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. 2022 Mar 10;12(3):432.
doi: 10.3390/jpm12030432.

Whole Brain Hemodynamic Response Based on Synchrony Analysis of Brain Signals for Effective Application of HD-tDCS in Stroke Patients: An fNIRS Study

Gihyoun Lee  1   2 , Jungsoo Lee  3 , Jinuk Kim  1   2 , Heegoo Kim  1   2 , Won Hyuk Chang  2 , Yun-Hee Kim  1   2   4
Affiliations

Whole Brain Hemodynamic Response Based on Synchrony Analysis of Brain Signals for Effective Application of HD-tDCS in Stroke Patients: An fNIRS Study

Gihyoun Lee et al. J Pers Med. .

Abstract

In this study, the effective application of high-definition transcranial direct current stimulation (HD-tDCS) based on the whole brain hemodynamic response in stroke patients was investigated using functional near-infrared spectroscopy (fNIRS). The intrahemispheric and interhemispheric synchronization and cortical activity based on the time during 1 mA HD-tDCS were examined in 26 chronic cerebrovascular disease patients. At the beginning of HD-tDCS, the synchronization and brain activity in the whole brain increased rapidly and decreased after 5 min. In the middle of tDCS, the synchronization began to increase again, and strong synchronic connections were formed around the desired stimulation area. After tDCS, strong cortical activation was observed in the stimulation area, indicating that the baseline of the oxyhemoglobin (HbO) signal increased in the desired stimulation area. Therefore, the results of this study indicate that HD-tDCS can be applied efficiently to enhance the effect of tDCS. This stimulation method with tDCS can be explored clinically for more neurorehabilitation of patients with degenerative brain diseases.

Keywords: HD-tDCS; brain signal synchronization; fNIRS; hemodynamic response; stroke patients.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Experimental design. (A) Experimental conditions. (B) A head cap including the tDCS electrodes and fNIRS optodes. (C) Topography for tDCS electrodes and fNIRS optodes location.
Figure 2
Figure 2
The average cortical activation maps of 26 subjects analyzed by using the NIRS-SPM software before (prerest), during, and after (post-rest) tDCS intervention.
Figure 3
Figure 3
The cortical synchrony results analyzed by using the OptoNet II® software based on the total 22 timeframes in all 26 subjects. The green circles—functional brain regions, the colored lines—the synchrony connections, the lightning mark—the tDCS target.
Figure 4
Figure 4
The mean PLV values based on the timeframe in each hemisphere and a whole brain. The error bar indicates the standard deviations between all related channels. The asterisk indicates a statistical difference compared to the pre-test value (* p < 5/100; ** p < 1/100; *** p < 1/1000), and the cross indicates a statistical difference between affected and unaffected intrahemispheric connections († p < 5/100; †† p < 1/100; ††† p < 1/1000).
Figure 5
Figure 5
The number of synchrony connections over the threshold level before (pre-test), during, and after (post-rest) tDCS intervention. (A) Inter synchrony showed number of synchrony connections between the two hemispheres. Intra synchrony showed number of synchrony connections within the unaffected hemisphere (B) and the affected hemisphere (C). The asterisk indicates a statistical difference compared to the pre-test value (* p < /1005; ** p < 1/100)).
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