Propagation of Neuronal Avalanches (A and B) Probability distribution of the projection of the velocity vector into the coronal (x-y) plane of the brain, , for two representative datasets (A, dataset 1; B, dataset 2). The probability density is shown in color scale. (C) Probability distribution of the direction of propagation in the coronal (x-y) plane, , for each dataset. (D) Left: distribution of velocity magnitude. Right: differences in median velocities of the avalanches during periods of spontaneous and the stimulus-driven activity. ∗p < 0.001, two-sided Wilcoxon rank-sum test. (E) Left: probability distribution of the distance traveled by the neuronal avalanches. Right: differences in median distances of the avalanches during periods of spontaneous and the stimulus-driven activity (p > 0.05, two-sided Wilcoxon rank-sum test). (F) Locations of the initial centers of mass (i.e., ), of neuronal avalanches projected on the coronal (x-y) plane of the brain (for dataset 1). Each green dot corresponds to an avalanche. Note that the vast majority of the initiation sites occurred in the neuronal somata rather than in the neuropil (dense white regions). (G) Probability distribution of the number of simultaneous avalanches, , normalized by its mean , for each dataset (solid lines). The narrow distributions are the expected Poisson distributions given . (H) Probability distribution of detecting two simultaneous avalanches with CMs separated by a distance d, for each dataset. Points indicate distance bins for which the probability of simultaneous avalanches is significantly (p < 0.01) higher than chance (i.e., randomized data; see STAR Methods).