Why You Might Want Your Brain at the Very Edge of Chaos with Keith Hengen

A human brain contains 86 billion neurons, each connecting to thousands of others in a network more complex than the entire internet (by far). This biological computer can learn new skills, form memories, and adapt throughout your lifetime. How does it work? Why doesn’t it overload or burn out? How can a brain work just as well in medieval Norway as it does in modern Tokyo? We think that the answer lies in a concept borrowed from physics called "criticality”. This is the same mathematical principle that explains how water turns to steam and how avalanches spread down mountainsides. All of these systems suddenly become interesting when they’re at a "tipping point”, testing just on the edge of chaos.

At criticality, the brain exhibits remarkable properties: it can process information across all time scales simultaneously, from split-second reflexes to long-term memories. Small changes can cascade through the network in patterns that look surprisingly similar to avalanches, forest fires, or earthquakes – all following the same mathematical rules that physicists have studied for decades.

In this talk, I’ll explore how neuroscientists measure these "neural avalanches" using everything from tiny electrodes to brain scanners, and what happens when the brain drifts away from this optimal state. Our evidence suggests that criticality is necessary for learning, the purpose of sleep is to restore criticality, and many brain disorders – from Autism to Alzheimer's – are defined by departures from this criticality. This discovery suggests that, despite their biological complexity, brains may follow surprisingly universal physical principles. Understanding these rules is transforming how we think about learning, sleep, and brain health across the lifespan.