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Biomedical subjects

S F Vaitulevich

Publications and source records attributed to S F Vaitulevich.

8 recordsLinked to original sources
PubMed2005

Effects of the azimuthal position of stationary and moving sound images on the mismatch negativity phenomenon.

This report presents results obtained from studies of the phenomenon of mismatch negativity in conditions of dichotic stimulation with presentation of deviant stimuli modeling movement of a sound image towards or away from a standard stimulus and on presentation of stationary deviants located at an angle of 90 degrees to the standard. Standard stimuli were located close to the left or right ear or in the midline of the head. All deviant stimuli induced mismatch negativity. Movement of the deviant stimulus from the standard was found to induce mismatch negativity with the longest latency and smallest amplitude for all azimuthal positions of the standard stimulus. In addition, it was only in this direction of movement that there was a relationship between measures of mismatch negativity and the azimuth of the standard. It was suggested that the process of the recognition of differences between interaural delay times is significantly dependent on the nature of changes in this parameter at the moment at which the deviant stimulus is presented.

Acoustic Stimulation↗
PubMed2004

Changes in evoked potentials during the action of sound signals with different localizing characteristics.

This report presents results of studies of the phenomenon of mismatch negativity (MMN) during exposure to four blocks of sound stimuli each containing identical standards creating an immobile sound image located along the midline of the head and one of a set of deviants, creating a sound image located either by the left ear or moving from the midline of the head towards the left ear or in the opposite direction. All deviants induced mismatch negativity; the minimal amplitude and longest latent period were seen in the mismatch negativity produced by the deviant modeling movement of the sound image from the midline of the head to the left ear. The question of the appearance of mismatch negativity as a criterion for the accurate discrimination of signals with different localizing characteristics is discussed.

Acoustic Stimulation↗
PubMed2004

The role of phase changes in sound signals in localization of sound sources.

The auditory system in humans and animals makes virtually no discrimination of phase changes in the structure of monaurally presented sound signals. However, electrophysiological studies have demonstrated marked changes in the responses of the central parts of the auditory system when the phase structure of the signal changes during presentation of the same type of stimulation. We have suggested that this inconsistency is due to the preparative role of phase effects during monaural stimulation for subsequent operations in the auditory system involved in determining the location of a sound source in space. This report presents experimental data on defined changes (increases in amplitude) in the electrical responses of the midbrain center of the auditory system (inferior colliculus) in antiphase binaural presentation of series of sound impulses (comparison with synphase presentation). These changes may be part of the mechanism underlying the interference resistance of the auditory system during determination of the location of a sound source (binaural release from masking). Neuronal cortical activity is sensitive and selective to dynamic interaural changes in the phase spectrum of the signal, which may provide the basis of the mechanism for locating a moving sound source. Auditory evoked potentials in humans demonstrate memorizing of the direction of movement of a sound image, as shown by the changes in parameters on presentation of stimuli of different locations (deviant stimuli) differing from the standard parameters of mismatch negativity.

Acoustic Stimulation↗
PubMed1990

Auditory image movement in evoked potentials.

Long-latency auditory evoked potentials (AEPs) were tested in subjects following binaural stimulation with click trains with gradually changing interaural time delays (delta Ts). With appropriate change of the delta Ts this sound signal could produce the sensation of a moving fused auditory image (FI). It was found that the N1-P2 complex of the AEPs rose in amplitude with the increase of the click rate above 15 Hz, and to a greater extent for the moving than for the unmoved FIs. Binaural release from masking (as measured by the binaural masking level difference (BMLD) for the AEPs) amounted to 6 dB for the unmoved FI. For the moving FI the BMLD for the AEPs amounted to 2.8 and 3.5 dB in men and 13.4 and 11.3 dB in women, for the left and right hemispheres respectively. The amplitude of the N1-P2 complex following stimulation with the 'moving' and 'unmoved' sounds was larger in women than in men.

Adult↗
PubMed1984

Responses of the swimbladder of the carp to sound stimulation.

The oscillations of the swimbladder anterior chamber of the carp (Cyprinus carpio) following stimulation with tones of 300-1500 Hz were studied by the method of holographic interferometry. The oscillation amplitude appeared to be maximal at frequencies close to the resonance frequency of an air bladder of equivalent volume as well as at frequencies corresponding approximately to the second and third harmonics of the resonance frequency. A change in the frequency of the sound signal or in the instantaneous pressure amplitude could result in spatial displacement of the oscillation centers on the swimbladder wall. The interference picture which resulted from recording the swimbladder oscillations over the tested frequency range was not observed on the holograms recorded within 20-24 h after the fish had been killed.

Acoustic Stimulation↗
PubMedDate not supplied

Long-latency auditory evoked potentials in humans and the localization of a sound image.

In the article, we discuss data from an investigation concerning how boundary conditions for the creation of sound-image movement are reflected long-latency auditory evoked potentials and discuss how and important associated with the human localizing function (resistance to interference during the local localization of both a stationary and a moving sound image) appears in long-latency auditory evoked potentials. We establish that a change in the parameters of a signal creating a sensation of sound-image movement results in an exhaltation of t he amplitudes of the N1 and P2 components. The effect of binaural freedom from masking is reflected in these same components of long-latency auditory evoked potentials during movement of spatially shifting signals.

Acoustic Stimulation↗
PubMedDate not supplied

Comparison of binaural release from forward masking in animals and humans. Electrophysiological studies.

Evoked potentials in the inferior colliculus and auditory areas of the cortex were studied in anesthetized guinea pigs and long-latency auditory evoked potentials (LAEP) were studied in waking humans using sequential binaural presentation of pairs of clicks--the masker and the masked signal--with a variable interval between them, to provide the conditions needed for the psychophysical phenomenon of direct forward masking. Introduction of phase differences between the masker and the masked signal led to decreases in suppression of responses to the masked signal and to faster recovery of the reaction types recorded. The greatest relative differences between response magnitudes to antiphase and synphase masked signals were seen at the beginning of the recovery process, and were 1.6, 1.5, and 1.4 respectively for responses from the inferior colliculus, auditory area of the cortex, and LAEP at stimulus intensities of 50-65 dB sound pressure level, differences subsequently decreasing to zero. There was a positive correlation between this measure and the stimulus intensity. The greatest differences between the time at which the recovery process ended for responses to antiphase and synphase masked signals were 4, 250, and about 2000 msec respectively for the inferior colliculus, auditory area of the cortex, and LAEP.

Acoustic Stimulation↗