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Ia A Al'tman

Publications and source records attributed to Ia A Al'tman.

At least 19 recordsLinked to original sources
PubMed2005

[The effect of auditory image moving in vertical plane upon posture responses of humans].

The influence of sound image motion on postural reactions was studied. The movement of sound source was created by successive switching of the loudspeakers situated over the arc in sagittal plane. Movement duration of sound stimulus was 1.6 s, 3.2 s and 4.8 s. The mean sway magnitudes decreased when the stimuli duration was 1.6 s and 3.2 s. Averaging of the wave-forms of center-of-pressure sway for signal with 4.8 s duration revealed that the sound image presentation induces body displacement in the direction opposite to that of sound image.

Adult↗
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↗
PubMed1999

[Properties of the derived cochlear action potential during tonal forward masking in guinea pigs].

In awake preimplanted guinea pigs, characteristics of auditory nerve and derived action potentials were investigated using a pure-tone forward masking paradigm. Auditory nerve action potentials are recorded from round window. The derived potential was obtained by subtracting the masked action potential from unmasked response. The results show that the derived potential is more sensitive to changes in auditory nerve action potential during masking than widely used indicator of masking--the decrement in auditory nerve action potential. Derived response reflects the response changes both in amplitude and waveform induced by masker. The differences between the auditory nerve and derived action potentials suggest that the amplitude and time changes in the derived potential give a more detailed information on the characteristics of the auditory nerve fibers responses.

Action Potentials↗
PubMed1999

[Characteristics of sound source movement perception as a basis for acoustic vertical construction].

The subject of inquiry was perception of moving sound along the vertical at various angular velocities. The sound was switched around by 13 sequential dynamics installed on a 180 degrees arc. Threshold values for discriminating angular velocities at 150, 167, 188, 214, 250, 300, 375, and 500 degrees/s were measured with the minimal borderlines method. Six test-subjects with normal hearing participated in the experiment. Acceleration of sound movement in the range from 167 up to 500 degrees/s leads to essentially linear increases in absolute threshold values and monotonous increases in relative threshold values.

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↗
PubMed1984

[Spatial characteristics of the reaction of the inferior colliculi in the cat to movement of the sound source].

The EP-series response of the inferior colliculus to clicks simulating sound source motion, reflects characteristics of this "motion" ("the motion effect", ME). ME distribution over the inferior colliculus practically coincided with the spatial distribution in cases when contralateral stimulation was more effective than the ipsilateral one. The spatial distribution in cases with no ME was identical with the distribution of cases of equal effectiveness of the contra and ipsilateral stimulations. The ME was shown to be connected with the binaural inhibitory effects and might probably be related to the activity of two main neuronal groups (the principal and multipolar ones).

Acoustic Stimulation↗
PubMed1983

[Patterns of the reaction of the inferior colliculus to the movement of a sound source in the cat].

Series of slicks simulating source sound movement caused 82% of the posterior colliculus' EPs to alter gradually their amplitude and/or shape ("the movement effect"). The markedness of ipsilateral effect was about 1.5 times higher than that of the contralateral one. The effect occurred within large range of velocities: no lower than 3.4 rad/sec in 65% of observations. The most effective were the velocities over 6.8 rad/sec in 78%. Difference in responses to opposite directions of the sound source movement occurred in 26%. The movement effect obviously depended on the site of EP recording.

Acoustic Stimulation↗
PubMed1981

[Selectivity of trace reactions of medial geniculate neurons to the rate of simulated movement of a sound source in the cat].

33 out of 90 neurons of the cat medial geniculate body revealed the selectivity of their afterdischarges to movement of sound when velocity of the movement changed from 30 to 180 deg/s. There was a specific velocity of the movement for each neuron. 76% of the neurons preferred the movement of 45--90 deg/s. 9 neurons had a periodic character of responses. The selective afterdischarges occurred in 39% of dorsal neurons and in 39% of ventral ones. The afterdischarges can be dependent on the direction of sound source movement, too.

Animals↗
PubMed1981

[Response of medial geniculate body responses to the velocity of simulated sound source movement in the cat].

36 neurons (39%) of the anaesthetized cat medical geniculate body responded to simulated motion of the sound source (with angular velocity of 30 to 180 degrees/sec) selectivity with a certain speed of firing rate changing specific for each neuron during action of the signal. Selective response to a certain velocity of the sound motion occurred in 55% of neurons of the dorsal portion and in 27% of the ventral portion of the medial geniculate body. Response of these neurons reflected the whole range of experimental velocities. 75% of neurons revealed most obvious responses to the sound motion velocity of 30--90%/sec. The selective response to a certain velocity of the sound motion seems to depend on the direction of motion.

Animals↗
PubMed1980

[Effect of interaural phase differences on inferior colliculus activity during binaural stimulation with tonal signals].

The frequency-following response (FFR) of the inferior colliculus depends greatly of the interaural phase differences (delta phi). The function of the FFR amplitude of delta phi shows periodicity, with different phase shifts (in relation to delta phi = 0) at different electrode location and with different sound frequencies or intensities. The maximal FFR sensitivity (in microV) to delta phi (in degrees) may be as high as 60 microV/10 degr. or for interaural time differences--15 microV/10 microsec. Such a sensitivity might provide for binaural phase sensitivity near to the sensitivity of the human auditory system.

Animals↗
PubMed1980

[Electrophysiologic manifestations of the functional organization of the inferior colliculi of cats during binaural stimulation with different tonal signals with interaural phase differences].

The maximal activity of the inferior colliculus studied with frequency following responses was mainly observed at interaural phase differences delta phi of 180 degrees, the minimal activity at delta phi = 135-180 degrees (with contralateral delay), and the maximal asymmetry of the activity occurred mainly at delta gamma of 90-135 degrees. These values are statistically independent of both the stimulus frequency and electrode location within the inferior colliculus. These findings support observations on single unit activity and are considered as possible basis for relative estimation by the auditory system of the degree of the sound source shift from the head midline, in addition to the absolute estimation on the basis of the characteristic delay mechanism. The data obtained allow to suggest possible neurophysiological mechanisms underlying some psychophysiological phenomena concerning the shift of the fused auditory image.

Animals↗