O próximo colóquio do Programa de Pós-Graduação em Física da UFPE vai abordar o tema “Criticality of the Brain (Criticidade do cérebro, em português)”, às 16h desta sexta-feira (20), no auditório do Departamento de Física, localizado no Centro de Ciências Exatas e da Natureza (CCEN). O evento contará com a participação do professor Hans Herrmann, do Departamento de Física da Universidade Federal do Ceará, estudioso de dunas e redes complexas. 

Resumo do palestra em inglês

The activity of the resting state of the brain exhibits avalanches of spiking activity of sizes that follow a power-law distribution. I will present Monte Carlo simulations of self-organized and driven models that do reproduce avalanches fulfilling the scaling laws of a general theory for crackling noise. The power spectrum, however, does not agree with this theory. We explain this deviation by establishing a phase diagram involving the fraction of inhibitory neurons and finding that the brain operates at a certain distance from the critical point. In an alternative attempt to grasp brain criticality we investigate the spiking patterns of model generated data as well as in vitro and in vivo neural systems mapping them to a fully connected Ising model with local fields and interaction constants which are obtained by a Boltzmann machine. The distributions of these fields and interaction constants seem to be universal. A Monte Carlo simulation suggests that this Ising system operates at a critical point separating a ferromagnetic from a paramagnetic phase. Finally we will assess the learning capacity of our neural network model by training various logical functions, finding scaling laws in the strength of synaptic adaptation and observing memory loss while learning several functions simultaneously.