top of page
image.png
WWTNS (1).png

On Wednesday, 11 am ET

 

Organized by David Hansel, Ran Darshan

& Carl van Vreeswijk (1962-2022) 

​

​

​

About Us

About the Seminar

VVTNS  is a weekly digital seminar on Zoom targeting the theoretical neuroscience community. Created as the World Wide Neuroscience Seminar (WWTNS) in November 2020 and renamed in homage to Carl van Vreeswijk in Memoriam (April 20, 2022), its aim is to be a platform to exchange ideas among theoreticians. Speakers have the occasion to talk about theoretical aspects of their work which cannot be discussed in a setting where the majority of the audience consists of experimentalists. The seminars  are 45 min long followed by a discussion and are held on Wednesdays at 11 am ET. The talks are recorded with authorization of the speaker and are available to everybody on our YouTube channel.

 

To participate in the seminar you need to fill out a registration form after which you will

receive an email telling you how to connect.

​

​

  • Twitter
  • YouTube

Giancarlo La Camera

Stony Brook University

May 27, 2026

lacamera.jpg

Equilibrium Geometry and Chaotic Dynamics in

Large Recurrent Neural Networks

 Large recurrent networks are important models in several fields, including neuroscience, machine learning, physics, and applied mathematics. Yet their dynamics are difficult to study directly, because high-dimensional nonlinear systems can exhibit rich behavior that is hard to summarize in terms of individual trajectories. In this talk, I will discuss an approach that seeks to understand such dynamics through the structure of the network’s equilibria. I will focus on a random balanced network of threshold-linear units that undergoes a transition from a single stable equilibrium to extensive chaos as the disorder strength crosses a critical value. Using a combination of Kac–Rice theory, replica calculations, numerical root-finding, and dynamical mean-field theory, we show that the chaotic regime contains an exponentially large number of equilibria. These equilibria are all saddles, but with only a fractionally small number of unstable directions. Surprisingly, despite the completely random connectivity, the equilibria are not scattered randomly through phase space. Instead, they are strongly correlated and confined to a comparatively small region. The chaotic attractor lies within this same region, suggesting a direct geometric link between the organization of unstable equilibria and the collective structure of the dynamics. This picture helps explain why networks with extensive chaos can nevertheless display dynamics dominated by a relatively small number of collective modes. More broadly, the results suggest that the geometry of equilibria provides a useful complementary perspective to dynamical mean-field theory for understanding high-dimensional neural dynamics.  

Organizers

davidhansel.jpg
carl1.jpg

David Hansel

I am a theoretical neuroscientist at the National Center for Scientific Research in Paris, France and visiting professor at The Hebrew University in Jerusalem, Israel. I am mainly interested in the recurrent dynamics in the cortex and 

basal ganglia.

Carl van Vreeswijk *

I am a theoretical neuroscientist working at the National Center for Scientific Research in Paris, France. My main interest is the dynamics of recurrent networks of neurons in the sensory system.

*deceased

Ran Darshan

 I am a theoretical neuroscientist working at the Faculty of Medicine, the Sagol School of Neuroscience & the School of Physics and Astronomy at Tel Aviv University, Israel. I am interested in learning and dynamics of neural networks. My main goal is to achieve a mechanistic understanding of brain functions.

image.png

©2020 by WWTNS

bottom of page