Hidden Consciousness Found in Patients in Vegetative State

One in four people with brain damage who are largely unresponsive are capable of thought, a finding that suggests up to 100,000 US patients diagnosed as being in a minimally conscious or vegetative state have at least some level of consciousness, researchers say. Traditionally, doctors asked patients with brain damage to speak, look in a certain direction, or raise a finger. Fleeting responses might result in a diagnosis as minimally conscious, while nonresponses might result in a diagnosis as vegetative, per the New York Times. But recently, researchers have examined other techniques for determining consciousness, including by looking at electrical activity and blood flow in the brain.

British neuroscientist Adrian Owen is credited with discovering consciousness in a patient diagnosed as being in a vegetative state in 2006, when he asked the woman to imagine herself playing tennis and saw brain activity in the same regions as would occur in individuals without brain damage. In this new, large-scale study, published Wednesday in the New England Journal of Medicine, researchers set out to learn how common this condition, now dubbed cognitive motor dissociation, might be. Teams of neurologists in the US, UK, France, and Belgium asked 241 unresponsive patients to perform complex cognitive tasks, including imagining themselves playing tennis.

Sixty patients (25%) had patterns of brain activity that matched what was seen in healthy people who performed the same tasks. This suggests a similar rate of US patients diagnosed as in a minimally conscious or vegetative state might be capable of thought and might even be able to communicate with a brain implant. Dr. Nicholas Schiff, one of more than 50 study co-authors alongside Owen, urges better exams for people with disorders of consciousness, noting the study probably underestimates the share of patients capable of thought, per Nature. He notes the test sets a high bar for registering brain activity, and only 38% of 112 responsive patients with brain damage showed consistent brain activity. (More brain damage stories.)