I'm guessing they mean grenades, artillery, rockets....anything that 'thumps' the whole area, including the brain. Even the sustained concussion of a heavy mach

I'm guessing they mean grenades, artillery, rockets....anything that 'thumps' the whole area, including the brain. Even the sustained concussion of a heavy machine gun might be a heavy enough vibration to cause some inflammation, although I'd hope DARPA had long ago tested that theory.