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

Maria Eckstein

Google Deepmind

May 20, 2026

MariaHeadshot-1-2048x1867.jpg
  • YouTube

Towards a general model of human reward-based learning 

Traditional work in the study of human reward-based learning involves designing an experimental task---often inspired by Reinforcement Learning (RL) theory---and fits a small set of computational models---often inspired by RL algorithms---to that dataset. For example, researchers often model human behavior on bandit tasks using variants of Q-learning. While this approach has been highly productive, leading to landmark discoveries such as the dopamine reward prediction error hypothesis, it also has limitations. This talk focuses on the lack of generalizability of such models: Even if they closely fit behavior on the original task, models derived from the one-task-one-model paradigm usually predict behavior on other tasks quite poorly. I argue that this lack of generalizability is a fundamental problem for the cognitive sciences: we intuitively expect our models to be robust to superficial task differences, such as variations in the number of choice options, reward probabilities, or the exact kind of non-stationarity. I will propose potential solutions to this problem along two dimensions: the behavioral dataset and the computational model. Regarding computational models, I will introduce work in which we moved beyond the limitations of hand-crafted one-off models by employing flexible, data-driven methods. These methods allowed us to compare classes of models instead of individual model instances, allowing us to cover the space of possible models more exhaustively, and innovate cognitive mechanisms very efficiently. For the behavioral dataset, we move from using single learning tasks to a comprehensive task space that encompasses most existing paradigms in the literature, while closing the gaps between them in a near-continuous fashion. Our results suggest that more general models in conjunction with broader datasets can pave the road toward increasingly general models of human reward-based learning and decision making, and a persistent departure from many aspects of RL theory.

Released July 30, 2026

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.  

  • YouTube

Released August 4, 2026

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