Neuronal avalanches in awake macaque V1 and V4

Abstract

Neuronal avalanches are cascades of synchronised activity whose sizes follow power law. Analyses of avalanches shed light on cortical dynamics operating near a critical point. In awake monkeys, avalanches were found in motor and premotor cortex, where they are invariant to temporal binning, detection threshold and the number of electrodes employed. Whether awake primate early visual cortex, which receives strong structured afferent drive, shares these properties has not been tested. We analyzed a public 1,024-channel resting-state dataset from V1 and V4 of two macaques. In both animals avalanche sizes followed power laws over more than 10-fold range, the exponent scaled with bin width as alpha proportional to delta-t to the power beta (beta = -0.045 and -0.031), and the distributions ended at a cutoff proportional to the number of electrodes analysed. Raising the detection threshold from 1.5 to 4.5 standard deviations (SDs) removed over 99% of events but changed alpha by only 0.02-0.05 per SD, whereas randomly removing the same events destroyed the power law. Per-electrode shuffling abolished all heavy tails. Eye closure shifted alpha, beta and the branching ratio by less than predefined equivalence bounds, far below the reproducible differences between recording sites. Avalanche organisation therefore extends to awake early visual cortex.