Yu.G. Kalinnikova
PhD, Associate Professor E.S. Inozemtseva
Professor, Dr.Sc.Psych. E.V. Galazhinskiy
PhD D.Yu. Balanev
Professor, Dr.Med. L.V. Kapilevich
National Research Tomsk State University, Tomsk

Keywords: coherence, rhythm and tempo structure, aerobics, electroencephalographic indices, EEG rhythms.

Introduction

Cognitive functions of cerebral cortex are known to manifest themselves in the electric activity being synchronized in different frequency bands, the phenomena being indicative of activation of the control mechanism that regulates oscillations in the cortical networks. The synchronization patterns may be characteristic of functional correlation disorders in the cortical networks [4].The EEG coherence integrated functionality indices include the correlation magnitude or similarity index and phase spectrum index that is characteristic of how synchronized the neural oscillations or how delayed the EEG coherent oscillations in the cortex region subject to the study are [3].

Studies of the rhythmic musical auditory stimulation effects on the key indices of the cortical bioelectrical activity may give important information on how beneficial for the education individualization initiatives or for improvement of the training effects of aerobic exercises these effects may be [1, 2].

Objective of the study was to explore the effects of physical loads and auditory stimulation by music of varying rhythm and tempo on the intra-hemispheric EEG coherence rates.

Methods and organisation of the study

Subject to the study were 36 young women of 17-20 years of age. We used “Neuron-Spectrum” EEG Integrated Unit (made by Neurosoft Research and Production Association based in Ivanovo, Russia) for the EEG coherence measurements. Electroencephalograms were recorded using a monopole scheme in the following leads: F3, F4, С3, C4, P3, P4, O1 and O2 in the “10-20%” format. Reference electrode was fixed on the left and right earlobes of the subject, and the ground electrode was placed on the right hand wrist.

EEG signals were recorded prior to the physical loads and after the aerobic exercises stimulated by music of varying rhythm-and-tempo structure (RTS) classified as follows: RTS 1 of 115-125 beats per minute (bpm); RTS 2 of 125-140 bpm; and RTS 3 of 140-160 bpm; with the stimulation effects lasting for 20-25 minutes.

The electroencephalograms were recorded in the functionality tests designed as follows:

1. Background EEG record during eyes-closed rest for 1 minute;
2. Auditory stimulation by 115–125 bmp RTS music for 1 minute (Audio 1);
3. Background EEG record following the above auditory stimulation by 115–125 bmp RTS music for 1 minute (Background 1);
4. Auditory stimulation by 125-140 bmp RTS music for 1 minute (Audio 2);
5. Background EEG record following the above auditory stimulation by 125-140 bmp RTS music for 1 minute (Background 2);
6. Auditory stimulation by 140-160 bmp RTS music for 1 minute (Audio 3); and
7. Background EEG record following the above auditory stimulation by 140-160 bmp RTS music for 1 minute (Background 3);

Study results and discussion

Auditory stimulation by the rated rhythmic music in quiescent state was found to evoke growth of frontal alpha EEG coherence (see Table 1) with notably higher response in the left cortical hemisphere, and with the dominant frequency of the coherent rhythms showing an increase. Physical loads were found to evoke reduction of the coherence indices in every frequency range, with the highest effect noted in the 125-140 bpm stimulation tests. Auditory stimulation by RTS 1 rated music rhythms was found to induce growth of the coherence index above the starting level; and after RTS 2 and RTS 3 the coherence was also found to grow, but not that high.

Table 1. Alpha-rhythm coherence rates in the frontal and occipital leads

The auditory stimulation by the RTS music was found to cause no influence on the alpha-rhythm coherence rate prior to the loads. After the auditory stimulation by the RTS music of 115-125 bmp and 125-140 bpm, the alpha-rhythm coherence rate was found to decrease. The auditory stimulation by the RTS 1 and RTS 2 music after the workloads was found to trigger growth of the coherence rate, although it was still lower than the background values.

The theta activity variation patterns with auditory stimulation by rhythmic music were found to be much similar to the above (see Table 2). All three RTS musical stimulations were found to evoke growth of coherence rate both in the frontal and occipital leads. The physical loads were found to reduce the coherence rate, with the effect being particularly expressed in the RTS 2 and RTS 3 stimulation tests. The auditory stimulation by RTS 1 music after the loads was found to initiate the highest growth of the coherence rate, whilst the similar effects following the RTS 2 and RTS 3 musical stimulation tests were found to be notably less expressed.

Table 2. Theta rhythm coherence rates in the frontal and occipital leads

Conclusions

Findings of the study demonstrate that the passive-state auditory stimulation by music of varied RTS compared to the physical loads with auditory stimulation by the same music cause the opposite effects on the cortical bioelectrical activity synchronization patterns. The passive-state auditory stimulation was found to facilitate de-synchronization and reduce the cortical functional abilities; whilst the active rhythmical physical loads stimulated by the same RTS music help synchronize the cortical electric activity and thereby increase the functional activity.

The above findings give reasons to assume that the potential mechanisms of specific influences of different physical loads on the cognitive functions are largely based on cortical bioelectric activity patterns with different coherence rates being formed in the process. The coherence analysis, therefore, may be beneficial for assessments of interrelations between the physical and cognitive activities.

References

1. Kalinnikova, Yu.G. Vliyanie fizicheskikh nagruzok i muzykal’nogo soprovozhdeniya razlichnoy ritmo­tempovoy strukturoy na bioelektricheskuyu aktivnost’ golovnogo mozga (Influence of physical exercises and music of varying rhythm and tempo on brain bioelectrical activity) / Yu.G. Kalinnikova, E.S. Inozemtseva, E.V. Galazhinskiy, D.Yu. Balanev, L.V. Kapilevich // Teoriya i praktika fizicheskoy kultury. – 2015. – № 7. – P. 5­7.
2. Kalinnikova, Yu.G. Vliyanie ritmo­tempovoy struktury na psikhofiziologicheskie kharakteristiki pri zanyatiyakh aerobikoy (Influence of rhythm­tempo structure on physiological characteristics at aerobics classes) / Yu.G. Kalinnikova, E.S Inozemtseva, L.V. Kapilevich // Teoriya i praktika fizicheskoy kultury. – 2014. – № 9. – P. 98­101.
3. Mel’nikova, T.S. Obzor ispol’zovaniya kogerentnogo analiza EEG v psikhiatrii (EEG coherence analysis in psychiatry: application review) / T.S. Mel’nikova, I.A. Lapin, V.V. Sarkisyan // Sotsial’naya i klinicheskaya psikhiatriya. – 2009. – № 1. – P. 90­94.
4. Angelopoulos E. Brain functional connectivity and the pathophysiology of schizophrenia. Psychiatriki. 2014 Apr­Jun; 25(2):91­4. English, Greek, Modern.PubMed PMID: 25035177.

Corresponding author: kapil@yandex.ru

Abstract

Objective of the study was to explore the effects of physical loads and auditory stimulation by music of varying rhythm and tempo on the intra-hemispheric EEG coherence rates.

It has been established that listening to rhythmic music strengthens the coherence of the cortical bioelectrical activity. For alpha band activity, this effect was more pronounced in the frontal lead, whereas for the theta band ­ in the occipital lead. The most remarkable effect was observed when listening to music with the RTS of maximum frequency. Physical load with different RTS suppressed coherence, while for alpha activity the effect was more pronounced at low frequencies, for theta activity ­ on the contrary, at high frequencies. Listening to music after exercise helps increase the coherence index (in some cases even higher than background levels).