Lateral position predicts clinician-chosen stimulation current, but within-shaft evidence is not significant

An independent replication and extension of an earlier SCI result tested whether lateral position or depth along a stereo-EEG (SEEG) shaft was associated with current used to evoke visual percepts. The analysis used 112 stimulations in 20 patients from OpenNeuro ds005169 v1.0.0; all included stimulations caused a visual percept. Outcome was log2 current (mA), demeaned within patient. Lateral distance |x| correlated with current (Spearman rho +0.34; one-sided within-patient permutation p=0.0003), matching the earlier result; 11 of 14 patients with at least 3 stimulations and a current change had a positive association (median rho +0.31; one-sided Wilcoxon p=0.018). Contact number, a proxy for depth (contact 1 is deepest), and |x| were strongly associated (rho +0.68). After controlling for contact number, the |x| association remained (partial rho +0.27, p=0.007); after controlling for |x|, the contact-number association was near zero (partial rho -0.01, p=0.55). Within the same shaft, the association was smaller and not significant (32 shafts, 83 stimulations; rho +0.20, p=0.063). Between-shaft means showed an association (61 shaft means; rho +0.39, two-sided scipy p=0.002). These findings are consistent with |x|, or a linked variable, rather than shaft depth, but do not show that moving along one shaft changes current; shaft-level factors such as target region may explain the effect. The currents were clinician-chosen currents for stimulations that caused percepts, not measured thresholds, and non-percept stimulations are absent. Coordinates are in each patient's native scanner frame, are not comparable between patients, and head rotation can mix x and y. Seven of 112 pairs had a contact absent from electrodes.tsv; its coordinates were fitted along the shaft. The sample was small (20 patients, 112 stimulations, 24 shafts with a current change), and the within-shaft test had low power.

stereo-EEG · intracranial stimulation · visual percepts · current · lateral position · contact number · OpenNeuro · replication