## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Region**} & \multicolumn{2}{c}{**Pre**} & \multicolumn{2}{c}{**Post**} \\ \cline{2-5}  & **Chi-Square** & \(p\)**-Value** & **Chi-Square** & \(p\)**-Value** \\ \hline Left DLPFC \(\rightarrow\) Left M1 & 4.95 & 0.084 & 1.75 & 0.417 \\ Left DLPFC \(\rightarrow\) Right M1 & 4.53 & 0.103 & 5.99 & 0.051 \\ Left M1 \(\rightarrow\) Left DLPFC & 4.75 & 0.092 & 5.03 & 0.081 \\ Right M1 \(\rightarrow\) Left DLPFC & 8.35 & _0.015_ & 8.37 & _0.015_ \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Statistical results of relationship between the left DLPFC and M1 in patients with stroke and healthy controls. differences in EEG connectivity. Consequently, sensorimotor pathways include cortical-cortical, cortical-spinal, and cortico-cerebellar pathways [45]; moreover, depending on the location of the lesion, the disrupted pathway may vary. The difference in results in functional and effective connectivity is also a meaningful finding. In wPLI, only changes in intrahemispheric connectivity were found; however, in GC, differences in intrahemispheric connectivity and differences in interhemispheric connectivity were found. This seems to be because effective connectivity contains a causal relationship between the two channels, so it contains more information on brain connectivity [23]. In the end, new findings in brain connectivity estimators can contain more information, such as causality. The left DLPFC is a brain region associated with representative cognitive functions, which are associated with cognitive control [46]. However, it was also found that it is closely related to the motor network while being responsible for action planning [23]. During motor imagery, the activity of the left DLPFC appears because it shares a neural pathway to motor function, even if there is no real movement [47]. In this respect, the left DLPFC had no stimulation, but changes before and after stimulation were also observed in the left DLPFC due to the stimulation to the M1. In particular, the change in connectivity between the left DLPFC and ipsilesional M1 stood out. Ultimately, it is believed that the left DLPFC, which is in charge of action planning, influenced motor rehabilitation by changing the direct connection with the ipsilesional M1. Even in motor imagery without actual movement, the connectivity in the left DLPFC of patients with chronic stroke was stronger than that of healthy controls [23]. More information seems to be sent this way as the role of the left DLPFC, which is related to higher-order cognitive motor preprocessing of motor control [48], is larger. This paper has limitations. First, significant behavioral results were identified, but no significant results were observed regarding the lesion-specific group. This is expected to result from the small number of patients, and it is necessary for this to be investigated further with more data in future studies. In addition, for stable results, no sham control stroke data and a small sample size should be supplemented. Second, more detailed group settings are needed according to the location of the lesion. Even if it is an STS lesion, brain connectivity may differ depending on whether the motor cortex is included [21]. Therefore, if the number of subjects is sufficient in future studies, more sophisticated group distributions are needed, considering whether the motor cortex is included. In addition, the time of stroke is a very important variable in predicting motor impairments [49]. In this respect, it is very meaningful that the effectiveness of dual-mode stimulation in the subacute phase was demonstrated. However, further studies on the effectiveness of dual-mode stimulation in the chronic phase need to be carried out. In addition, several possible factors such as stimulation location, stimulation protocol, individual BDNF polymorphism, and lesion location can influence the effectiveness of NBS. However, this study focuses on the effect of NBS according to lesion location.