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Biomedical subjects

S F Vaĭtulevich

Publications and source records attributed to S F Vaĭtulevich.

At least 19 recordsLinked to original sources
PubMed2004

[A mismatch negativity elicited with stationary and moving auditory images of different azimuth positions].

Characteristics of mismatch negativity elicited by dichotic stimulation were examined using deviant stimuli simulating movement of fused auditory images towards the standard stimuli or in the reverse direction. The effect of stationary deviants localized at 90 degrees in respect to standards was also measured. The standard stimuli were localized near either of ears or along the head midline. The spatial locations were produced by introducing interaural time differences into the click trains. All deviant stimuli evoked the mismatch negativity. The deviants moving from standards seem to evoke the lowest mismatch negativity with the longest latency at all azimuthal locations of standard stimuli. Besides, the deviant shift from standards proved to be the only direction at which the characteristics of mismatch negativity depended upon the standard's azimuth. It is seems that the discrimination of interaural time delay is essentially dependent on the pattern of interaural delay changes at the moment when the deviant occurs.

Acoustic Stimulation↗
PubMed2003

[Role of phasic changes in sound signal in localization of auditory image].

The work presents experimental data on certain changes in electrical responses of the auditory system's midbrain centre in a contraphasic binaural presentation of sound impulse series. Neuronal cortical activity is selective in respect to dynamic interaural changes of signals' phasic spectre which may serve as a basis for the mechanisms of localising a moving source of sound. Human auditory evoked potentials reveal a manifestation of memorizing the auditory image movement direction as shown by appearance of stimuli deviant from standard mismatch negativity.

Acoustic Stimulation↗
PubMed2002

[Changes of evoked potentials caused by sound signals with different localization characteristics].

Characteristics of the mismatch negativity (MMN) were studied by presenting the subjects with four blocks of stimuli containing standard series of clicks (90%) simulating a stationery sound image located in the head midline, and one of three different deviant series of clicks (10%) simulating either a stationary sound image located near the left ear or a moving sound image which shifted from the head midline to the left ear or in the opposite direction. All the deviant stimuli elicited the MMN with the minimal peak amplitude and the greatest latency evoked by the deviant series of clicks simulating the sound image moving from the head midline to the left ear. These findings suggest that the MMN may be considered as a pre-perceptual physiological measure of the discrimination accuracy for the sound signals with various spatial locations.

Acoustic Stimulation↗
PubMed2000

[Comparison of binaural release from forward masking in animals and humans. Electrophysiologic study].

The EPs of the inferior colliculus and auditory cortex in anaesthetized guinea pigs and the long latency auditory EPs in alert humans were studied. The stimuli consisted of binaurally presented pairs of clicks used as a masker, and the probe, with a variable time delay between them. The greatest relative differences between out-of-phase and in-phase probe responses were observed at the beginning of the recovery course. They averaged as 1.6, 1.5 and 1.4 for the responses of the inferior colliculus, auditory cortex and long latency potentials, resp., at the stimuli intensities of 50-65 dB SPL, and then decreased to zero during the time course of the probe response recovery. Correlation of this parameter with the stimulus intensity was positive.

Acoustic Stimulation↗
PubMed1987

[Long-latency human auditory evoked potentials and localization of an acoustic pattern].

Data are presented on: reflection of bordering conditions for formation of movement of the sound image in long-latency auditory EPs, and reflection of the important feature of human localizing function, i.e. resistance against interference in localizing both the immobile and the moving sound image, in long-latency auditory EPs. Alteration of the signal parameters inducing the sensation of the sound image movement, was found to lead to exaltation of amplitudes of the N1 and P2 components. Effect of binaural freeing from masking is reflected in these same components of long-latency auditory EPs in perception of spatially translocating signals.

Adult↗
PubMedDate not supplied

[Tendencies in auditory physiology].

Main tendencies in studying of human and animals auditory system with psychoacoustical and electrophysiologycal methods are considered. Concerning psychoacoustical studies some basic data are presented as well as contemporary tendencies in hearing physiology in analysis of the intensity, frequency, temporal characteristics of the sound signals and data related to such phenomena as masking and adaptation. Data concerning directional hearing are presented in detail as a basis of auditory virtual reality. In electrophysiological studies of the auditory system detailed analysis of mapping in auditory centers and mechanisms concerning localization of unmoved and moving auditory stimuli was performed. Special attempt was paid to consider the reflection of different types of auditory signals in human evoked potentials.

Animals↗
PubMedDate not supplied

[The effect of the rate of movement of a sound image on human long-latency auditory evoked potentials].

In 10 healthy subjects, studies have been made on changes in amplitude-temporal characteristics of N1-P2 components at different rates of movement of a sound image (3.14, 1.57 and 0.78 rad/s). It was shown that only movement of the sound image from the right ear to the median line of the head with sufficiently high rate (3.14 rad/s) results in the increase in total peak amplitude of N1-P2 components relatively similar parameters obtained during the effect of a resting sound image lateralized at the same ear. Latent periods of N1 component in both hemispheres are longer during the effect of the moving sound image than during the effect of the resting lateralized one, although with the decrease in the rate the difference becomes less significant. It is suggested that the right hemisphere is more sensitive to changes in the rate of movement of the sound image.

Acoustic Stimulation↗
PubMedDate not supplied

[Long-latency auditory evoked potentials in humans exposed to sonic image movement].

Slow cortical auditory potentials have been studied in man during dichotic click train stimulation perceived as a moving sonic image. Higher values of the amplitude of N1 and P2 components were observed as compared to the response to unmoving image. The amplitude of these components gradually increases with changes in the click frequency within a train (from 15 to 60 Hz), the lower border of this band approximately corresponding to the time interval which is necessary for formation of the sonic image.

Acoustic Stimulation↗