Functional Connectivity Increases in Response to High-Definition Transcranial Direct Current Stimulation in Patients with Chronic Disorder of Consciousness

Abstract

High-definition transcranial direct current stimulation (HD-tDCS) has been shown to play an important role in improving consciousness in patients with disorders of consciousness (DOCs), but its neuroelectrophysiological evidence is still lacking. To better explain the electrophysiological mechanisms of the effects of HD-tDCS on patients with DOCs, 22 DOC patients underwent 10 anodal HD-tDCS sessions of the left dorsolateral prefrontal cortex (DLPFC). This study used the Coma Recovery Scale-Revised (CRS-R) to assess the level of consciousness in DOC patients. According to whether the CRS-R score increased before and after stimulation, DOC patients were divided into a responsive group and a non-responsive group. By comparing the differences in resting-state EEG functional connectivity between different frequency bands and brain regions, as well as the relationship between functional connectivity values and clinical scores, the electrophysiological mechanism of the clinical effects of HD-tDCS was further explored. The change of the phase locking value (PLV) on the theta frequency band in the left frontal–parietooccipital region was positively correlated with the change in the CRS-R scores. As the number of interventions increased, we observed that in the responsive group, the change in PLV showed an upward trend, and the increase in the PLV appeared in the left frontal–parietooccipital region at 4–8 Hz and in the intra-bifrontal region at 8–13 Hz. In the non-responsive group, although the CRS-R scores did not change after stimulation, the PLV showed a downward trend, and the decrease in the PLV appeared in the intra-bifrontal region at 8–13 Hz. In addition, at the three-month follow-up, patients with increased PLV in the intra-bifrontal region at 8–13 Hz after repeated HD-tDCS stimulation had better outcomes than those without. Repeated anodal stimulation of the left DLPFC with HD-tDCS resulted in improved consciousness in some patients with DOCs. The increase in functional connectivity in the brain regions may be associated with the improvement of related awareness after HD-tDCS and may be a predictor of better long-term outcomes.

Combined behavioral and EEG evidence for the 70 Hz frequency selection of short‐term spinal cord stimulation in disorders of consciousness

“…Hermann found that the theta–alpha PO connectivity was a reliable marker of improved consciousness in tDCS responders targeting the DLPFC 46 . A similar study also found that the changes in left frontal‐parieto‐occipital theta connectivity were positively correlated with the changes in CRS‐R scores after high‐definition tDCS (HD‐tDCS) intervention 47 . In contrast, a study used HD‐tDCS targeting the precuneus as a treatment for patients with DOC and revealed that improved consciousness was accompanied by an increase in mean PO connectivity in the beta band and the whole brain in the gamma band 48 .…”

Combining HD-tDCS with music stimulation for patients with prolonged disorders of consciousness: Study protocol for an RCT trial

“…Sample size estimation was conducted using G*Power software. The effect size value was calculated based on previous similar studies ( Han et al, 2022b ), with f = 0.47, α= 0.05, and power (1-β) = 0.95. Considering a potential participant attrition rate of 20%, the total sample size was determined to be 90 cases.…”

Frontal tDCS reduces alcohol relapse rates by increasing connections from left dorsolateral prefrontal cortex to addiction networks

“…There is growing evidence from non-invasive intervention studies that DLPFC stimulation can modulate RSFC [27][28][29][30][31]. An early study on healthy controls, reported that one tDCS session stimulating bilateral DLPFC modulated RSFC of the default mode, fronto-parietal, and interceptive networks [32].…”