Even when we’re not doing much of anything, our brain’s cortex, or outer mantle, is bustling with activity. In fact, scientists for the first time have detected “avalanches” of cortex activity in awake monkeys at rest. They’ve also discovered that these bursts of synchronous neuronal activity aren’t just random, but rather precisely ordered. Large avalanches are followed by smaller and smaller avalanches, much like the aftershocks of an earthquake. This type of ordering reveals that the normal state of cortex circuitry is at a tipping point: at the edge of instability — like rocks along an earthquake fault. “Mental illness may involve disturbances in this delicate balance, and abnormal avalanche patterns are potentially detectable,” explained NIMH’s Dietmar Plenz, Ph.D. “Being in such a state of instability allows neurons to telegraph information optimally across varying distances and to quickly adapt to new challenges. This makes it possible for the cortex to grow through development and expand through evolution without changes in its architecture.” Plenz and colleagues report on their study of neuronal avalanches online during the week of August 24, 2009 in the Proceedings of the National Academy of Sciences.