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G A Ivanitskiĭ

Publications and source records attributed to G A Ivanitskiĭ.

11 recordsLinked to original sources
PubMed1997

[Use of artificial neural networks in recognition of types of thinking by EEG].

Reflection in EEG parameters of the process of solving two types of mental tasks, i.e. spatial-imaginary and verbal-logical, was investigated in nine test-subjects. Mental efforts were found to specify EEG spatiofrequency patterns depending on the task type and subject's identity. These patterns were unique and reproducible enough to enable identification of this or the other type of mental task within several seconds of EEG record. Recognition was executed with the use of an artificial neural network algorithm in order to simultaneously weigh a wealth of signs of a specific EEG pattern. Recognition precision was 85% on the average.

Adult↗
PubMedDate not supplied

[The cortical interactions in short time intervals during the search for verbal associations].

Cortical connectivity was studied in tasks of generating the use of words in comparison with reading aloud the same words. These tasks were used earlier in PET and high-density ERP recording studies, which described both the functional anatomy and time course of involvement of cortical areas in word processing. We developed a new method for studying the synchrony of EEG spectral components within the short time intervals compatible with the duration of particular cognitive operations. The wavelet transform of the ERP records and calculation of correlations between the wavelet curves were used to reveal connections between cortical areas. Three stages of intracortical communications developing over the course of task performance were discovered: between the right and left frontal areas (0-200 ms after the stimulus presentation), between the left frontal and left posterior temporo-parietal areas (250-500 ms), and, finally, between the left temporal and right fronto-centro-temporal areas. These findings are in good agreement with the results of the previous PET and ERP studies and supplement them with the circuitry of cortical information transfer. Also, they suggest some differences in information processing during automated reading and performance of more complicated use-generation task.

Adolescent↗
PubMedDate not supplied

[Selective attention and memory: evoked potentials in visual and auditory verbal competition].

The brain mechanisms of the selective verbal attention were studied using evoked potential (EP) technique. It was shown that the late "cognitive" EP components (400-800 ms) related to memory function were more positive to the words presented via a relevant sensory channel and more negative to irrelevant words. The hypothesis is advanced that words delivered via two competing sensory channels, such as visual and auditory, are perceived, i.e., the subject sees and hears them. However, irrelevant signals are not stored in episodic memory due to the active inhibition of the information transmission to the hippocampal structures.

Adult↗
PubMedDate not supplied

[Dipole models for the sources of late evoked potential components in verbal tasks for intermodal attention and memory in humans].

In this paper we aimed at studying brain structures involved in intermodal attention and memory processes. This was accomplished by dipole modeling of the difference waves of event-related potentials recorded during the performance of verbal tasks and in the control condition. The models were constructed independently from each other for six difference waves obtained by subtracting different experimental conditions. The majority of equivalent sources were located in temporal and frontal areas. The differences in the evoked activity observed between task conditions in the interval from 450 to 850 ms are mainly related to variations in the activity of the hippocampus and adjacent structures.

Acoustic Stimulation↗
PubMedDate not supplied

[Simulation of spontaneous discharge and short-term adaptation in acoustic nerve fibers].

A model for firing of the auditory nerve fibres was carried out on a general purpose digital computer. In the model a noise with small correlation time and with assigned standard deviation (when modeling a spontaneous discharge) or a sum of a noise and a determinated signal (when modeling an elicited discharge) is compared with incremental threshold. When the threshold is exceeded a spike occurs and the threshold is increased. The threshold qualitative properties and quantitative values were chosen in a way to provide the most reliable patterns of spontaneous discharge, according to the literature data obtained from the cat's auditory nerve. When stimulated by tone-bursts the model reveals intrinsic ability of mimicking the phenomena of discharge rate short-term adaptation. Thus according to our model the short-term adaptation is entirely due to the properties of the incremental threshold.

Acoustic Stimulation↗
PubMedDate not supplied

[The disordered organization of the cortical processes in depression].

The study of depressive patients with the method of the EEG mapping revealed some stable differences from the norm. Firstly, in depression there are the disturbances of the definite cortical zones' activation: the right anterior and the left posterior cortical parts are hyperactivated while the left anterior and the right posterior-- relatively inhibited, evidently causing the informational processing disturbances. The important link of these disturbances--the disconnection of the anterior and the posterior cortical regions that could be called "transversal functional blockade". The second feature of the electrical activity of the brain in depression is the absence of the high frequency component of alpha-rhythm, that evidently in normal conditions is connected with the positive emotions mechanisms. The third feature is the difference in arousal reaction in the alpha- and beta-bands frequencies.

Adjustment Disorders↗
PubMedDate not supplied

[The spectral rearrangements of the EEG and the organization of the cortical connections during spatial and verbal thinking].

Solution of spatial and verbal tasks was studied in 43 subjects using the advanced version of the method of intracortical interaction mapping (IIM) and analysis of EEG spectra in short (250 ms) intervals. Comparison between the IIM and coherence methods during solving simple motor tasks revealed some advantages of the IIM for studying of labile cortical connections. Several stages were separated in the process of solution of the mental task in accordance with patterns of cortical connections. The duration of the stages was similar in both kinds of tasks and corresponded to that revealed in psychological experiments. Cortical connections in the theta range were generalized and reflected the level of general tension. This unspecific tension was high for the whole period of the spatial task solution while in the verbal task the tension increased to the stage of decision making. Task-specific patterns were revealed in the beta range. The right parietal and temporal regions were the centers of EEG connections during solution of the spatial task while the left central area was essential for the verbal task solution. The left parietal area was involved in solution of both kinds of tasks. The frequency parameters of connections in the beta range were stable during the spatial task solving, and in the process of verbal task solving the dominant frequency changed after the initial (perception) stage probably due to switching to another thinking mechanism.

Adolescent↗