🧠 New preprint!. We used human intracranial EEG + pharmacology to test a core question in memory research: is hippocampal theta required for retrieval?. Turns out it’s not—and may instead reflect a reinstated encoding mode. 👇 Thread.

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Bottom line:. 📉 Theta ≠ Retrieval. 📈 Theta = Encoding/Updating. This subtle but important shift reframes how we think about the neural basis of memory, and why cholinergic drugs help some processes and not others. 🧵 Full details ⬇

In analyses led by @ZabehErfan, we also show that neural dynamics under cholinergic blockade can be decoded from low-dimensional features of LFPs across electrodes.

This has big implications:.🧬 Memory models: Theta may unify encoding & re-encoding, not retrieval.🧠 Neurophysiology: Reinstatement may reflect reactivation of an encoding mode, not just stored content.🧪 Alzheimer’s: Targets for modulating cholinergic tone may need rethinking.

Our data show:.– Theta power & phase reset are disrupted by cholinergic blockade at retrieval.– But memory remains intact.– Reinstatement of spectral patterns from encoding is also impaired. → Retrieval still works without theta, but maybe in a different form.

This challenges long-held theories that hippocampal theta reflects retrieval-specific computations. Instead, we propose a unifying framework: theta during retrieval reflects re-engagement of encoding-related neural states, perhaps to update or integrate memory—not retrieve it.

When scopolamine was present at encoding, patients had selective recollection deficits and disrupted hippocampal theta. But when the drug was present only at retrieval, memory was spared—even though theta power, phase reset, and reinstatement were disrupted.

We gave scopolamine (a muscarinic cholinergic blocker) to epilepsy patients with implanted hippocampal electrodes as they performed a memory task. By injecting the drug before retrieval vs. before encoding we could tease apart the role of theta oscillations at each memory stage.

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RT @UeliRutishauser: Delighted to announce our latest work in @NatureHumBehav. While watching movies, theta phase precession is triggered b….

RT @Tomdonoghue: 📜🎉 I have a new preprint: a systematic review of clinical investigations of aperiodic activity!. I reviewed 143 reports fr….

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