[The P300-based brain-computer interface: presentation of the complex "flash + movement" stimuli].

The P300 based brain-computer interface requires the detection of P300 wave of brain event-related potentials. Most of its users learn the BCI control in several minutes and after the short classifier training they can type a text on the computer screen or assemble an image of separate fragments in simple BCI-based video games. Nevertheless, insufficient attractiveness for users and conservative stimuli organization in this BCI may restrict its integration into real information processes control. At the same time initial movement of object (motion-onset stimuli) may be an independent factor that induces P300 wave. In current work we checked the hypothesis that complex "flash + movement" stimuli together with drastic and compact stimuli organization on the computer screen may be much more attractive for user while operating in P300 BCI. In 20 subjects research we showed the effectiveness of our interface. Both accuracy and P300 amplitude were higher for flashing stimuli and complex "flash + movement" stimuli compared to motion-onset stimuli. N200 amplitude was maximal for flashing stimuli, while for "flash + movement" stimuli and motion-onset stimuli it was only a half of it. Similar BCI with complex stimuli may be embedded into compact control systems requiring high level of user attention under impact of negative external effects obstructing the BCI control.

[Dependence N200 and P300 ERPs in P300-based brain-computer interface on the variations of voluntary attention].

Hypothesis about dependence P300 and N200 potentials evoked by flashes of rows and columns of the stimulation matrix on type of the task and voluntary attention was evaluated. We tested three types of the task: 1) just look at target symbol; 2) look at the target symbol, count its flashes and report the amount of flashes after finishing the task; 3) type target symbol in P300-based brain-computer interface (BCI). In 17 subjects research we showed that maximum amplitudes of P300 and N200 ERPs was occurred in the second type of the task ("look at and count flashes"). Also in this type of task we observed most of all cases statistically reliable difference between target and nontarget P300 and N200 ERPs. Lowest amplitudes of ERPs and number of cases of statistically reliable differences between target and nontarget were showed in the first type of the task ("just look at the symbol"). So we assume that succesful working in P300-based BCI doesn't need the maximum amplitudes of the relevent ERPs but most depend on spatiotemporal complex of these potentials.

[The P300 based brain-computer interface: effect of stimulus position in a stimulus train].

The P300 brain-computer interface (BCI) is currently the most efficient BCI. This interface is based on detection of the P300 wave of the brain potentials evoked when a symbol related to the intended input is highlighted. To increase operation speed of the P300 BCI, reduction of the number of stimuli repetitions is needed. This reduction leads to increase of the relative contribution to the input symbol detection from the reaction to the first target stimulus. It is known that the event-related potentials (ERP) to the first stimulus presentations can be different from the ERP to stimuli presented latter. In particular, the amplitude of responses to the first stimulus presentations is often increased, which is beneficial for their recognition by the BCI. However, this effect was not studied within the BCI framework. The current study examined the ERP obtained from healthy participants (n = 14) in the standard P300 BCI paradigm using 10 trials, as well as in the modified P300 BCI with stimuli presented on moving objects in triple-trial (n = 6) and single-trial (n = 6) stimulation modes. Increased ERP amplitude was observed in response to the first target stimuli in both conditions, as well as in the single-trial mode comparing to triple-trial. We discuss the prospects of using the specific features of the ERP to first stimuli and the single-trial ERP for optimizing the high-speed modes in the P300 BCIs.

[Late negativity in visual event-related potentials in humans to changes in topology of simple nonverbal stimuli].

Late negativity arising in ERP in response to a semantic mismatch of consistently presented stimuli is usually considered to be related with verbal or symbolic representation of stimulus during perception. It is shown in this work that the late negativity typical of the semantic mismatch develops even in the context of non-symbolic and nonverbal, for example, four-point stimulus compositions which differ only in typology or angular size. Attention distraction from trial stimuli completely eliminates the effect of the late negativity. It is suggested that the brain finds semantic and formal (physical) descriptions for any stimulus composition. This phenomenon is reflected in the N400 amplitude depending on the attention volume to the stimuli per se.

[The multipleparameter combinatory analysis of EEG rhythms in norm and at schizophrenia].

On the base of EEG records of 38 healthy subjects and 17 schizophrenic patients the statistical structural analysis of 176 elementary characteristics in all 11 spectral ranges for each of 4 experimental conditions was carried out, employing "Kora-n" recognition algorithm, adopted for EEG analysis by Kaplan. The list of characteristics with a minimal error revealed statistically significant differences between spectral power of delta- and theta-ranges in healthy subjects and schizophrenic patients. Spectral power of these slow rhythms was always higher in the formers then in the latter. As a whole, in schizophrenic patients the decrease of delta-rhythm spectral power in the lower frontal area of right hemisphere and theta-rhythm - in the lower temporal area of left hemisphere most frequently is observed. These results are in agreement with hypofrontality and hypotemporality characteristic of schizophrenic patients and testify to the lack of "fundamental" brain base of cognitive functions. These facts are evidently connected with the significant neurochemical disturbances taking place in schizophrenia.

[Functional variability of the autocorrelation structure of the EEG].

On an example of records EEG of 39 healthy subjects, the quantitative analysis of variability of the autocorrelation structure of one-second EEG segments was carried out on the basis of comparison of structural functions constructed for these segments. It was shown that more than 30% of cases, statistically significant sifferences were observed between the structural functions of successive one-second EEG segments shifted by 1-3 s, as compared to surrogate EEGs formed with the tangled random sequence of count points. On the basis of the obtained data, the index of nonstationarity of the EEG autocorrelation structure was proposed. This index can be used for the objective quantitative evaluation of the functional states of the human brain.

[Classification of the adolescent EEG by the spectral and segmental characteristics for normals].

The 16-channel EEG records of 45 adolescents with schizophrenia and 39 healthy adolescents were subjected to statistical combinatorial analysis of 160 elementary EEG characteristics (6 spectral and 4 segmental EEG characteristics for a channel). Employing pattern recognition algorithm "Kora-n", a list of 37 combined EEG patterns was compiled. This list characterized with a minimal error the EEG of healthy adolescents in such a way that none of these characters featured the EEG of adolescents with schizophrenia. Analysis of this list of EEG characteristics suggests that the contrast between EEG of healthy and ill adolescents is the sharpest in the F4, Cz, T3 and O1 derivations. Compared to EEG samples of schizophrenic subjects, EEGs of healthy subjects exhibit lower levels of delta and theta activity mainly in the frontal and temporal regions of the cortex and higher level of alpha activity predominantly in the occipital region. Applicability of the list of EEG patterns for diagnostics of schizophrenia-type disorders of adolescents is discussed.

[Segmental structure of the EEG alpha activity in adolescents with disorders of schizophrenic spectrum].

The EEG records of 39 healthy adolescents and 45 age-matched schizophrenic patients were analyzed. The broad-band EEG spectral analysis and segmental analysis of the alpha-activity revealed significant differences between the groups. Schizophrenics differed in a decreased spectral power for the alpha2 and betal frequency bands and increased power for the delta and theta bands. Also, in schizophrenic adolescents, quasi-stationary alpha-rhythm segments were longer, and within-segmental EEG amplitudes were higher than in the healthy subjects; the amplitude variability and the steepness of transitions between neighbor segments were increased. The results of the EEG segmental analysis suggest a disintegration of local cortical neuronal ensembles in schizophrenia.

[The nonstability of the EEG: a methodological and experimental analysis]. / Nestatsionarnost' EEG: metodologicheskii i éksperimental'nyi analiz.

Theoretical, methodological and methodical aspects on nonstationary EEGs, that is, EEGs whose patterns undergo changes with time are reviewed. The piecewise description of the EEG is confirmed on the base of the own data and results of another investigators. It is analysed the basic approach to statistical evaluation of nonstationary EEGs in the terms of quasi-stationary segments. The special attention is devoted tho the data of segmental organization of the bioelectrical field of the cortex. Taking into consideration new experimental data concerning the time consistency of the segmental descriptions of regional EEGs it is suggested conception of "operational synchrony" as a form of discretial cooperation of cortex process. The theoretical explanations of the phenomenology for piecewise functioning of neuron nets are discussed.

[The variability of the heart rhythm and the nature of the feedback as a result of operator activity in man]. / Variabel'nost' ritma serdtsa i kharakter obratnoi sviazi po rezul'tatu operatorskoi deiatel'nosti u cheloveka.

In a memory task which required sustained attention, the positive or negative emotional state of an operator was created by introduction of two different types of feedback in accordance with the number of correct or wrong solutions. Standard and original indices were used for evaluation of the short-term variability of the heart rate (HRV) during performance. Changes in the HRV were observed only in the periods of performance with the failure type of the feedback. These changes reflected stabilization of heart bit-to-bit intervals. The original index of the fast HRV turned to be the most sensitive for testing HRV changes. Human autonomic reactions of such a kind during operator-like activity are known as a predictor for the functional state of dissatisfaction. This confirms the practical importance of application of the HRV indices for testing the ergonomic properties of the systems which control the operator-computer interaction.

[Dynamic properties of segmental characteristics of EEG alpha activity in rest conditions and during cognitive tasks]. / Dinamika segmentnykh kharakteristik al'fa-aktivnosti EEG cheloveka v pokoe i pri kognitivnykh nagruzkakh.

Segmental structure of the alpha activity of human EEG was studied in the state of rest and during arithmetical task performance with mono- and binaural listening of task instruction and binaural listening of music. The amplitude, duration, amplitude variability and steepness of between-segment transitions were calculated as segmental characteristics. It was shown that all of these characteristics are sensitive to the cognitive tests but the degree of this sensitivity depends on the cortex area and type of the cognitive task. Most pronounced changes in the segmental characteristics were observed during arithmetic task with left-side instruction presentation and minimal changes were seen during binaural listening of music.

[Spatial synchronization of the segmental EEG in humans]. / Prostranstvennaia sinkhronnost' segmentnoi struktury EEG cheloveka.

Topographic features of spatial synchronization of sharp changes, or rapid transition processes (RTP), were studied in human EEG recorded from longitudinal and transversal electrode arrays. A new algorithm, the EEG Threshold Scanning, was proposed for the detection of the RTP. Synchronization of the RTP was estimated by Operational Synchrony Index (OSI) based on the difference between the actual and stochastic frequency of RTP coincidence in a pair of EEG channels. The relationship between the OSI and interelectrode distance was not monotonous. The OSI depended also on the extent of morpho-functional similarity between two cortical areas. Similar results were obtained for crosscorrelation calculated for the same pairs of the EEG derivations. The existence of dynamic spatial modules which incorporate different brain areas by complementary stabilization of their functional states is discussed.

[Topographic mapping of the process of synchronizing moments of sharp changes in the human multichannel EEG]. / Topograficheskoe kartirovanie protsessa sinkhronizatsii momentov rezkikh perestroek v mul'tikanal'noi EEG u cheloveka.

Techniques of evaluation were studied of the EEG synchronization between different EEG derivations in humans. It was shown that the pattern of cortical cooperativity constructed on the basis of classical EEG crosscorrelation and coherence could be substantially supplemented with estimations of coincidences of the moments of sharp changes (MSC) in multichannel EEG recording (the so called "operational synchronization"). The multichannel EEG was recorded in humans during memory task performance. A non-parametric technique was developed on the basis of the family of Kolmogorov-Smirnov's statistics for revealing the MSC in separate EEG realizations and subsequent spatial-temporal mapping of the MSC coincidences in different derivations of the multichannel EEG. It was shown that such maps markedly change depending on the current cognitive activity of the subjects. An attempt was made to interpret the estimations of the frequency and operational synchronization of multichannel human EEG.

[The temporal consistency of phasic conversions in the basic frequency components of the EEG]. / Vremennáia soglasovannost' fazicheskikh perestroek osnovnykh chastotnykh komponentov EEG.

The study is dedicated to the problem of piecewise description of stationary segments of the EEG basic rhythms. Temporal consistency was studied of the moments of sharp changes in characteristics of the individual basic EEG frequency components within the same realization. In 6 human subjects (in the state of quiet wakefulness with eyes closed) a rather high number was shown of nonrandom paired coincidences of the moments of sharp changes in characteristics of 5 EEG basic rhythms. Such between-component consistency was most expressed for a combination of alpha2-beta1 frequency ranges. The main topographic feature of this phenomenon was a substantial (2-4 times) increase in the indices of between-frequency consistency from the occipital to frontal areas. The character of changes in these indices was closely the same in 10 paired combinations of the EEG frequency bands, at least in the frontal and central derivations. The obtained results suggest the existence of a special operational synchrony of the EEG basic rhythms. In contrast to the classical phase-frequency synchronization, this kind of synchrony reflects the temporal consistency of quasistationary modes of brain activity.

[The adaptive classification of the dynamic spectral patterns in the human EEG]. / Adaptivnaia klassifikatsiia dinamicheskikh spektral'nykh patternov EEG cheloveka.

The classification technique of single spectra based on a matrix of intercorrelation between these spectra and the fixed set of standard spectral patterns (SP) has been put forward. Including in the classification technique a special procedure for automatic adaptation of the standard SP to given EEG records makes it possible to reduce the number of unclassified single spectra to a minimum (6-10%), which we can ignore during comparative analysis of the EEG classification profiles. Using the universal set of standard SP makes it possible to compare the results of classification of different EEG records. The results of the analysis of classification profiles of human multichannel EEG during performance of the memory task on perception of visual images are described in the paper. It has been shown that both the total EEG reorganization associated with the alpha rhythm blockade during eyes opening and less noticeable EEG shifts accompanying changes in the stages of cognitive activity are underlain by a rather differentiated transformations of relative contributions of each type of the SP into the total power spectrum. It has been revealed that a relatively small part (15-20%) of the elementary EEG segments participates in the reorganization of the EEG classification profile.

[A nootropic adrenocorticotropin analog 4-10-semax (l5 years experience in its design and study)]. / Nootropnyi analog adrenokortikotropina 4-10-semaks (15-letnii opyt razrabotki i izucheniia).

Semax is one of the rare analogues of regulatory peptides which underwent all stages from fundamental investigations to practical usage. It has been demonstrated that this peptide is capable to stimulate operative memory and attention, to increase resistance to hypoxia and to improve brain circulation in experimental animals and human beings over prolonged period (20-24 h after intranasal administration in doses 0.015-0.050 mg/kg). Semax significantly improves memory and attention in healthy men under extreme conditions of activities. Moreover at present semax is successfully used in treatment of patients with different diseases of CNS. In the majority of cases the peptide exhibited positive effects and in no case it produced negative side actions or complications connected with its administration. There is good reason to believe that medical potentialities of semax have not been exhausted and in future new possibilities of its usage will be revealed.

[An electroencephalographic analysis of the anti-ischemic properties of amiridin]. / Elektroéntsefalograficheskii analiz antiishemicheskikh svoistv amiridina.

Amiridine in an oral dose of 40 mg was shown to lead to the disappearance of EEC signs indicating transient hyperventilation ischemia during EEG testing of 15 healthy males. The possible mechanisms of central action of amiridine are discussed in the paper.

[The effect of amiridin on the spectral characteristics of the human EEG]. / Vliianie amiridina na spektral'nye kharakteristiki EEG cheloveka.

EEG testing of 28 healthy males showed that amiridine (two tablets, each 20 mg, orally at a 45-min interval) significantly enhanced alpha stability and spectral power and decreased the stability of delta activity as compared to placebo. These effects were more pronounced in the left hemisphere at rest and in the right hemisphere during mnestic activity. The perspectives of clinical application of amiridine as an antiamnestic drug are discussed in the paper.

[Rhythmic activity of the endbrain in the carp evoked by adequate visual stimulation]. / Ritmicheskaia aktivnost' konechnogo mozga u karpa, vyzvannaia adekvatnoi zritel'noi stimuliatsiei.

In acute experiments on immobilized carps, under dark adaptation conditions, studies have been made on the electrical activity of the telencephalon and midbrain tectum. It was found that in the latter photostimulation evokes local rhythmic activity which includes fast (30-50 Hz) phasic (200-300 ms) and slow (8-14 Hz) tonic (up to 3-4 s) components. High rhythm of this activity may be observed only in "healthy" preparations, coinciding with on-rhythm in the midbrain tectum. Low rhythm does not depend on the presence of rhythmic activity in the tectum. Various aspects of the development of the thalamo-telencephalic system in vertebrates are discussed.

[Dynamic characteristics of element-by-element reproduction of visual matrix images: phenomenology and pharmaco-testing]. / Dinamicheskie kharakteristiki poélementnogo vosproizvedeniia zritel'nykh matrichnykh obrazov: fenomenologiia i farmakotestirovanie.

An outfit "Mnemotest" was employed to examine some regularities of the operative memory of man. The dynamic characteristics are provided of reproduction-storage of the elements of visual matrix images: the curves of "fading" and the "reproduction tempo". It has been shown that oral administration in therapeutic doses of the psychostimulant sydnocarb optimizes the mnemonic processes. Under different conditions the drug either increases the "reproduction tempo" or minimizes the rate of the "fading" of the mnemonic trace.