What is a neuronal avalanche, and what does its power law say about the cortex? · Grey Matter

An avalanche is a burst of activity that spreads across a group of recording sites and then stops, preceded and followed by quiet.

What is a neuronal avalanche, and what does its power law say about the cortex?

An avalanche is a burst of activity that spreads across a group of recording sites and then stops, preceded and followed by quiet. In slices of rat cortex Beggs and Plenz found that avalanche sizes follow a power law with exponent about −3/2 and durations one with exponent about −2, the values expected for a branching process in which each active unit triggers on average exactly one other. That means activity is balanced at the edge between dying out and growing, which is the critical point. Since the balance of excitation and inhibition sets how many units each event recruits, weakening inhibition pushes avalanches toward large, runaway events and strengthening it makes them fizzle.