Correlation between Cognitive Performance and Interhemispheric Asymmetry of EEG Alpha Rhythm during Lateralized Presentation of Visual Information against the Background of Optical Stimulation

The effect of lateralized optical stimulation with a frequency of 10 Hz on the effectiveness of cognitive task performance (n-back test) was studied in 33 healthy subjects (right-handed men). Test visual information was presented to the right or left visual hemifield under normal conditions and against the background of optical stimulation with a frequency of 10 Hz. The absolute values of the spectral power of the high (10-13 Hz) subrange of alpha-rhythm of EEG (SPα2) were calculated. When test information was sent to the right hemisphere against the background of stimulation, an increase in task performance was revealed in subjects with low SPα2. This was accompanied by an increase in SPα2 in some cortical areas of the contralateral (left) hemisphere and, as a result, an increase in left-side dominance of SPα2. The findings indicate the possibility of using lateralized optical stimulation to improve cognitive task performance, in particular, by changing the interhemispheric asymmetry of the EEG alpha2-rhythm.

Analysis of Endogenous Spectral Power of EEG Alpha-Range Biopotentials during Mnestic Activity under Conditions of Rhythmically Organized Optical Stimulation

We studied the effect of optical stimulation (10 Hz) on the effectiveness of mnestic activity in the n-back task in healthy subjects (n=32). EEG was recorded at all stages of the examination. The absolute values of the spectral power of the 10 Hz frequency (μV2) of the alpha range were calculated. According to the results of the test without optical stimulation, the examinees were divided into groups with high (group 1) and low (group 2) task performance. In the initial state, the spectral power of 10 Hz was significantly higher in group 1 subjects. Under conditions of screen flickering, the results became poorer in group 1 and better in group 2 in comparison with the results under normal conditions. These changes were accompanied by an increase in the spectral power of 10 Hz only in group 2 subjects. These findings can provide the basis for the development of practical recommendations for improving the mnestic functions in patients with consideration for the individual characteristics of their initial EEG.

[Dynamics of EEG Alpha-Activity and Heart Rate Variability in Subjects Performing Cognitive Tests]

Changes in the power and coherence of α-activity and heart rate variability (HRV) were studied in students with different performance levels in logical tasks. In those students who reached high scores in the cognitive tests, we observed higher lability of α-activity and HRV; the values and their ratios varied among the stages of intellectual activity. In these subjects, a decrease in the spectral power of α-band was more pronounced than in other groups. We also observed changes in the interhemispheric coherence and in the structure of coherent interactions in the α-range at different stages of task performance. In contrast, the number and structure of coherent interactions in individuals who showed lower results did not significantly vary at different stages of task performance. As compared with this group, the students with higher test results showed a more pronounced decrease in the total spectral power (TP) and an increase in the low frequency/high frequency (LF/HF) ratio which returned to the initial level after the end of the tests. In students with better results in these cognitive tests, the dynamics of RRNN, TP, HF, and LF/H F during task performance correlated with the dynamics of interhemispherical α-band coherence.