Journal club dei sistemi Complessi

Questo ciclo di seminari si propone di presentare agli studenti della Magistrale in Fisica alcuni temi rilevanti nell'ambito dei sistemi complessi. A questi incontri sono dedicate due ore, vi sara' quindi ampio spazio per contestualizzare gli argomenti, per fare domande e discutere con l'oratore. Per ulteriori informazioni o proposte di seminario contattare: Giuseppe Luca Celardo, giuseppeluca.celardo@unifi.it

Title :  A robust balancing mechanism for spiking neural networks

Abstract :

Neurons in the brain cortex fire irregularly and with a low firing
rate despite being subject to a
continuous stimulation (bombardment) from thousands of connected
neurons. This seemingly counter-intuitive
evolution has been explained in terms of the theory of dynamical
balance of excitation and inhibition [1] considered
as one of the major contributions of theoretical physics to
neuroscience. However, this theory has been recently criticized,
because it requires unphysically large external currents,
experimentally unjustified. We propose a balancing
mechanism based on a biologically plausible form of synaptic
plasticity, which works also with weak external currents.
Biologically, the mechanism exploits the plasticity of
excitatory–excitatory synapses induced by short-term
depression [2]. Mathematically, the nonlinear response of the synaptic
activity is the key ingredient responsible
for the emergence of a stable balanced regime. Our claim is supported
by a simple self-consistent analysis accompanied
by extensive simulations performed for increasing network sizes. The
dynamical regime is characterized by highly irregular
spiking dynamics of all neurons as usually observed in the brain cortex [3].

[1] C. van Vreeswijk and H. Sompolinsky, Science 274, 1724 (1996).

[2] M. V. Tsodyks and H. Markram, Proceedings of the national academy
of sciences 94, 719 (1997).

[3] A. Politi and A. Torcini, Chaos 34, 041102 (2024).