Location and strength reliability of superficial target toward transcranial magnetic stimulation guided with...

Individualized transcranial magnetic stimulation (TMS) can be optimized using functional connectivity (FC). Compared to undirected FC, effective connectivity (eFC) reveals causal relationships between brain regions but lacks reliability evaluation for guiding TMS targets.

This study investigated the test-retest reliability of eFC-guided superficial targets (i.e., location and strength) using functional MRI data from 29 healthy participants. We simulated clinical scenarios targeting four deep regions (i.e., the subgenual anterior cingulate cortex [sgACC], posterior cingulate cortex [PCC], and bilateral nucleus accumbens [NAc]) via two superficial regions (i.e., dorsal lateral prefrontal cortex [DLPFC] and inferior parietal lobe [IPL]). Subsequently, both the peak location and center of gravity (COG) were applied to obtain the personalized superficial target compared using intra-individual distance and intraclass correlation coefficients (ICC).

Our findings showed significant negative eFC from DLPFC to NAc/sgACC and positive eFC from IPL to PCC. ICC values for eFC strength ranged from 0.07 to 0.13. Regarding spatial stability, the COG method exhibited smaller intra-individual distances (1-22 mm) compared to the peak location method (0-57 mm). However, the peak location method yielded significantly stronger eFC than the COG method (mean = -0.15 vs 0.004).

Despite lower spatial stability, the peak-based method maximizes causal strength for eFC-guided TMS, but its potential neuromodulatory or clinical relevance remains to be validated in future translational studies.