Ricardo Iriart last saw his wife conscious four years ago. Every day since, he has visited Ángeles, often spending hours talking to her in hopes that she could hear him.

Over the last year, he’s gotten a new understanding of his wife’s condition, participating in cutting-edge research into “covert consciousness.” It’s an emerging field of study that probes what patients with disorders of consciousness can comprehend, even when they can’t respond.

Earlier this year, the University of Pittsburgh became the first research institution in the U.S. to use an Austrian device called the mindBeagle in a clinical trial of covert consciousness.