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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
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↗
PubMedDate not supplied

[Frequency following response to cochlear nuclei in cats to polycomponent sonic signals].

Under chloralose-urethane anaesthesia, by means of spectrograms and dynamic spectrograms studies have been made on frequency following response (FFR) in the cochlear nuclei of cats evoked by sonic stimulation. It was shown that FFR readily reproduces frequencies of the acoustic spectrum of separate tones and two-tonal harmonic complexes (the upper reproduced frequency in FFR - 6.0-6.5 kc/sec). The main deteils of the acoustic spectrum of the sounds of speech are also easily reproduced in FFR. Combination tones were observed in FFR during application of two-tonal harmonic complexes. The first harmonic is inhibited in FFR when combined with higher ones (the fifth or the sixth) or at certain phase angle between the first and the second harmonics ("doubling" phenomenon).

Acoustic Stimulation↗
PubMedDate not supplied

[The combined activities of the temporal cortical area and hippocampus in man during the localization of a moving sound image].

In patients with epileptic lesions in the cortex and mediobasal structures of the brain, studies have been made on the perception of spatial position of sound images during dichotic stimulation. It was established that the extreme interval which is necessary for formation of sensation of the moving sound image increases during right-side lesions of the temporal cortex. During left-side lesion of the temporal lobe, more diffuse disturbances in the trajectory of image movement (from the right and left) are observed, whereas right-side lesions result in disturbances of movement only at the opposite side of the latter. Cortical lesions and those in the mediobasal parts of the temporal lobe are accompanied by identical gradient of disturbances in the trajectory of sound image movement and short-term imprinting of succession of signals which differ with respect to their spatial position. Maximum disturbances are observed during lesions in the cortical and mediobasal parts of the temporal lobe, whereas only cortical lesions or only hippocampal lesions result in less significant disturbances. It is suggested that combined activity of the auditory cortex and hippocamp is necessary for localization of a sound source.

Acoustic Stimulation↗