Precise Timing Matters: Modulating Human Memory by Synchronizing Hippocampal Stimulation to Saccadic Event Related Potentials
Bibliographic record
Abstract
Abstract Episodic memory, the ability to record and relive experiences, is intricately connected to visual exploration in most humans. This study explores the possibility that eye movements create physiological states relevant for memory, analogous to those associated with hippocampal theta. Previous work has demonstrated that saccadic eye movements, which occur roughly at theta frequency, elicit hippocampal event-related potentials (ERPs). Building on the Separate Phases of Encoding and Retrieval (SPEAR) model, we asked if the peaks and troughs of this saccadic ERP are differentially important for memory formation. Specifically, we applied saccade-contingent hippocampal electrical stimulation at estimated ERP peaks and troughs while individuals with epilepsy visually explored natural scenes across 59 sessions. We subsequently assessed their recognition memory for scenes and their recall of associated targets. Results indicate that memory is robust when stimulation precisely targets the peak or trough, contrasting with impairments observed with random stimulation. Moreover, memory impairment is prominent when stimulation is applied within 100 ms of saccade initiation, a time that reflects high medial temporal lobe inhibition. Our findings suggest that the hippocampus rapidly evolves through memory-relevant states following each eye movement, while also challenging the assumption that human saccadic ERP peaks and troughs mirror the encoding and retrieval phases of theta rhythms studied in rodents. The study sheds light on the dynamic interplay between eye movements, hippocampal activity, and memory formation, offering theoretical insights with potential applications for memory modulation in neurological disorders. Significance Statement Why do eye-movements enhance memory formation? Here, we causally tested if eye-movements initiate short-lived states critical for memory formation within the hippocampus, a brain region known to support memory. We built a system that could precisely apply hippocampal electrical stimulation at key moments after eye-movements to test how the timing of this stimulation influenced people’s ability to form memories. We found that stimulation was particularly disruptive to memory formation when applied within 100 ms of initiating an eye movement. By contrast, memory was robust to stimulation precisely timed to the peak and trough of hippocampal eye-movement responses. We interpret this temporal evolution of memory-relevant states within a prominent model of how theta phases relate to rodent memory.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".