Alex van Meegen
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avm.bsky.social
Alex van Meegen
@avm.bsky.social
Theory of Neural Networks (how the heck do they work?) | Postdoc @EPFL, prev. Swartz Fellow @Harvard and PhD @FZJuelich | https://alexvanmeegen.github.io | Background art by https://bettina-hachmann.de
Reposted by Alex van Meegen
Connectome datasets alone are generally not sufficient to predict neural activity. However, pairing connectivity information with neural recordings can produce accurate predictions of activity in unrecorded neurons

www.nature.com/articles/s41...
Prediction of neural activity in connectome-constrained recurrent networks - Nature Neuroscience
The authors show that connectome datasets alone are generally not sufficient to predict neural activity. However, pairing connectivity information with neural recordings can produce accurate predictio...
www.nature.com
November 10, 2025 at 10:12 PM
This was a lot of fun! From my side, it started with a technical Q: what's the relation between two-side cavity and path integrals? Turns out it's a fluctuation correction - and amazingly, this also enable the "O(N) rank" theory by @david-g-clark.bsky.social and @omarschall.bsky.social. 🤯
Now in PRX: Theory linking connectivity structure to collective activity in nonlinear RNNs!
For neuro fans: conn. structure can be invisible in single neurons but shape pop. activity
For low-rank RNN fans: a theory of rank=O(N)
For physics fans: fluctuations around DMFT saddle⇒dimension of activity
Connectivity Structure and Dynamics of Nonlinear Recurrent Neural Networks
The structure of brain connectivity predicts collective neural activity, with a small number of connectivity features determining activity dimensionality, linking circuit architecture to network-level...
journals.aps.org
November 5, 2025 at 9:15 AM
Reposted by Alex van Meegen
First paper from the lab!
We propose a model that separates estimation of odor concentration and presence and map it on olfactory bulb circuits
Led by @chenjiang01.bsky.social and @mattyizhenghe.bsky.social joint work with @jzv.bsky.social and with @neurovenki.bsky.social @cpehlevan.bsky.social
November 4, 2025 at 3:40 PM
Reposted by Alex van Meegen
Applying to do a postdoc or PhD in theoretical ML or neuroscience this year? Consider joining my group (starting next Fall) at UT Austin!
POD Postdoc: oden.utexas.edu/programs-and... CSEM PhD: oden.utexas.edu/academics/pr...
October 23, 2025 at 9:36 PM
Reposted by Alex van Meegen
A study led by Cina Aghamohammadi is now out in ‪@natcomms.nature.com‬! We developed a mathematical framework for partitioning spiking variability, which revealed that spiking irregularity is nearly invariant for each neuron and decreases along the cortical hierarchy.
www.nature.com/articles/s41...
October 12, 2025 at 12:42 AM
Reposted by Alex van Meegen
🎉 "High-dimensional neuronal activity from low-dimensional latent dynamics: a solvable model" will be presented as an oral at #NeurIPS2025 🎉

Feeling very grateful that reviewers and chairs appreciated concise mathematical explanations, in this age of big models.

www.biorxiv.org/content/10.1...
1/2
September 19, 2025 at 8:01 AM
Reposted by Alex van Meegen
Lab members are at the Bernstein conference @bernsteinneuro.bsky.social with 9 posters! Here’s the list:

TUESDAY 16:30 – 18:00

P1 62 “Measuring and controlling solution degeneracy across task-trained recurrent neural networks” by @flavioh.bsky.social
September 30, 2025 at 9:29 AM
Reposted by Alex van Meegen
Check out our new preprint where we analyzed the dynamics of over ten thousand neurons across 223 brain areas and found a surprising universal principle that describes the organization of intrinsic timescales across the entire mouse brain, including subcortical structures!
#neuroskyence
Excited to share our new preprint on the brain-wide organization of intrinsic timescales at single neuron resolution. Work w/ @roxana-zeraati.bsky.social, @intlbrainlab.bsky.social, Anna Levina, @engeltatiana.bsky.social : www.biorxiv.org/content/10.1...
September 3, 2025 at 6:52 AM
Reposted by Alex van Meegen
Since I'm back on BlueSky - with @frostedblakess.bsky.social and @cpehlevan.bsky.social we wrote a brief perspective on how ideas about summary statistics from the statistical physics of learning could potentially help inform neural data analysis... (1/2)
Frontiers | Summary statistics of learning link changing neural representations to behavior
How can we make sense of large-scale recordings of neural activity across learning? Theories of neural network learning with their origins in statistical phy...
www.frontiersin.org
September 4, 2025 at 6:30 PM
Reposted by Alex van Meegen
Excited to share new computational work, led by @jzv.bsky.social, driven by Juan Carlos Fernandez del Castillo + contribution from Farhad Pashakanloo. We recover 3 core motifs in the olfactory system of evolutionarily distant animals using a biophysically-grounded model + efficient coding ideas!
Convergent motifs of early olfactory processing are recapitulated by layer-wise efficient coding
The architecture of early olfactory processing is a striking example of convergent evolution. Typically, a panel of broadly tuned receptors is selectively expressed in sensory neurons (each neuron exp...
www.biorxiv.org
September 4, 2025 at 4:51 PM
Reposted by Alex van Meegen
(1/26) Excited to share a new preprint led by grad student Albert Wakhloo, with me and Larry Abbott: "Associative synaptic plasticity creates dynamic persistent activity."
www.biorxiv.org/content/10.1...
Associative synaptic plasticity creates dynamic persistent activity
In biological neural circuits, the dynamics of neurons and synapses are tightly coupled. We study the consequences of this coupling and show that it enables a novel form of working memory. In recurren...
www.biorxiv.org
August 25, 2025 at 5:17 PM
Reposted by Alex van Meegen
I wrote a Comment on neurotheory, and now you can read it!

Some thoughts on where neurotheory has and has not taken root within the neuroscience community, how it has shaped those subfields, and where we theorists might look next for fresh adventures.

www.nature.com/articles/s41...
Theoretical neuroscience has room to grow
Nature Reviews Neuroscience - The goal of theoretical neuroscience is to uncover principles of neural computation through careful design and interpretation of mathematical models. Here, I examine...
www.nature.com
August 20, 2025 at 4:09 PM
Reposted by Alex van Meegen
Wanted to share a new version (much cleaner!) of a preprint on how connectivity structure shapes collective dynamics in nonlinear RNNs. Neural circuits have highly non-iid connectivity (e.g., rapidly decaying singular values, structured singular-vector overlaps), unlike classical random RNN models.
Connectivity structure and dynamics of nonlinear recurrent neural networks
Studies of the dynamics of nonlinear recurrent neural networks often assume independent and identically distributed couplings, but large-scale connectomics data indicate that biological neural circuit...
arxiv.org
August 19, 2025 at 3:42 PM
Reposted by Alex van Meegen
Excited to announce that my first postdoc paper is now online!

Links:
www.nature.com/articles/s41...
rdcu.be/eAcN7

In it, we examine the perennial question: what changes in the brain when learning a new motor skill?

Read more below to find out 👇
Differential kinematic coding in sensorimotor striatum across behavioral domains reflects different contributions to movement - Nature Neuroscience
Hardcastle and Marshall et al. show that striatal function is domain specific, required for task-related but not spontaneously expressed movements. This functional distinction is reflected in starkly ...
www.nature.com
August 12, 2025 at 6:26 PM
Reposted by Alex van Meegen
Coming March 17, 2026!
Just got my advance copy of Emergence — a memoir about growing up in group homes and somehow ending up in neuroscience and AI. It’s personal, it’s scientific, and it’s been a wild thing to write. Grateful and excited to share it soon.
August 4, 2025 at 4:21 PM
Reposted by Alex van Meegen
Physik studieren? Oder ein anderes Fach?

In Göttingen geht jetzt beides, mit dem "Bachelor Interdisziplinär", der Physik mit spannenden Disziplinen Eurer Wahl, wie z.B. Künstlicher Intelligenz, Philosophie, Neurowissenschaften, ... kombiniert.

www.uni-goettingen.de/de/studium/6...
Studiengang Physik interdisziplinär - Georg-August-Universität Göttingen
Webseiten der Georg-August-Universität Göttingen
www.uni-goettingen.de
July 19, 2025 at 5:30 AM
Reposted by Alex van Meegen
Out today in @nature.com: we show that individual neurons have diverse tuning to a decision variable computed by the entire population, revealing a unifying geometric principle for the encoding of sensory and dynamic cognitive variables.
www.nature.com/articles/s41...
June 25, 2025 at 10:38 PM
Reposted by Alex van Meegen
(1/23) In addition to the new Lady Gaga album "Mayhem," my paper with Manuel Beiran, "Structure of activity in multiregion recurrent neural networks," has been published today.

PNAS link: www.pnas.org/doi/10.1073/...

(see dclark.io for PDF)

An explainer thread...
Structure of activity in multiregion recurrent neural networks | PNAS
Neural circuits comprise multiple interconnected regions, each with complex dynamics. The interplay between local and global activity is thought to...
www.pnas.org
March 7, 2025 at 7:39 PM
Interested in high-dim chaotic networks? Ever wondered about the structure of their state space? @jakobstubenrauch.bsky.social has answers - from a separation of fixed points and dynamics onto distinct shells to a shared lower-dim manifold and linear prediction of dynamics.
(1/3) How to analyse a dynamical system? Find its fixed points, study their properties!

How to analyse a *high-dimensional* dynamical system? Find its fixed points, study their properties!

We do that for a chaotic neural network! finally published: doi.org/10.1103/Phys...
Fixed point geometry in chaotic neural networks
Understanding the high-dimensional chaotic dynamics occurring in complex biological systems such as recurrent neural networks or ecosystems remains a conceptual challenge. For low-dimensional dynamics...
doi.org
June 10, 2025 at 7:45 PM
Reposted by Alex van Meegen
Our new preprint 👀
June 9, 2025 at 7:32 PM
Reposted by Alex van Meegen
Our work on how continuous attractors emerge in unstructured RNNs is now out in PRX Life #PRXLife :
journals.aps.org/prxlife/abst...

Work done with @tankutcan.bsky.social

@sesamedusa.bsky.social
Emergence of Robust Memory Manifolds
Frozen stabilization enables small unstructured neural networks to form robust continuous memories and exhibit separation of timescales without fine-tuning or symmetries.
journals.aps.org
May 6, 2025 at 10:40 PM
Reposted by Alex van Meegen
I'll be presenting this at #cosyne2025 (poster 3-50)!

I'll also be giving a talk at the "Collectively Emerged Timescales" workshop on this work, plus other projects on emergent dynamics in neural circuits.

Looking forward to seeing everyone in 🇨🇦!
March 26, 2025 at 6:54 PM
Reposted by Alex van Meegen
Excited to present the latest from the lab out today in Cell www.cell.com/cell/fulltex.... See Thread! 1/8
March 4, 2025 at 4:34 PM
Reposted by Alex van Meegen
We always see that 1) neural responses are very diverse 2) the shattering dimensionality is as high as it can be. Now also in an extensive analysis of the IBL dataset. Wonderful collaboration with @lorenzoposani.com, Shuqi Wang, Samuel Muscinelli, Liam Paninski. Many new analyses in this new version
February 13, 2025 at 2:52 PM
Reposted by Alex van Meegen
(1/5) Excited to share my work with @engeltatiana.bsky.social , out now in Nat Neuro! We show that RNNs use low-d latent circuit mechanisms for cognitive tasks. We find that context-dependent decisions in both RNNs and PFC arise from latent inhibitory mechanisms. www.nature.com/articles/s41...
Latent circuit inference from heterogeneous neural responses during cognitive tasks - Nature Neuroscience
The latent circuit model identifies low-dimensional mechanisms of task execution from heterogenous neural responses. This approach reveals a latent inhibitory mechanism for context-dependent decisions...
www.nature.com
February 12, 2025 at 6:16 PM