WASHINGTON (AP) — When people have a brain injury so severe that they can’t squeeze a loved one’s hand or otherwise respond, there are few good ways to tell if they have any lingering awareness or are in a vegetative state. Now researchers have created a tool to peek inside the brain and measure varying levels of consciousness.

The work reported Wednesday is highly experimental, not ready for bedside use yet — and if it pans out, a big question is how to use it without raising false hope. No one knows what level of consciousness at a certain point after injury really predicts recovery.