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I A Vartanian

Publications and source records attributed to I A Vartanian.

At least 19 recordsLinked to original sources
PubMed2003

[Dependence of the mouse inferior colliculus neurons activity on position and direction of movement of the spectral contrast].

Response variability of the single neurons of the inferior colliculus of mouse (Mus musculus) to series of noise bands and of notch noises with regular 1/12 octave steps of the band/notch center frequency and width of noise band/notch 1/3 octave, was studied. Neurons with strong inhibitory influence in excitatory response area (inhibitory-dominated) show low impulse activity when noise band exceeded excitatory response area. Spectral contrasts crossing the center of excitatory response area (at CF or nearly CF) were found to be the most efficient stimuli for such neurons. Neuron responses to spectral contrasts derived both from noise band and noise notch were identical. Approaching of inhibitory and excitatory inputs is expected to sharpen the auditory neurons frequency tuning to position of spectral contrasts, similar to neuronal processing in visual system. Neuron selectivity to the direction of spectral contrasts movement was determined in neuron response differences when the noise band or notch shifted from excitatory area to inhibitory areas as compared with shift in the opposite direction. Functional role of contrast mechanism for sound localization on the base spectral cues related to external ear transfer characteristics is discussed.

Acoustic Stimulation↗
PubMed2002

[Sensitivity of the neurons in the auditory inferior colliculus of mice to the direction of the shift of broadband spectral notch noise].

Series of a notch noise with regular shifts of the notch center frequency: one--from low frequencies to high frequencies and the other--from high frequencies to the low, were synthesized. The notch noise series imitated sound source vertical moving. Single neuron's responses of inferior colliculus of the house mouse (Mus musculus) to the notch-noises altered with notch central frequency varying through excitatory and inhibitory frequency response areas in neurones' receptive fields. The neural responses alteration to the notch noise varying depended on the bandwidth of notch. Disinhibition in inhibitory side band could be higher if the notch overlying the inhibitory areas followed the notch overlying the excitatory areas. The data obtained make it possible to consider the excitatory and inhibitory interaction as a mechanism of neural sensitivity to the notch moving direction. Neurones' response set could provide information about sound source moving over auditory space.

Acoustic Stimulation↗
PubMed2000

[Auditory analysis of the sound source approaching and withdrawing: psychoacoustic and neurophysiological correlates].

The findings seemed to be based on direction and velocity of modelling the radial sound source shifting in free acoustic field. The threshold and the optimal parameters of the acoustic model imitating the approaching and withdrawing of the sound source shifting in silence and under conditions of noise, were established. A correlation between peak-to-peak amplitudes of the N1-P2 components of auditory EPs and the imitated direction of the sound shifting, was shown. The role of different left and right hemispheres' areas in perception of the radial sound source was analysed. The detector features of the central auditory neurones were shown as a possible mechanism of estimating the sound source approaching and withdrawal.

Acoustic Stimulation↗
PubMed1999

[Modeling the frontal closing and departure of sound source].

Software modeling frontal back and forth movements of a sound allowed determination of the best combinations in which changes in amplitude and frequency of sound pulses sequence invoke distinct sensations of approaching or departing sound factually generated at one and the same spot no matter the distance from the listener.

Acoustic Stimulation↗
PubMed1998

[Characteristics of the response area of mouse inferior colliculus neurons within the critical band].

The inferior colliculus neurons which characteristic frequencies are in the range of 17-25 kHz, corresponding in mice to the width of psychophysical critical band with central frequency of 20 kHz, revealed all types of rate/level functions traditional to the auditory system neurons: monotonic, plateau and non-monotonic. Simultaneous presentation of two tones provide the following effects in the neuron response area: threshold sensitivity shift to high intensities; the reduction of intensity range within the neuron frequency response area; the increase of neurons selectivity to the stimulus frequency parameters, cause not only restriction of response exhibitory area, but threshold decrease on the CF stimulus. The finding suggest a coexistence of two inhibitory systems, one of which provides the stability of auditory system's frequency selectivity in the wide intensity range and the other regulating perception of signal intensity within neuron frequency area.

Acoustic Stimulation↗
PubMed1980

[Effect of acoustic stimulation parameters on human appreciation of changes in distance from a sound source].

Minimal time necessary for appearance of sensation of approaching or withdrawing of the amplitude-impulse-modulated sound was 0.3--0.4 sec at changing the intensity from minimal to maximal within the range of 30--60 dB over the threshold of rhythmic series determination (10--50 Hz). The number of short lengths of tones or noises in the series within this time epoch should be not less than three. The effect of the value of carrying frequency of the series lengths upon the sensation of approaching or withdrawing is only evident within the range of those temporal parameters of the signal which accompanied change of criterion of estimation of the sound quality. Further shortening of the signal leads to substitution of the criterion for estimation of stimulus position for the criterion of sound accentuation at a tonal carrier and for the criterion of consonant-likeness at a noise carrier. The downward frequency modulation from the initial frequency at a growing amplitude enhances the sensation of "approaching", the upward modulation enhances the sensation of source "withdrawing", as compared with the constant frequency or the frequency modulation of opposite sign.

Adult↗
PubMed1976

[Characteristics of the reactions of neurons of successive links in the auditory pathway to changes in the timing of acoustic signals].

Afferent impulsation was compared for different levels of the auditory system: the cochlear nuclei, posterior colliculi, and the auditory cortex. While moving from the cochlear nuclei over to the posterior colliculi and the auditory cortex, the number of neurons describing the temporal structure of the amplitude-modulated signal's envelope in the impulse activity pattern, becomes sharply reduced; the number of neurons selectively responding to certain phases of the envelope increases; the firing rate of neurons of the auditory pathway's higher levels decreases; the repetition rates becomes narrow due to limitation from both the high- and the low-frequency sides. Selectivity of responses to combination of such signal parameters as the frequency of the carrier and the rhythm of the amplitude modulation, increases. Specificity of the neuronal responses increases on certain combinations of such parameters of the frequency-modulated sounds as the frequency range in the signal, the direction and speed of the frequency modulation. The data obtained revealed some general tendencies of the impulsation transformation in successive levels of the auditory pathway.

Animals↗
PubMed1975

[Responses of inferior colliculus neurons to frequency modulated signals and the temporal characteristics of inhibitory interaction].

Comparison of neuronal responses (118 units) in the inferior colliculus of anesthetized rats to frequency-modulated (FM) sounds and time characteristics of two-tone inhibition were carried out. High sensitivity to certain direction of FM in 2/3 of neurons coincide with spatial characteristics of excitatory and nihibitory areas: their shape, width and arrangement. In 1/3 of neurons directional response specificity is shown to be determined by different time course of inhibitory process evoked by high-frequency and low-frequency tones.

Acoustic Stimulation↗
PubMed1975

[Frequency characteristics of central auditory neurons following a decrease in the number of periods of excitatory pure tones].

In anesthetized rats, frequency-threshold curves of the inferior colliculus neurons to signals with various number of cycles in a pure tone burst (n=1;10;f/1000X50), were estimated. A great majority of neurons were characterized by pronounced frequency selectivity even to signals containing one cycle. Response thresholds mainly depended on the tone frequency; the maximal threshold sensitivity was obtained at the same frequency when tested with 1 or 10/sec sine wave and 50 msec duration tone. Sharpness of the frequency-threshold curve depends both on duration of signal and discharge pattern of the neuron: when the signal duration decreases sharpening of the frequency-threshold is observed in neurons with initial response, while flattening of the frequency-threshold curve is observed in neurons with sustained response.

Animals↗