Connectionists: World wide VVTNS series (6th season): Wednesday, 26, 2025, at 11:00 am ET - Alfonso Renart | Champalimaud Centre for the Unknown, Lisbon

[David Hansel]

[image: VVTNS.png]
https://www.wwtns.online
<https://streaklinks.com/A9c7PbbpKY7PxB6PaAJWGD3-/https%3A%2F%2Fwww.wwtns.online>
-
on twitter: wwtns at TheoreticalWide

You are cordially invited to  the lecture

Alfonso Renart

Champalimaud Centre for the Unknown, Lisbon

 on the topic of

Flexible analog computation in low-rank balanced spiking networks

The lecture will be held on zoom on November 26, 2025, at *11:00 am ET *

> To receive the link: https://www.wwtns.online/register-page
>

*Abstract: *Recurrent networks with balanced excitation-inhibition explain
a wide range of neurophysiological observations, but can only implement a
limited set of transformations on their input. On the other hand networks
of firing-rate units with low-rank connectivity have universal
computational capabilities, but do not work with spikes or generate noise
self-consistently. Although empirical approaches to merge these two
computational frameworks have been constructed, there is no established
theory describing their unification. Here we develop such a theory. We
study analytically and numerically networks with connectivity comprising
random “strong”, and low-rank “weak” components. When the low-rank
connectivity is slow, a well-defined notion of instantaneous firing rate
emerges which implies universal computation as previously shown. However,
the fact that such time-varying rates are the result of E-I balance has
important implications. We show that internally or externally generated
fluctuations along particular latent modes tend to break the E-I balance.
Its maintenance is obtained through the emergence of a spontaneous coupling
between the mean and the variance of the membrane potential and the norm of
the latent state driving these modes. This leads to several predictions,
the most counterintuitive of which is that coherent global fluctuations in
subthreshold membrane potential (Vm) should coexist with desynchronized
activity at constant firing rates when the dynamics of these modes is
excited. To test our theory, we show that the coupling between the average
Vm and the latent state adds new non-linear dimensions to the
low-dimensional manifold of the network, which lead to a frequency doubling
when the input to the network is periodic, a prediction that is borne out
in population recordings from mouse V1. Our results unify two prevalent
frameworks for cortical computation and clarify the relationship between
computation, dynamics and geometry in circuits of spiking neurons.


*About VVTNS : Launched as the World Wide  Theoretical Neuroscience Seminar
(WWTNS) in November 2020 and renamed in homage to Carl van Vreeswijk in
Memoriam (April 20, 2022), 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, **held on Wednesdays at 11 am ET,**  are 45-50 min long followed
by a discussion. The talks are recorded with authorization of the speaker
and are available to everybody on our YouTube channel.*


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-- 
*Il n'y a ni obligation ni pression à traiter ou répondre à ce mail en
dehors des heures de travail*

"В каждой шутке есть доля шутки"

'Life is good ..' (Carl van Vreeswijk, 1962-2022)
---------------------------------------
David Hansel
Directeur de Recherche  au CNRS
Co-Group leader
Cerebral Dynamics Plasticity and Learning lab., CNRS
45 rue des Saints Peres 75270 Paris Cedex 06
Tel (Cell):   +33 607508403 - Fax (33).1.49.27.90.62

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