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q-bio.NC · Neurons and Cognition

Off-shaft HFA power was unchanged after open-loop stimulation in 18 RAM FR2 subjects

In a pre-registered analysis of session 0 stereo-EEG data from 18 eligible subjects in the Free Recall with Open-Loop Stimulation at Encoding study (RAM FR2), we compared post-minus-pre log10 power after 4.6-second, 50 Hz open-loop trains with matched sham events at the same serial positions. At 1,243 bipolar pairs not on a stimulated shaft, the mean 70–150 Hz high-frequency activity (HFA) effect 0.5–1.5 seconds after offset was −0.03 dB (bootstrap 95% CI −0.11 to +0.05; sign-flip p = 0.517; Holm p = 0.517), showing no significant HFA change. The 3–8 Hz theta estimate was −0.21 dB (95% CI −0.43 to −0.003; p = 0.077; Holm p = 0.153), also not significant under the pre-registered Holm-corrected decision rule; a small decrease is not excluded, and the bootstrap interval may be too narrow at n = 18. The analysis included 981 stimulation trains and 498 sham events. Secondary bands were descriptive. These data do not show a lasting off-shaft HFA change in this window that could explain the reported recall decrease. Limits include one session, 18 subjects, sham events from separate no-stimulation lists, no artifact or epileptiform-event rejection, no anatomical distance measure, and uncertainty about the exact OpenNeuro release because files were read from an untagged S3 endpoint. File hashes and URLs are preserved with the results.

stereo-EEG · open-loop stimulation · free recall · high-frequency activity · theta power · memory · pre-registered analysis

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References

4
  1. usesIn 35 RAM FR2 subjects, the next word followed stimulation by a median 0.596–0.671 s and fell in 72% of post-stimulation windows sci:sha256:99f143c9aa8a2f6249f5d7c96d880fc65b1136c42b7579f6450f2df0b07aa3bb

    This run executed the pre-registered PLAN.md and code/stim_after.py of that publication without changes. Its timing audit gave the 18 eligible subjects.

  2. usesOpen-loop encoding stimulation reduced item memory across four RAM tasks, with no significant task heterogeneity or site effect sci:sha256:209b64460d28824c832357ab647a816386220a173068903d84d5d7831fbef9c5

    Its pooled finding that open-loop encoding stimulation decreases memory gives the behavioural effect that this physiological test tries to explain.

  3. usesEvent onset differs from sample-based time in 538 of 554 files across nine RAM-family iEEG datasets sci:sha256:bb1c5599a4dabaae2ebb21b53654012eb403c29b4849022010df0dd0b7490170

    Event times use the events.tsv sample column divided by fs, as that audit of RAM onset columns recommends.

  4. supportsIn 28 RAM FR2 patients, non-stimulated SEEG HFA was higher only in the first 0.25 s after stimulation offset sci:sha256:edb8bce37ebf923d2390dd48ebaeec5b087577e7a9a705eee78f990a6b6bc356

    With all trains, sham at all matched serial positions and an independent plan, off-shaft HFA 0.5-1.5 s after offset was -0.03 dB (CI -0.11 to +0.05) relative to sham. This agrees with the recovery of HFA by 0.25 s in that publication.

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