Up

Previous

Next

Nicolas Fourcaud, David Hansel, Carl van Vreeswijk, and Nicolas Brunel

Neurophysique et Physiologie du Systeme Moteur - CNRS - Universite Paris 5 - France

In sensory systems, neuronal populations have to track rapidly fluctuating inputs. We explain here how ionic current dynamics leading to spike emission is a limiting factor of this ability. Previous analytical studies have investigated the response of the instantaneous firing rate of the leaky integrate-and-fire (LIF) model to noisy oscillatory inputs at high frequency f. The firing rate temporal modulation A(f) decreases as 1/sqrt(f) with a phase lag L(f) of 45 degrees in presence of white noise while it stays finite with no phase lag with temporally correlated noise. In contrast, numerical simulations of several conductance-based models reveal a different behavior: A(f) decays as 1/f and L(f) tends to 90 degrees. To explain this qualitatively different behavior, we introduced and analytically investigated a family of 1-variable models which incorporate active properties. The 'quadratic' integrate-and-fire neuron, which describes the subthreshold dynamics of a large class of neurons near the firing onset, is a particular model in this family. However, it cannot account for the 1/f behavior: A(f) decays as 1/f