Jan Gründemann

Pupil size modulation drives retinal activity in mice and shapes human perception - Nature Communications The pupil is known to assist retinal adaptation to light level changes. Here, the authors find a mechanism for how the pupillary light reflex drives monocular and binocular retinal activity in mice an...

The lab's first paper is out!

We find that pupil constriction in mice drives strong retinal activity in vivo, and that humans can also perceive pupil-shaped stimulus. This has repercussions for anybody using pupillometry.

🧵1/n

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

#neuroskyence #neuroscience #neuro

Serotonergic modulation of the BNST–CeA pathway reveals sex differences in fear learning - Nature Neuroscience Ravenelle et al. show that systematically increasing serotonin has sex-specific effects on fear learning in mice. In females only, increasing serotonin in the BNST enhances fear memory by promoting co...

Serotonergic modulation of the BNST–CeA pathway reveals sex differences in fear learning in mice

@friedmanlaboratory.bsky.social, @beckyravenelle.bsky.social, @elikhtik.bsky.social, @neshaburghardt.bsky.social

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

Summary figure for study of psilocybin's effect on cortical network connectivity.

New preprint + thread 🧵

#Psychedelics induce the formation of new synapses, but where do they connect?

Our rabies tracing study reveals that #psilocybin shifts connectivity across specific cortical networks.

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

1/12

Serotonin shapes the temporal window for associative fear learning https://www.biorxiv.org/content/10.1101/2025.08.06.669013v1

We were asked to write a commentary on NeuroAI for Nat. Rev. Neuro. with Sadra Sadeh, so here it is: www.nature.com/articles/s41...

We're looking for a research assistant to work in our neuroscience lab at @princetonneuro.bsky.social @hhmi.org where we study learning and decision-making circuitry.

Apply here: research-princeton.icims.com/jobs/21001/r...

Pls share w/ anyone who might be interested!

Essential role of astrocytes in rapid activity-dependent restructuration of the axon initial segment One key regulator of neuronal excitability is the axon initial segment (AIS), a highly specialized axonal region, enriched in ion channels, where action potentials are initiated. The AIS can undergo s...

'Essential role of astrocytes in rapid activity-dependent restructuration of the axon initial segment'

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

🚀 The Helmholtz AI Project Call 2025 is LIVE!
Calling all Helmholtz researchers: Apply from 1 Sept with bold, cross-center AI/ML proposals.
💡 Up to €250K INF funding available!
📍 Must involve 2+ Helmholtz centers

🔗 Learn more: www.helmholtz.ai/you-helmholt...

#AI #ProjectCall #ML

PyMouse Lifter: Real Time 3-D Pose Estimation for Mice with Only 2-D Annotation Via Data Synthesis https://www.biorxiv.org/content/10.1101/2025.08.02.668290v1

Thanks to @thetransmitter.bsky.social and @ldattaro.bsky.social for this coverage of our recent paper!

PV - Oligodendrocyte Interactions in the Infralimbic Cortex Promote Extracellular Plasticity after Safety Learning https://www.biorxiv.org/content/10.1101/2025.07.25.666881v1

The astroglial protein S100β regulates axon initial segment plasticity https://www.biorxiv.org/content/10.1101/2025.07.31.667937v1

Simultaneous 2- and 3-photon multiplane imaging across cortical layers in freely moving mice https://www.biorxiv.org/content/10.1101/2025.08.01.668113v1

Serotonin modulates neural dynamics in a subspace orthogonal to the choice space https://www.biorxiv.org/content/10.1101/2025.08.01.668048v1

Associative coding of conditioned fear in the thalamic nucleus reuniens in rodents and humans Communications Biology - The nucleus reuniens encodes associative value in both humans and rats. In rats, it also tracks defensive freezing states. The reuniens has a conserved role across species...

🚨New paper🚨 Excited to share this collaborative paper exploring nucleus reuniens correlates of fear conditioning in both rats and humans! Congrats @tugcettuna @F_Mourao_ @MicTott Muhammad Badarnee and Moh Milad!! rdcu.be/eyTPs

1/N What are the organizational principles underlying crossmodal cortical connections?
We address this in this new preprint, led by @alexegeaweiss.bsky.social & ‪@bturner-bridger.bsky.social‬ in collab w/ ‪@petrznam.bsky.social‬ @crick.ac.uk
www.biorxiv.org/content/10.1...

A thalamic circuit mechanism for stress-dependent modulation of REM sleep https://www.biorxiv.org/content/10.1101/2025.07.22.665932v1

Synaptic sign switching mediates online dopamine updates https://www.biorxiv.org/content/10.1101/2025.07.23.666367v1

Fantastic to see this collaborative work with Hopi Hoekstra out in Nature (tinyurl.com/3at3zvby). Lead by @felixbaier.bsky.social and @katjareinhard.bsky.social. Not possible without @bramnuttin.bsky.social , Chen Liu and @arnausd.bsky.social.

Excited to see where this work leads.

Corticothalamic Layer 6 Controls Cortical Activity and Thalamic Firing Mode in a Bidirectional Manner https://www.biorxiv.org/content/10.1101/2025.07.17.665299v1

Barcoded Rabies In Situ Connectomics for high-throughput reconstruction of neural circuits Sequencing of oligonucleotide barcodes holds promise as a high-throughput approach for reconstructing synaptic connectivity at scale. Rabies viruses can act as a vehicle for barcode transmission, than...

1/ Mapping synaptic connectivity between individual neurons is extremely laborious. We developed BRISC, a new method that makes it possible to map inputs onto 100s of neurons in the same animal in a matter of weeks! Led by Alex Becalick and @antblot.bsky.social. 🧵

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

Barcoded Rabies In Situ Connectomics for high-throughput reconstruction of neural circuits https://www.biorxiv.org/content/10.1101/2025.07.16.665048v1

A postnatal molecular switch drives activity-dependent maturation of parvalbumin interneurons Neuronal activity triggers PGC-1α-mediated transcriptional programs that drive the late maturation of PV+ interneurons, essential for cortical circuit function. PGC-1α partners with ERRγ and Mef2c to ...

1/10 Our latest research, led by Monika Moissidis, identifies a mechanism regulating the maturation of PV interneurons in the #cortex. This is the story @cellcellpress.bsky.social www.cell.com/cell/fulltex... ⬇︎ thread @devneuro.bsky.social @kingsioppn.bsky.social
@wellcometrust.bsky.social

(1/3) Excited to introduce our new GRAB sensors for a series of steroid hormones! These tools enable real-time detection of steroid hormone dynamics in vivo🐭🧠. Happy to share these sensors and welcome any feedback! Please contact yulonglilab2018@gmail.com for information.

The paper is out in journal format at EJN! We thank the reviewers for their insightful comments, and how they shaped the final form of this story. Check it out here: onlinelibrary.wiley.com/doi/10.1111/...

As usual, it's open access! We're getting the data ready for sharing very soon 👀🧠🧪

Amyloid pathology reduces dynamic range and disrupts neural coding in a mouse model of Alzheimer's Disease Alzheimer's Disease (AD) disrupts neural circuits vital for memory and cognition. We used two-photon microscopy to investigate these disruptions in behaving mice, focusing on the link between amyloid ...

New preprint from my lab:
Mary Ann Go et al, Amyloid pathology reduces dynamic range and disrupts neural coding in a mouse model of Alzheimer's Disease.

We used 2p imaging in mice running on an air levitated platform to study AD.

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

New plasmids available from the @massecklab.bsky.social‬! PinkyCaMP, a mScarlet-based calcium sensor, can be leveraged for its exceptional brightness, photostability, and multiplexing capabilities.
https://twp.ai/4iobS2

Mapping the projectional architecture of the mouse midbrain dopaminergic system using cell type-specific barcoding Brain-wide neural circuits are formed by the diverse axonal branching patterns of many individual neurons. Here we introduce POINTseq (projections of interest by sequencing), a high-throughput and use...

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

Event structure sculpts neural population dynamics in the lateral entorhinal cortex Our experience of the world is a continuous stream of events that must be segmented and organized at multiple timescales. The neural mechanisms underlying this process remain unknown. In this work, we...

Your brain doesn’t just passively track time ⏳ - it structures it.
In @Science.org we show that activity in 🧠 memory circuits (LEC) drifts constantly, but makes sharp jumps at key moments, segmenting life into meaningful events. (1/2)

👉 www.science.org/doi/10.1126/...

Call for 20 Assistant Professor positions Karolinska Institutet is a world-leading medical university with a long and proud history of ground-breaking research. We are now recruiting outstanding early-career researchers with particularly exce...

Karolinska is looking for 20 (!!) assistant professors and offering 6 year appointments with ~1M USD startup packages.

ki.se/en/about-ki/...