Excited to share our new paper on theta-phase locking of single neurons during human spatial memory:

www.nature.com/articles/s41...

With @lukaskunz.bsky.social, Joshua Jacobs, and our colleagues from the University of Freiburg

Despite recent criticism from Quiroga to our claim that Concept Neurons emerge from Conjunctive Coding Neurons we claim: “And yet, the hippocampus codes conjunctively!”.
We hope it sparks a smile (and maybe a few debates).

Read here: tinyurl.com/3ycv3vj2

🧠 Paper out!

We investigated how hippocampal and cortical ripples support memory during movie watching. We found that:

🎬 Hippocampal ripples mark event boundaries
🧩 Cortical ripples predict later recall

Ripples may help transform real-life experiences into lasting memories!

rdcu.be/eui9l

Cholinergic blockade reveals role for human hippocampal theta in encoding but not retrieval https://www.biorxiv.org/content/10.1101/2025.05.12.653487v1

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 ⬇
www.biorxiv.org/content/10.1...

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:
🧬 For memory models: Theta may unify encoding & re-encoding, not retrieval per se
🧠 For neurophysiology: Reinstatement might reflect reactivation of an encoding mode, not just stored content
🧪 For 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.

Hi Bluesky! First post here. Kicking things off with a new preprint.

🧠 Using human iEEG + pharmacology, we asked: is hippocampal theta required for retrieval?

Turns out it’s not. Instead, it may reflect a reinstated encoding mode.

Thread below.
www.biorxiv.org/content/10.1...