Da epidemiologia para a neurociÃncia: entendendo NeurÃnios disparantes acoplados eletricamente atravÃs do Modelo sirs estocÃstico na rede hipercÃbica

AUTOR(ES)

Vladmir Ramos Vitorino de Assis

DATA DE PUBLICAÇÃO

2006

RESUMO

The response function of individual sensory spiking neurons (ring rate vs. stimulus intensity) has a small dynamic range. For example, in olfactory sensory neurons, only ~ 10 dB of stimulus intensity can be reasonably coded, if saturation and low-stimulus noise were to be avoided. This is in stark contrast with the large dynamic range observed in the next synaptic step: the response of olfactory glomeruli and mitral cells can have dynamic ranges twice as large. There is experimental evidence that electrical coupling among neurons (either via gap junctions or ephaptic interactions) could be responsible for this enhancement of dynamic range. In order to evaluate the effect of electric coupling in the collective response of spiking neurons, we study the stochastic SIRS epidemic model on the hypercubic lattice and reinterpret the Susceptible-Infected-Recovered-Susceptible states as Quiescent-Firing-Refractory-Quiescent, respectively. We extend the model recently studied by Jaewook Joo and Joel L. Lebowitz [1] by introducing an external sensory stimulus (which, in the epidemiological context, amounts to a spontaneous infection rate). We perform mean field calculations at the single-site and pair levels, as well as simulations. We show that, due to amplification via excitable waves, the dynamic range grows with the electrical coupling up to a critical value, above which the network presents self-sustained activity. Above criticality, the dynamic range decreases with the electrical coupling because self-sustained activity masks low-intensity stimulus. The largest dynamic range is therefore obtained precisely at the nonequibrium phase transition, providing a clearcut example of optimal processing at criticality. Furthermore, the maximum value of the dynamic range for the d-dimensional hypercubic lattice decreases with d

ASSUNTO(S)

epidemic model modelo epidÃmico criticalidade dynamic range neurociÃncia electric coupling acoplamento elÃtrico neuroscience fisica criticality faixa dinÃmica

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