The neuronal refractory period causes a short-term peak in the autocorrelation function

Autocorrelation functions are a major tool for the understanding of single- cell firing patterns. Short-term peaks in autocorrelation functions have pr eviously been interpreted as a tendency towards bursting activity or elevat ed probability to emit spikes in a short time-scale. These peaks can actual ly be a result of the firing of a neuron with a refractory period followed by a period of constant firing probability. Analytic studies and simulation s of such neurons replicate the autocorrelation functions of real-world neu rons. The relative size of the peak increases with the refractory period an d with the firing rate of the cell. This phenomenon is therefore more notab le in areas such as the globus pallidus and cerebellum and less clear in th e cerebral cortex. We describe here a compensation factor that can be calcu lated from the neuron's hazard function. This factor can be removed from th e original autocorrelation function to reveal the underlying firing pattern of the cell. (C) 2001 Elsevier Science B.V. All rights reserved.