[Evaluation by humans of signals modulating different sound movement directions and particulars of perception of such signals in patients with temporal epilepsy].

In patients with epileptic lesions in the hippocampus as well as in the temporal lobe and hippocampus simultaneously, studies were made on the perception of sound signals imitating sound source movement. It was established that hippocampal lesion results in disturbance of estimation of sound spatial characteristics which manifests in a change accuracy of localization and shortening of subjective sound image movement trajectory. Maximum disturbances of localization function are observed during lesions of hippocampus and temporal lobe. Possible neurophysiological mechanism underling observed disturbances are considered.

[Event-related potentials of human brain in spatial hearing].

The review presents the data concerning auditory event-related potentials and their "mismatch negativity" component under conditions of stationary and moving sound source localization. Both free-field and dichotic experimental conditions are considered. The interhemispheric asymmetry of the brain responses elicited by the sound sources of various spatial properties is also discussed.

[About functional evolution of peripheral part of the auditory system].

Functional evolution of the peripheral part of the auditory system is considered. The key point of the appearance of a possibility of analysis of sound waves is formation in the course of evolution of cells with protoplasmic processes (sensillae)--the hair cells--that are transformed into auditory receptors. The fundamental moment is the emergence in evolution of the specialized ionic medium (endolymph) surrounding the auditory receptors. This medium is necessary for generation of receptor potential due to mechanical deformations of the auditory receptor. The characteristic feature of functional evolution of the peripheral part of the auditory system is the many-time repetition in the course of evolution of the main devices to detect and to distinguish sounds. This indicates recapitulation in evolution not only of the central parts of the brain (including central regions of the auditory system), but also of its peripheral part.

[The cat acoustic cortex response to the signal localised signs under conditions of electrical stimulation of the acoustic nerve and sound stimulation].

The mechanisms underlying acoustic capacity to localize the sound source in horizontal plane were studied. The results obtained are discussed from the aspect of existing ideas of the mechanisms providing the localization acoustic capacities in natural way of stimulation in neuronal activity of the acoustic centres. The data obtained are also considered from the viewpoint of a possible considerable improvement of deaf people's spatial orientation with the aid of bilateral implanted cochlear implants.

[Discrimination of the dynamic properties of sound source spatial location in humans (electrophysiology and psychophysics)].

The spatial resolution of human auditory system has been studied while the localization of sound source has been changed according to the different temporal patterns of interaural time delay. Two experimental procedures have been run in the same group of subjects: psychophysical procedure (the transformed staircase method) and electrophysiological one (which requires recording of mismatch negativity, the auditory evoked response component). It has been established that 1) the magnitude of the mismatch negativity reflects the extent of spatial deviance of the sound source 2) the mismatch negativity is elicited even at minimal (20 micros) interaural time delays under both temporal patterns (abrupt azimuth change and gradual sound movement at various velocities) 3) the abrupt change of the sound source azimuth results in greater mismatch negativity than the gradual sound movement does, if the interaural time delay exceeds 40 micros 4) the discrimination threshold values of the interaural delay obtained in the psychophysical procedure are greater than the minimal interaural delays that elicit the mismatch negativity, with the exception of the expert listeners who has shown no significant difference.

[Localization of virtual stimuli moving in the median plane by listeners of different age].

Capability for identification of direction of movement of sound images (upward or downward) was studied in listeners of two age groups: 19- 27-year-old (11 subjects) and 55- 73-year-old (9 subjects). Various sound models of movement in the median plane were used as stimuli. Initially, a model of movement was developed based on filtration of broadband noise pulses by sets of non-individualized. i. e., measured in other listeners, head-related transfer functions. These functions corresponded to consecutive positions of the sound sources with the 5.6 degrees step between the space points with coordinates of elevation from -45 degrees to 45 degrees. The signals generated on the basis of transfer function sets of 23 subjects were distinguished by regulatory and value of the spectral minimum shift as well as by dynamic changes of the spectral maximum. Then the dynamic changes typical on non-individual sound images were used to create synthetic models. In these models, movement of sound images in the median plane was simulated either by a regular shift of the spectral minimum in broadband noise pulses or by a combination of the spectral minimum shift with a simultaneous change of the spectral maximum width and power. The obtained data have shown that young listeners with the high capability for vertical localization could identify direction of the sound image movement based on displacement of the spectral minimum in the broadband noise. For identification of direction of the sound image movement, the younger listeners with poor capabilities for vertical localization and the older listeners used dynamic changes of the signal power, which were connected mainly with the spectral maximum range.

[Inertial processes in the auditory system during localization of moving sound sources].

The significant role of inertial features of the auditory system in localization of moving sound sources is presented. This inertia requires some time of observation about the movement in space of the auditory signals. Slower time of estimation of the localizing features of the moving sound source (as comparing with the unmoving one) is followed by the appearance of new important possibility of the auditory system, namely in perception and analysis of the parameters of moving sound sources. Meanwhile these inertial features are manifested by another significant change in the activity of the auditory system. After the cessation of the auditory signals we observed some aftereffects which manifested that the subjective perceived trajectory of the moving sound source is lengthening toward the direction of the existing movement even when the auditory signal is switched off. Stated above can serve as an evidence of presence in the auditory system some predictive possibilities concerning the direction of moving sound sources. This feature is essential from biological point of view for an adequate organisation of behaviour of the subjects.

[Perception of short musical fragments by hypomaniac patients].

Emotional assessment of short fragments from pieces of chamber music was studied in patients in steady elated mood (hypomaniac). Six fragments, assessed by healthy subjects as emotionally positive, neutral or negative were used. The examined subjects were shown to be capable for an emotional assessment of the musical fragments. The most pronounced difference of the examined patients from healthy subjects and depressive patients examined earlier was the predominance of neutral assessments in hypomaniacs.

[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.

[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.

[Role of phasic changes in sound signal in localization of auditory image]. / Rol' fazovykh izmenenii v zvukovom signale pri lokalizatsii zvukovogo obraza.

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.