Wavelet analysis and its application in investigation of brain potentials during verbal task solving

The components of event-related brain potentials during verbal tasks were investigated with the help of a new method ?? wavelet analysis. Using this method, in 415 ms from the beginning of the stimulus, maximum values of the higher frequency components were revealed in the left parietal zone. During repetition of a verbal task, a tendency to a decrease in amplitude values of the higher frequency components was observed.     

The mapping of brain biopotentials in patients with the depressive syndrome

By means of mapping method a study of spatial distribution of biopotentials was conducted (by alpha-rhythm power and by asymmetry of its energy). It is shown that in patients with depressive syndrome within maniac-depressive psychosis and schizophrenia main neurophysiological properties are paradoxical alpha-rhythm reaction in the frontal cortical regions in response to eyes opening, hyperactivation of the posterior areas of the left hemisphere and also dissociation between activation level of the anterior and posterior regions of the hemisphere, creating the picture of "transversal functional block". After the séance of electrostimulation the "block" disappeared both by alpha-rhythm power parameter and by the parameter of its energy asymmetry; and the activation of the left hemisphere sharply decreased being accompanied by improvement of clinic state of patients.     

The intercentral relations of the biopotentials in the rabbit brain during the creation of a blinking dominant]

On rabbits in chronic experiment intercentral relations were studied of biopotentials of the sensorimotor cortical zone (blinking presentation in the cortex), VPM of the thalamus and motor nucleus of the oculomotor nerve at formation of blinking dominant created by serial stimulation of one eye by air jet. By the method of spectral-correlation analysis an increase was revealed of spectrum power and increase of COG of the potentials in delta-range in the structures connected with blinking function of the stimulated eye. At transition of the dominant focus to the inhibitory state and activation of the symmetrical centre of the other eye, in centers constellation of this induced focus a reconstruction of the electrical processes took place typical for the dominant.     

Motivation effect on power changes in the brain biopotentials in the figurative and verbal creativity tasks

Effect of extrinsic motivation stimulating the most original problem solving during verbal and figurative divergent thinking was studied by EEG mapping. The righthanded university students (27 males and 26 females) participated in the experiments. An instruction "to create the most original solution" as compared to condition with an instruction "to create any solution" induced an increase in the baseline power of the alpha 1 and alpha 2 rhythms most pronounced in the posterior cortex. Task-related desynchronization of the alpha rhythms was higher but the beta-2 synchronization was lower after the former than after the latter instruction. Differences in the asymmetry of the alpha 1 and alpha 2 rhythms in the parietal and temporal regions of hemispheres suggested the right hemisphere dominance in intrinsic alertness and evoked activation related to divergent thinking. The findings were common and gender-independent in both figurative and verbal tasks suggesting a generalized influence of extrinsic motivation on creative activity.     

Spatial synchronization of rabbit brain biopotentials upon repeated electrical stimulation of the cortex]

A study was made on 23 rabbits of the degree of spatial synchronization in response to repeated electrical stimulations of one or simultaneously two cortical areas: the sensorimotor or visual, or simultaneously the sensorimotor and visual, or sensorimotor and precentral respectively. Enhancement of the synchronization induced by the stimulation, globally spread over the entire cortex and was followed by its decrease. However, in the two directly stimulated areas of the cortex, the similarity of bioelectrical oscillations persisted for a long time, which testifies to the establishment of selective relations between them.     

Analysis of probabilistic characteristics of brain biopotentials in healthy humans using electronic computer technology]

Results are given of determination by means of a Minsk-22 electronic computer of the probabilistic characteristics and correlation coefficients for some parameters of the background EEG (frontal-occipital records) in a group of healthy subjects. The parameters studied (the number and amplitude of alpha- and other waves) are subject to the normal law of distribution of random values. A probabilistic model of background EEG has been plotted. Correlations between the factors of the statistic model of background EEG have been studied. The results presented in the paper may prove useful in studying the EEG characteristics and the functional state of the brain.     

The emotional counting Stroop: a task for assessing emotional interference during brain imaging

The emotional counting Stroop (ecStroop) is an emotional variant of the counting Stroop. Both of these tasks require a motor response instead of a spoken response for the purpose of minimizing head movement during functional MRI (fMRI). During this task, subjects report, by button press, the number of words (1-4) that appear on a screen, regardless of word meaning. Neutral word-control trials contain common words (e.g., 'cabinet' written three times), while interference trials contain emotional words (e.g., 'murder' written three times). The degree to which this task represents a true 'Stroop' interference task, in the sense that emotional words will increase motor-response times compared with neutral words, depends upon the subjects of the study and the words that are presented. Much research on the emotional Stroop task demonstrates that interference effects are observed in psychopathological groups in response to words that are specific to their disorder, and in normal subjects when the words are related to current concerns endorsed by them. The ecStroop task described here will produce reaction time-interference effects that are comparable to the traditional color-naming emotional Stroop. This protocol can be completed in approximately 20 min per subject. The protocol described here employs neutral words and emotional words that include general-negative words, as well as words specific to combat-related trauma. However, this protocol is amenable to any emotional word lists.     

The effect of masking in the human subject on the solving of a visual-spatial task

Images of two fragments of regular geometrical figures (square, triangle etc.) have been presented to 58 healthy persons successively with intervals of 20, 80, 120 and 380 ms. The subject must compare these fragments mentally, decide whether they form the standard figure and press a button by the right or left hand according to the instruction. At presentation of both fragments in one visual field, left or right, the number of correct responses is greater when they form the figure. The greater the interstimulus intervals, the greater the number of correct responses to stimuli forming and not forming the standard figure. At presentation of fragments in different visual fields, the number of correct decisions is the same, independently from forming the standard figure. The reaction time is shorter when exposing fragments forming the figure, independently from the way of their presentation; with prolongation of interstimulus intervals the reaction time decreases in all cases. The number of correct decisions is greater and the reaction time is shorter when the stimuli are presented in different visual fields.     

The reflection of emotional tension in the spatial synchronization of the biopotentials in the human brain

In organization of spatial synchronization of bioelectrical activity of the cerebral cortex emotions can play both the role of intensifier and disorganizer of this process. Emotions raise the level of spatial synchronization in situation of active work and may decrease initial background values of synchronization if they organize passive-defensive state.     

The effect of electric stimulation of several zones of the brain on verbal memory in humans]

Investigations of patients with implanted in intracerebral electrodes have shown that within some subcortical structures there exist neuronal-glial populations in which the dynamics of their functional state, according to the results of local recording of slow processes (oxygen tension, local blood flow, impedance), clearly correlates with the correct performance of the tests on operative memory. Electrical stimulation of some of the zones significantly changes the volume of operative memory and influences the general state and higher psychic functions in the patients. The result of electrical stimulation of the brain is determined by the role of different zones in the mnestic act and by the stage at which the stimulation is performed. The role of the cerebral zones is discussed in which the change of the functional state correlated with errors in tests reproduction, the detectors of errors in securing human memory.     

Changes in the power and coherence spectra of the EEG rhythmic components during solution of a verbal creative task of overcoming a stereotype

Changes in EEG power and coherence were analyzed in 117 subjects during the performance of the creative task of finishing well-known proverbs in a new way, so as to change, if possible, their meaning, and the noncreative task of recalling the original (well-known) version of the end of each proverb. A characteristic feature of the creative task was that proverbs and sayings are stereotypes fixed in a memory matrix. During the task performance, the EEG was recorded in 19 derivations according to the international 10–20 system. Performance of the creative task was accompanied by a highly significant and reproducible increase in the power of the γ and β₂ EEG frequency bands, as well as a less pronounced decrease in the power of the ? band in the central and parietoccipital cortical areas. In addition, the performance of the creative task was also characterized by an increase in the EEG coherence in the α₂, β₂, and γ bands. No gender-related differences were found in the patterns of EEG changes.