Communicated by Laurence Abbott Dynamics of Populations of Integrate-and-Fire Neurons, Partial Synchronization and Memory

We study the dynamics of completely connected populations of refrac-tory integrate-and-fire neurons in the presence of noise. Solving the master equation based on a mean-field approach, and by computer sim-ulations, we find sustained states of activity that correspond to fixed points and show that for the same value of external input, the system has one or two attractors. The dynamic behavior of the population under the influence of external input and noise manifests hysteresis effects that might have a functional role for memory. The temporal dynamics at higher temporal resolution, finer than the transmission delay times and the refractory period, are characterized by synchro-nized activity of subpopulations. The global activity of the population shows aperiodic oscillations analogous to experimentally found field potentials.