A new RAND Corporation study says 320,000 U.S. troops may have suffered brain injuries in Iraq and Afghanistan from bombs, and less than half say they were ever evaluated by a doctor.

The Defense Department is giving the Brain Trauma Foundation $4.6 million over four years to come up with a device that can evaluate a soldier in seconds and is rugged enough to function in Iraq. It’s part of $300 million that Congress set aside for research into traumatic brain injury and psychological health.