Veteran insomniacs know in their bones what science has to say about sleep deprivation and pain: that the two travel together, one fueling the other.

For instance, people who develop chronic pain often lose the ability to sleep well, and quickly point to a bad back, sciatica or arthritis as the reason. The loss of sleep, in turn, can make a bad back feel worse, and the next night’s slumber even more difficult.

Why sleep deprivation amplifies pain is not fully worked out, but it has to do with how the body responds to an injury such as a cut or turned ankle. First, it hurts, as nerves send a blast up the spinal cord and into the brain. There, a network of neural regions flares in reaction to the injury and works to manage, or blunt, the sensation.

Think of the experience as a kind of physiological dialogue between the ground unit that took the hit and the command-control center trying to contain the damage. In a new study, a team of neuroscientists has clarified the nature of the top-down portion of that exchange, and how it is affected by sleep.