Scaling Limit of a Generalized Contact Process

We derive macroscopic equations for a generalized contact process that is inspired by a neuronal integrate and fire model on the lattice Z^d. The states at each lattice site can take values in 0 , … , k. These can be interpreted as neuronal membrane potential, with the state k corresponding to a firing threshold. In the terminology of the contact processes, which we shall use in this paper, the state k corresponds to the individual being infectious (all other states are noninfectious). In order to reach the firing threshold, or to become infectious, the site must progress sequentially from 0 to k. The rate at which it climbs is determined by other neurons at state k, coupled to it through a Kac-type potential, of range γ^{- 1}. The hydrodynamic equations are obtained in the limit γ→ 0. Extensions of the microscopic model to include excitatory and inhibitory neuron types, as well as other biophysical mechanisms, are also considered.