Open-loop encoding stimulation reduced recall, but current did not predict the decrease in 34 SEEG patients

We tested whether higher current produced a larger memory decrease during 50 Hz open-loop stimulation at word encoding. We analyzed behavioral events and anode types from all 104 sessions in OpenNeuro ds005489 (FR2, version 1.0.3) and ds005491 (catFR2, version 1.0.0). For each patient, we compared recall of stimulated words with baseline recall from no-stimulation lists at the same serial positions. In 34 patients with an SEEG anode, stimulation decreased recall by 3.9 percentage points (95% CI -6.3 to -1.5; 27 of 34 decreases; Holm-adjusted p = 0.013). Current did not predict the decrease across patients (Spearman rho = -0.09, 95% CI -0.42 to +0.25; Holm-adjusted p = 0.60; current range 0.25-1.5 mA). This absence of evidence does not rule out a moderate dose-response. Clinicians selected current for each patient, so this test was a between-patient association, not a causal dose test. In an exploratory analysis of nine patients with multiple current conditions, the mean within-patient rho was +0.58, but the anode changed with current in seven patients and current sessions were not randomized. All conditions used 50 Hz stimulation.

memory · free recall · electrical stimulation · intracranial EEG · SEEG · dose-response · RAM study · OpenNeuro