## 4 Discussion  
fNIRS network analysis was conducted to investigate the mechanism of acupuncture for gait function in patients with PD. Our previous study has confirmed that while there has been no statistically significant change in the neurotransmitter levels in the blood, acupuncture treatment improves gait disturbance in PD patients and may improve balance, cadence, including activation of the cerebral cortex [15]. In this study, we have identified the effects of acupuncture from the perspective of the brain network. The network patterns of task-evoked functional connectivity were analyzed in the whole brain region. By doing this, we tried to validate the hypothesis that acupuncture could modulate the brain network in PD patients. Hemodynamics is dynamically influenced by the formation of network structures over the entire brain. Therefore, the application of a functional connectivity study provides evidence of the mechanism of acupuncture in PD patients. Our experimental results show an increase in HbO in the M1, SMA, and PFC regions in the IG after 4 weeks of acupuncture therapy. On the other hand, in the CG (without therapy), no significant change in the activity of the ROIs was observed. In addition, the FC pattern was altered in the IG during treadmill walking, including increases in the M1 region and decreases in the PFC region after 4 weeks of acupuncture treatment. Additionally, after 4 weeks of follow-up, FC was increased in the PFC region and decreased comparatively in the M1 region in the IG. On the other hand, in the CG, FC was decreased in the M1 region after 4 weeks and tended to increase slightly after 8 weeks. Based on neuroimaging of human locomotion, two distinct locomotor control pathways have been proposed [36; 37]. The direct locomotor pathway is a neural pathway within the central nervous system (CNS) through the basal ganglia, including M1, cerebellum, and spinal cord [37; 38]. In contrast, the indirect pathway is a neuronal circuit through the basal ganglia and several associated nuclei within the CNS, including PFC, SMA, and basal ganglia [37; 38]. The indirect locomotor pathway is activated when the execution of walking is impaired, and compensatory mechanisms are necessary [13], and these assumptions support the results of our study that the PFC of PD is more activation after acupuncture therapy. The SMA region is known to be involved in gait and balance control [22; 39; 40], and previous task-related fMRI studies showed decreased activity in the SMA region of patients with PD compared to healthy controls [41]. Therefore, we suggest that this region modulates gait disruption to correct balance in patients with PD. In this study, there was no significant difference in HbO activity between the CG and IG at 0 weeks, but after 4 weeks of acupuncture treatment, there was a significant difference in HbO between the two groups in the SMA region. Furthermore, the increase in HbO in the SMA region in the IG between 0 and 4 weeks proved significant. Our findings show that acupuncture has a mitigating effect on gait dysfunction in PD patients; this effect could be linked to neural mechanisms such as cortical reorganization. Previous studies have shown that acupuncture can alter the sensory region and change the nerve conduction rate, and these effects were found to be maintained three months after therapy [42; 43]. Our results also show that the effect of acupuncture treatment was prolonged, being detected at the 4-week follow-up, which is in line with observations in the literature. In the IG, the HbO of the SMA region was increased 4 weeks after the acupuncture treatment, but there was a significant difference in the SMA and M1 regions at the 4-week follow-up after acupuncture. The peak values of HbO between the two groups, the CG and IG, also differed only in the SMA region at week 4, but there were significant differences in the SMA, M1, and PFC regions at week 8. These effects demonstrate that acupuncture treatment may have therapeutic effects lasting days to weeks.