Interhemispheric phase interactionsbetween high-frequency and low-frequency rhythms of EEG in short timeintervals perception

Interhemispheric phase interaction between high- and low-frequency rhythms ofEEG was investigated in 7 males and 14 females aged from 18 to 26 years old. Duringpreview observation with H. Eysenk's tests, verbal and non-verbal intellect, extraversion-introversion and neuroticism level was determined. Interhemispheric asymmetrywas investigated with using standard tests set for identification dominant hand andspeech-hemisphere. Two modes of observations (reproduction and admeasuring of200 ms and 800 ms time intervals with and without feedback) were provided.In one mode, time intervals were presented as non-verbal stimuli (light square with2 cm side which was presented in the center of monitor screen). In another set, digitalsstimuli (in admeasuring intervals) were used.As a feedback signal, relative reproduction of admeasuring error in percentage ofthe time interval was used. EEG was recorded in sides: Cz, Fz, Pz, F3, F4, C3, C4, P3,P4, T3, T4, T5, T6, O1, O2 under «10-20%» system with 24-canals encephalographanalyzer.Integrated reference electrode was installed on subject's earlaps of left andright ears; earthing electrode was installed on the wrist of the right hand. Phase interactionbetween EEG gamma-frequency and low-frequency bands were estimated with bispectralwavelet analysis and bicoherent function. As integral characteristics of phase interactionlevel between EEG high- and low-rhythms (0,5-30 Hz) were used half-sum ofthis function in the corresponding frequency band. The correlations between these parameterswere estimated with Spearmen's coefficient correlation. To determine the impactof different factors ("gender", "activity type", "activity stage" etc.) on phase interactionwas used repeated measures analysis. This investigations showed that gender, activitytype and activity stage have a significant impact on the phase interaction. It isfound that close phase interconnections between 30-40 Hz gamma-frequency and alpha-,beta-, and tetha- brain activity were the most frequent. Statistically significant correlationsbetween phase interaction level and intelligence quotient, extraversion, neuroticismand interhemispheric asymmetry were found. The result of this research showed that thekind of correlations is completely different from males and females and depends on theactivity type and activity stage. It is proposed that the investigated phase interactioncould be the results of synaptic potentiation as well as distant field interneuronal interactions.

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