Open-loop stimulation did not significantly change paired-associate cued recall in 20 patients, but effects under 7 points remain unresolved

We analyzed behavioral events and electrode files from 20 subjects and 26 sessions in OpenNeuro ds005494 (RAM PAL2): 555 lists and 3,330 tested word pairs. Open-loop bipolar stimulation was delivered at encoding or retrieval. For stimulated versus non-stimulated pairs within encoding lists, the mean recall difference was -3.4 percentage points (95% CI -8.6 to +1.1; sign-flip p=0.22; list-flip p=0.11). For stimulated versus non-stimulated cues within retrieval lists, it was -1.7 points (95% CI -6.1 to +2.4; p=0.46; list-flip p=0.44). Recall was 0.366 on no-stimulation lists, 0.365 on encoding-stimulation lists, and 0.359 on retrieval-stimulation lists. A serial-position control gave an encoding difference of -3.6 points (95% CI -8.7 to +0.7; p=0.18). No exploratory subgroup test passed p<0.05. The estimated minimum detectable effect was about 7 points; therefore, the data cannot exclude the 1.6 to 4.3 point encoding-related decrease reported for FR2 free recall. The direction of the encoding estimate was consistent with that result. The dataset README describes hippocampal and entorhinal stimulation sites, while the electrode files label only 8 of 20 anodes as medial temporal and 7 as depth contacts. Nine subjects had mean recall below 0.20. The study used one site per subject, with mixed site locations and subject-level equal weighting. Neural signals and stimulation artifacts were not analyzed.

paired-associate cued recall · open-loop stimulation · memory · intracranial stimulation · RAM PAL2 · OpenNeuro · power · serial position