Adrien Peyrache

I’m pleased to share our new paper, “Hippocampal ripple diversity organizes neuronal reactivation dynamics in the offline brain”, out in @cp-neuron.bsky.social !

With @vitorlds.bsky.social and David Dupret, we show that diversity in ripple current profiles shapes reactivation dynamics

🚨 New paper in Nature Methods:
HippoMaps: multiscale cartography of the human hippocampus

Open-source tools & data to explore structure and function of the 🍤🧠 (histology, in/ex vivo MRI, iEEG)

Led by @jordandekraker.bsky.social

docs: hippomaps.readthedocs.io
paper: doi.org/10.1038/s415...

Just the most remarkable person and truly a beautiful soul

🕊️ The world has lost a revered conservationist -- a colossal power for what is truly good.

🕊️ Jane Goodall is a legend who helped open the door to science to the best humans among us: woman.

🕊️ She was brave, brilliant and introduced us to the best things among us: animals.

🕊️ I grieve her passing.

Come join us at University of Toronto. We're hiring a Professor of computational cognitive neuroscience.

#neuroAI #compneuro jobs.utoronto.ca/job/Toronto-...

Thanks Richard. Reminding you our little run in Chile? ;)

Post-tenure mid-life crisis project: complete ✅

3h27 at the marathon (PB!) and one very happy (if slightly zombie-like) man. Recovery phase starts now…

Fascinating work! It pinpoints the origin of dopaminergic signaling as a filter of striatal activity computing temporal difference.
Excited to dig into this manuscript.

Repeated head trauma causes neuron loss and inflammation in young athletes - Nature Repetitive head impacts from contact sports are associated with brain inflammation, vascular damage and neuron loss that are independent of hyperphosphorylated tau pathology.

So happy to see Morgane Butler, a former and brilliant undergrad student in the lab, publishing her PhD work. Looks super interesting.

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

Beautiful work showing a link between hippocampal theta sequence and learning, but not subsequent replay.

Congrats! Super interesting study.

Turns out BTSP is not All You Need™️?

« Diverse calcium dynamics underlie place field formation in hippocampal CA1 pyramidal cells. »

A fundamental study now published @elife.bsky.social

elifesciences.org/reviewed-pre...

Congrats Luke!!

Finally preprinted! TL;DR: thalamic head-direction neurons can shape their activity regardless of input. Big thanks to @apeyrache.bsky.social and master experimentalist @sskromne.bsky.social .

thanks!

Merci ;)

Hope you enjoy the read, and we’d love to hear your thoughts and comments!

Fin/13

Huge thanks to @guillaumeviejo.bsky.social and @sskromne.bsky.social for this amazing piece of work 💪

It’s been a long journey. These experiments are truly heroic: the LMN is only ~100 µm wide and sits 6 mm deep… not easy to hit with a silicon probe! 🧠🎯

12/13

In conclusion, like many other recent studies, this work shows that the thalamus is not just a relay. Here we show it can certainly generate coherent internal dynamics on its own.

11/13

Our model showed that divergent LMN inputs, local inhibition, and strong non-linear thresholds are sufficient for the ADN to form coherent pop. activity, even from random input
We predict that thalamic inhibition is crucial for this phenomenon & does certainly more than what we suggest here.
10/13

How s this possible? Unlike cortex, the thalamus lacks local excitatory loops.
We found ADN neurons switch abruptly between silent and active states, a non-linear firing mode that can create structure from noise.
This was described by @dlevenstein.bsky.social

www.biorxiv.org/content/10.1...

9/13

We silenced cortical feedback and saw LMN activity collapse into noise during non-REM, showing LMN relies on cortex to stay organized in sleep.

In the same condition, ADN neurons remained tightly coordinated even when PSB was silenced, showing the thalamus can self-organize coherent dynamics

8/13

But remember, this is the Papez circuit: the subiculum (here, PSB) projects back to the mammillary bodies (here, LMN). Is it possible that LMN activity is coordinated by cortical feedback during non-REM sleep?

7/13

During non-REM sleep, LMN activity becomes less coherent relative to wakefulness, but is not entirely random.

See here pairwise correlation during non-REM as a function of pairwise correlation during wake (ADN orange, LMN blue):

6/13

Note: during REM sleep (where brain electrical activity is virtually indistinguishable from wakefulness), everything is the same as wakefulness, suggesting that the same mechanisms are at play.
But again, during non-REM sleep, something else is happening.

5/13

The question we always had was: what about their inputs (LMN)?
So we recorded HD cell populations from both LMN and ADN, and in several animals, we managed to do it simultaneously.
While ADN cells stayed coherent during non-REM, LMN cells lost their structure, they co-fired almost randomly.

4/13

Internally organized mechanisms of the head direction sense - Nature Neuroscience Recording from population of head-direction cells across brain states, the authors provide experimental demonstration of the existence of internally organized attractor: the sequential activity of head direction neurons observed in the waking mouse persists during sleep, and this 'neuronal compass' always points toward well-defined directions.

We showed 10 years ago (already..) that thalamic HD cells remain precisely coordinated even in sleep, when external inputs vanish.
This is consistent with an internal, attractor-like mechanism.

3/13

www.nature.com/articles/nn....

HD cells tell the brain which way the head is pointing, critical for navigation.
They sit in a well-known circuit:
brainstem (lateral mammillary nuclei, LMN)
→ thalamus (anterodorsal nucleus, ADN)
→ cortex (postsubiculum, PSB)
and back to LMN! It's the Papez circuit after all.

2/13

Coherent dynamics of thalamic head-direction neurons irrespective of input While the thalamus is known to relay and modulate sensory signals to the cortex, whether it also participates in active computation and intrinsic signal generation remains unresolved. The anterodorsal...

🚨New preprint alert!

The thalamus has long been seen as a relay of sensory signals to cortex.
But could it also generate its own structured activity?
Our study explores this question in the head-direction (HD) system.

Some explanation 🧵👇 1/13

www.biorxiv.org/content/10.1...