Recently, the search for what he calls "the splinters that make up different attention problems" has taken Castellanos in a new direction. First, he explains that your brain is far less concerned with your brilliant ideas or searing emotions than with its own internal "gyroscopic busyness," which consumes 65 percent of its total energy. Every fifty seconds, its activity fluctuates, causing what he calls a "brownout." No one knows the purpose of these neurological events, but Castellanos has a thesis: the clockwork pulses enable the brain's circuits to stay "logged on" and available to communicate with one another, even when they're not being used. "Imagine you're a cabdriver on your day off," Castellanos says. "You don't need to use your workday circuits on a Sunday, but to keep those channels open, your brain sends a ping through them every minute or so. The fluctuations are the brain's investment in maintaining its circuits online.