Putative Trace-Amine Associated Receptor 5 (TAAR5) Agonist α-NETA Increases Electrocorticogram Gamma-Rhythm in Freely Moving Rats.

Cortical gamma rhythm is involved in transmission of information (communication) between brain areas that are believed to be involved in the pathogenesis of cognitive dysfunctions. Trace amines represent a group of endogenous biogenic amines that are known to be involved in modulation of function of classical monoamines, such as dopamine. To evaluate potential modulatory influence of a specific receptor for trace amines Trace Amine-Associated Receptor 5 (TAAR5) on the dopamine system, we used HPLC measurements of dopamine and its metabolites in the mouse striatum following administration of the putative TAAR5 agonist α-NETA. Administration of α-NETA caused significant modulation of dopaminergic system as evidenced by an altered dopamine turnover rate in the striatum. Then, to evaluate potential modulatory influence of TAAR5 on the rat brain gamma rhythm, we investigated the changes of electrocorticogram (ECoG) spectral power in the gamma-frequency range (40-50 Hz) following administration of the putative TAAR5 agonist α-NETA. In addition, we analyzed the changes of spatial synchronization of gamma oscillations of rat ECoG by multichannel recording. Significant complex changes were observed in the ECoG spectrum, including an increase in the spectral power in the ranges of delta (1 Hz), theta (7 Hz), and gamma rhythms (40-50 Hz) after the introduction of α-NETA. Furthermore, a decrease in the spatial synchronization of gamma oscillations of 40-50 Hz and its increase for theta oscillations of 7 Hz were detected after the introduction of α-NETA. In conclusion, putative TAAR5 agonist α-NETA can modulate striatal dopamine transmission and cause significant alterations of gamma rhythm of brain activity in a manner consistent with schizophrenia-related deficits described in humans and experimental animals. These observations suggest a role of TAAR5 in the modulation of cognitive functions affected in brain pathologies.

[SACCADES AND PRESACCADIC SPIKE POTENTIAL DURING THE GAME OF TETRIS].

Saccades and microsaccades were studied during a game of Tetris using the method of EOG. In the experiments 19 players of different skill level were involved. EOG was recorded in monopolar mode with respect to the ear electrodes in 6-points around both eyes to account for the gaze displacement in 8-direction. The game of Tetris was on 3 difficulty levels. It is shown that each saccade on EOG preceded by a sharp negative potential of 10-15 ms or «pre-saccadic peak¼. Its parameters are very stable at the given person, while EOG parameters of themselves saccade vary from their direction. When bipolar registration peak is not detected. The peak amplitude does not depend on the saccade direction, but correlates with saccade amplitude. It is assumed that the peak generators are neuromuscular synapses. Everything else being equal men were characterized by shorter saccades and greater percentage of microsaccades than women. On the middle level of difficulty at the optimal level of attention (but without the stress) are observed smallest saccades. For all players have dominated vertical saccades from the block to the glassful bottom and backward. In the transition from light to hard level for experienced players is increasing the proportion of «extra¼ non-vertical saccades, while the proportion of beginners «extra¼ saccades always relatively high.

[Human traveling wave EEG during voluntary movement of the hand].

The traveling wave trajectories connected with the movements of the right hand were revealed. Above sensomotor cortex 28 electrodes were set as a rectangle--4 rows with 7 electrodes in each one. 2D center-out reaching task was used. The target appeared on the screen edge through the random intervals 0.5-2.5 s equiprobably at the left, on the right, from above or from below. The task was to touch the target with the joystick-operated cursor displacing the cursor in one of the sides from the center to edge. EEG from the target occurrence till cursor contact with it was analyzed. Leading on phase of spontaneous EEG waves in the local area of the left sensomotor cortex and in the centre of back-parietal cortex during cursor movement downwards (the hand with joystick moves to oneself) comparing to rest state and movements in three other directions is revealed. The over time smoothing of data concerning phase alignment reveals hidden constant components in EEG resembling evoked potentials.

[Reproduction of images present in different phases of alpha wave].

It is considered that sensitivity of cortical perceptive mechanisms changes simultaneously with alternation of alpha-rhythm phases and it affects visual recognition accuracy. To verify this statement we detected alternation of alpha-wave phases online for sending stimuli in the middle of increase-phase or in the middle of decrease phase with high precision. 15 healthy volunteers (5 male and 10 female) were observed. They also took tests to measure anxiety, extraversion and neurotism levels. Visual area O2 with maximum amplitude of alpha rhythm was used to control the stimulation. We compared reproduction (by hand drawing) after presenting sample lines in different alpha-wave phases, successfulness during copying of the samples of different lengths was also compared. Most volunteers (14 out of 15) reproduced reduced lines in comparison with samples after stimulation bound to either of two alpha-wave phases. This effect is less prominent during decrease phase (positivation), i.e. lines are drawn longer and match the sample better, than during the increase phase (especially for long-sized samples). This impact of different conditions on task performance is less manifested in volunteers with low psychoemotional stability.

[Eye movement detection with the aid of the oculogram in shifting the gaze].

Eye saccades are accompanied by changes of ocular electric potential. The sign of these changes involves a function of electrode location and eye movement direction while an indicator of the rotation angle is the amplitude. Based on the spatial distribution of the ocular potential one can solve an inverse problem and recover eye movement trajectory to be used for on-line computer control. To achieve this a system has to be able to place a cursor to a point on a screen corresponding to the current gaze direction of the user. We used four electrodes, two inferior and two lateral around the ocular depths. Inferior electrodes were used for estimation of the vertical gaze shift component and the lateral electrodes for estimation of the horizontal component. We detected and processed saccadic unipolar potential changes whose morphology resembles that of the step function. Detection and processing was performed using our proprietary multistage filter applied to the 4-channel data. The output of this filter was used to compute eye rotation parameters. Characteristic potential changes during the spontaneous blinks were identified and excluded from processing. Voluntary winks were used to mimic mouse clicks. In the beginning, our subjects went through a calibration stage during which they had to follow the cursor in eight basic directions. Using the calibration results the inverse problem was solved, i. e. based on the spatial distribution of ocular potential we computed screen position coordinates corresponding to the gaze direction. The presented technique belongs to the class of brain-computer interfaces. In addition, this work led us to a set of interesting observations regarding the characteristic patterns of eye movements. For instance, we found that just prior to a saccade EOG demonstrates short negative potential of 10-15 ms duration. We have also observed that with age the saccade amplitude decreases. Interestingly, when the gaze is shifted to the left, the left eye deviation significantly exceeds that of the right eye but the right shift does not exhibit such an asymmetry. During the diagonal shifts (bottom-right, top-left) the right eye skew exceeds that of the left one and the situation reverses for the two complimentary directions. We have observed no significant differences in eye coordination due to the subject gender.

Lateral inhibition in neural networks and the shape of EEG alpha rhythm waves.

Baseline EEG traces were recorded from the right occipital area with the eyes closed in 15 subjects. Rhythmic stimulation with bright, diffuse flashes of light was applied through the closed eyelids at specific points in the alpha-wave phase (trigger photic stimulation). Ten versions of stimulation were used, with application at different phases for 1 min at each phase. Responses occurring in conditions of stimulation in different phases were compared using the mean alpha wave amplitude in each version and the wave shape in terms of the level of asymmetry of the leading and trailing fronts. When flashes were delivered at the middle of the descending front of the potential (positivization), changes in wave shape were most marked and were very different from those seen in the other nine stimulation phases. This effect was most marked in subjects with low-amplitude alpha rhythms. These results suggest that the individual level of the alpha rhythm in a given subject and the dynamics of the wave shape can be explained by the characteristics of the structure of the system of recurrent-lateral inhibition.

Reflection of the pattern of cortical activation in the phase structure of the human EEG.

A total of 22 healthy subjects in the EEG laboratory and 62 patients in the clinical functional diagnostic unit were studied. Spontaneous EEG recordings were made using the 10-20 scheme relative to combined ear electrodes in the state of rest with the eyes closed and open and during various functional loads. Traces were analyzed by computer animation of the EEG phase structure. The main concept of the method for extracting phase structure was based on not using a single reference lead. Time shifts were measured only between neighboring electrodes, with the result that the oscillations being compared were highly coherent. Time discordance was assessed in terms of the shift in the peak of the cross-correlation function. The results showed that from the point of view of phase structure, the differences between the high-and low-frequency EEG rhythms were purely quantitative. Qualitatively, the properties of the rhythms were identical and were reduced to slow (in the seconds range) oscillations of phase shifts. Low-frequency activity was characterized by large (in absolute terms, msec) phase shifts from electrode to electrode as compared with high-frequency activity. The phase shifts of potentials formed a structure which was overall very similar in different subjects and was reproduced in different leads. The initial appearance of EEG waves was statistically linked with the main sensory projections--the visual (occipital areas), auditory (temporal areas), and somatic (parietal areas), with addition of the frontal areas. Rearrangement of phase leadership in favor of the occipital pole at the expense of both temporal areas was observed on opening the eyes. This appears to depend on the level of sensory influx to this cortical area from the thalamus. It is suggested that the direction of the phase gradient reflects a gradient of cortical current density parallel to the surface. This can be used to locate compact sources lying close to the surface.

[Reflection of cortical activation pattern in the human EEG phase structure].

Investigation was fulfilled on healthy subjects (22) and on outpatients (62). The EEG by the standard scheme as recorded at resting with open and closed eyes and under different functional loads. These records were processed in accordance with the EEC phase structure with the aid of computer animation technology. The main idea of the phase structure technology consists in rejection of one supporting lead. Time shifts were measured only between two neighbouring electrodes, so that the oscillations under comparison were always highly coherent. Time errors were evaluated according to crosscorrelation function maximum shift. The differences between high- and low-frequency EEG rhythms were shown to be only quantitative from the phase structure viewpoint. Qualitatively, the rhythm properties were equal and came to slow (second) phase structure oscillations. Low frequency activity compared to high frequency one was characterized by greater phase shifts from electrode to electrode. Phase shifts of potentials are forming the structure which, as a whole, is very similar in different people and is reproduced in different states. Initial EEG waves appearance is statistical linked with main sensory projections: visual (occiput), auditory (temples) and somatic (parietal region) with addition of frontal region. Redistribution of phase leadership in favor of occipital pole and to both temporal regions when eyes are open is described. It is apparently dependent on the sensory surge level from thalamus to a given cortex region. Phase gradient direction seems to reflect the cortex current density gradient which is parallel to surface. It can be used for localization of compact sources lying near to cortex.

[The indices of EEG spatial synchronization in normal 10- to 12-year-old schoolchildren and in learning difficulties]. / Pokazateli prostranstvennoi sinkhronizatsii EEG u shkol'nikov 10--12 let v norme i pri trudnostiakh obucheniia.

10-12-year-old schoolchildren were divided into three groups: a normal one, a group with psychological problems, and a third one with medical problems. The EEG was recorded at resting and while reading a text. An obviously higher global spatial synchronisation was found in the normal group as compared with the "medical" one. In the "psychological" group, a diffuse hyperresponsiveness was found in the transition state from resting to activity. The above differences seem to be due to a morpho-functional immaturity and a functional insufficiency of two different portions of the brain ascending activating system. Evidently the "medical" group children have an immaturity of the bulbar and midbrain reticular formation, whereas the "psychological" group children have, probably, an immature diencephalic activating system (the thalamus).

[Dependence of human EEG spatial synchronization on the geomagnetic activity on the day of experiment]. / Zavisimost' prostranstvennoi sinkhronnosti EEG cheloveka ot geomagnitnoi aktivnosti v den' opyta.

Spontaneous EEG was registered under different activity conditions in 26 volunteers. The EEG synchronisation parameters were compared with the geomagnetic and solar activity on the day of experiment. A positive correlation of the EEG data with the geomagnetic activity was revealed, being most obvious in the frontal and central areas. A negative correlation between some local EEG synchronisation parameters and different indices of the solar activity, was also revealed. The degree of synchronisation of the spontaneous EEG seems to reflect sensitivity of the human nervous system to the Earth's magnetic field. A stressor response to strong short-term disturbances in the geomagnetic field reveals itself in the form of enhancement of the EEG global synchronisation. A sedative effect of slow magnetic oscillations is locally revealed in the parameters of the EEG synchronisation within the left hemisphere as well as the interhemisphere synchronisation.

[The effect of sex on the spatial synchronization of the EEG]. / Vliianie pola na prostranstvennuiu sinkhronizatsiiu EEG.

The data obtained shows that women are characterised by a significantly larger interindividual variations of the EEG synchronizing than men (except the synchronizing in the left hemisphere). The findings are supposed to be due to a higher level of unspecific cortical activation in men.

[The form of the spontaneous EEG waves under different conditions of mental activity]. / Issledovanie formy voln spontannoi EEG v raznykh usloviiakh umstvennoi deiatel'nosti.

Value of the average level of asymmetry of the EEG waves' fronts (ALA) was shown to decrease in posterior leads and increase in anterior leads during the transition from the rest to mental activity. An inter-hemisphere asymmetry of the ALA was found, the asymmetry having a similar direction for all the pairs of symmetrical leads. Two independent factors are supposed to affect the ALA: the level of the cortex activation and the specifics of information processing by the given hemisphere.

[The mean level of EEG wave asymmetry as a possible correlate of the property of lability of the cerebral hemispheres]. / Srednii uroven' asimmetrii voln EEG kak vozmozhnyi korreliat svoistva labil'nosti polusharii golovnogo mozga.

The human nervous system's lability was studied with the aid of critic fusion frequency (CFF). The CFF was compared with the mean level of asymmetry of the EEG waves' fronts (MLA). The CFF was shown to be a relatively stable individual parameter whose value depended on the value of difference between occipital and frontal areas' MLA and those in the lower frontal areas.

[The reflection of functional differences between the hemispheres in the form of the EEG waves]. / Otrazhenie v forme voln EEG funktsional'nykh razlichii mezhdu polushariiami.

The EEG was recorded in 3 symmetrical sites of the human brain with subsequent calculation of the parameter of mean level of asymmetry (MLA) in the EEG wave fronts. The MLAs were shown to change after functional loads of visual-spatial and verbal-logical types. The MLA seems to be an informative parameter of qualitative specifics of neural processes in the left and right hemispheres.