Poisson or not Poisson: differences in spike train statistics between parietal cortical areas.

The variability of neuronal responses is proportional to the mean in many brain areas, which suggests that neural responses might follow a Poisson distribution. In this issue of Neuron, Maimon and Assad document a surprising violation of Poisson firing. Specifically, they show that there are differences in the amount of periodic structure in spike trains across cortical areas, with multimodal sensory areas being more regular than visual areas.