Terry Wallis, who spontaneously regained his ability to speak after a traumatic brain injury left him virtually unresponsive for 19 years

And who then became a subject of a major study that showed how a damaged brain could heal itself, died on March 29 in a rehabilitation facility in Searcy, Ark. He was 57.

He had pneumonia and heart problems, said his brother George Wallis, who confirmed the death.

Terry Wallis was 19 when the pickup truck he was in with two friends skidded off a small bridge in the Ozark Mountains of northern Arkansas and landed upside down in a dry riverbed. The accident left him in a coma for a brief time, then in a persistent vegetative state for several months. One friend died; the other recovered.