (100%). They allow exact localization of the cyst, which is important in the choice of the operative approach. The use of the laser for excising the fibrous capsule and treating the residual cavity makes is possible to: abandon the traditional methods for completing echinococcectomy (drainage of the residual cavity, marsupialization, capitonnage), exclude suppuration of the residual cavity, reduce markedly the period of the patient's hospitalization.

Adolescent↗
PubMed1990

[Histologic studies of cartilaginous structures in the anterior region of the head of the sperm whale Physeter macrocephalus].

Recently discovered cartilaginous structures in the forehead of the sperm whale (Behrmann and Klima 1985) were investigated histologically. The largest and most important of these structures is the nasal roof cartilage which can be derived from the tectum nasi, a part of the embryonic nasal capsule (Klima et al. 1986). In the investigated sperm whale fetuses, this structure consists of embryonic hyaline cartilage which is well suited for morphogenetic processes and fast growth. In the investigated adult sperm whale, the originally hyaline cartilage has been transformed into a special kind of elastic cartilage. The arrangement of cells, territories, and extracellular substance resembles hyaline cartilage. This component represents an adaptation to pressure load. The appearance and arrangement of elastic fibres resembles elastic cartilage. This component is an adaptation to distortion forces. Obviously, pressure and distortion are the strongest mechanical strains that the nasal roof cartilage is exposed. We see the function of this cartilage structure therein that, being a pressure-elastic skeletal support and following the left nasal meatus along its whole extension through the massive and soft forehead, it secures the only direct respiratory passage. Additionally, fibre bundles of transversely striated muscles are anchored in the perichondrium of the nasal roof cartilage. The function of this delicately interwoven muscle system is seen by us in the fine tuning of contraction and dilatation of the respiratory passage. Moreover, a possible function as a sound conducting cartilaginous structure serving the echolocation system is considered (c.f. Pilleri et al. 1983).

Animals↗
PubMed1989

Noradrenaline enhances temporal auditory contrast and neuronal timing precision in the cochlear nucleus of the mustached bat.

In the mustached bat, Pteronotus parnellii, noradrenaline (NA) was applied iontophoretically to single units in the anteroventral cochlear nucleus. NA suppressed tonic components of auditory responses and enhanced phasic onset responses to pure tone stimuli. The enhancement of onset activity was most pronounced in awake bats and was due to a decrease in the latency jitter of the first tone-evoked spikes from 0.55 msec in controls to 0.28 msec during NA application. In addition, NA reduced spontaneous neuronal activity. Noradrenergic antagonists suppressed phasic onset activity and increased the latency jitter of onset spikes. Opposite to the effect of NA, the tonic response component increased during application of the beta-antagonist propranolol but decreased during injection of the alpha 1-antagonist corynanthine. Other putative transmitter substances tested, nonselectively depressed both phasic and tonic response components (GABA, glycine) or increased both components either similarly or had more pronounced effects on the tonic response components (ACh, glutamate). Thus, NA specifically enhances auditory temporal contrast in favor of transients and improves neuronal timing precision, which may be of relevance for auditory tasks like passive sound localization, echolocation, and recognition of temporal patterns.

Acetylcholine↗
PubMed1989

[The potentials of one-dimensional ultrasonic diagnosis in severe injuries to the chest cavity].

The author demonstrates the diagnostic possibilities of an ultrasonic examination of severe injuries of the chest by a one-dimension echolocation method on the basis of experimental and clinical tests of a modernized ECHO-P apparatus and a sensor. Synonymous and repeated acoustic characteristics of lung contusions, hemo- and pneumothorax have been revealed and described. The obtained data are of practical interest with regard to express diagnosis of the complicated chest injuries at the preclinical and early clinical stages of the treatment of the patients.

Cadaver↗
PubMed1986

[Non-invasive methods of examination in the diagnosis of aneurysms].

Radionuclide angiography and ultrasonic echolocation were used for the examination of 38 patients with aneurysms. Isotope angiography was fulfilled in all the 38 patients, ultrasonography was used in 20 patients. Radionuclide angiography and ultrasonography are thought to be sufficiently effective methods of diagnosis of vessel aneurysms.

Adult↗
PubMedDate not supplied

[Features of volume and pressure pulsations during changes in "reserve space" within the cranial cavity].

Changes in the amplitude and phase characteristics of pulse variations of volumes and pressures in response to an increase in the intracranial pressure are discussed. The study of 60 neurosurgical patients has shown that as the intracranial (subdural) pressure grows the amplitude of pulse variations of subdural pressure increase to 30 mm Hg and then decreases, the phase characteristics of the pulse waves changing accordingly. The changes in the amplitudes of pulse variations produced by mechanical displacement of the walls of cerebral lateral ventricles measured with the aid of the noninvasive ultrasonic method suggest that an increase in the CSF pressure above 200 mm H2O makes the intracranial cavity too "tight", which depletes the reserve spaces of the cerebrospinal system. If the above changes develop consistently, then it can be assumed that each of the pressure ranges isolated can be characterized by amplitude-phase parameters of pulse waves that form a specific pattern. Taking into consideration the potentials of noninvasive measurements of amplitude-phase characteristics of the intracranial pulse wave by means of ultrasonic echolocation, it deems possible to develop noninvasive techniques for measuring compensatory abilities of the cerebrospinal system.

Biomechanical Phenomena↗