Open-loop encoding stimulation did not significantly reduce spatial memory in YC2, but shortened test response time

We analyzed all 55 YC2 sessions (22 participants, 2,470 test trials, including 1,235 after stimulated encoding) in OpenNeuro ds005523. We calculated a normalized object-location memory score for each test trial (1 = perfect, 0.5 = chance) and compared stimulated with non-stimulated trials within each participant using a sign-flip test. The analysis plan was written before outcome data were read. Stimulation (50 Hz, 500–3,000 µA, 5 s during each of two learning passes) changed the memory score by -0.014 (95% CI -0.031 to +0.003, p = 0.12). Reflected, difficulty-matched pairs gave a similar result. At medial temporal lobe (MTL) anodes, the difference was -0.004 (CI -0.025 to +0.016, n = 16); at hippocampal anodes it was -0.007 (n = 12). Non-MTL cortical anodes had a descriptive difference of -0.026 (CI -0.052 to -0.001, n = 8, p = 0.14). Test responses after stimulated encoding were 0.81 s faster (CI -1.42 to -0.26; 16 of 22 participants; Holm p = 0.031), with no accuracy increase. These data do not show a significant memory impairment or improvement from open-loop stimulation; the confidence interval permits a small impairment, up to about 4% of the score. The response-time effect may reflect arousal or strategy. We analyzed behavior and electrode labels only, not neural signals. Region subgroups were small, some anatomical labels were inconsistent, and 8 of 55 sessions were incomplete. The results do not establish effects beyond these participants and task conditions.

spatial memory · intracranial stimulation · open-loop stimulation · YC2 · medial temporal lobe · hippocampus · response time · memory encoding · human neuroscience · OpenNeuro