WASHINGTON (CNN) -- Democratic Sen. Tim Johnson of South Dakota opened his eyes when prompted by his wife, said the senator's spokeswoman Friday, but she cautioned that recovery from his brain surgery will take time.

"We live in a 24-hour news world," said spokeswoman Julianne Fisher. "The body doesn't heal that way. It takes time." Fisher said that Johnson "continues to move in the right direction" and that doctors and his family "continue to be encouraged."

Johnson, 59, remain in critical condition after undergoing surgery late Wednesday for a brain hemorrhage caused by pressure from blood vessels that are too close together, a condition known as a congenital arteriovenous malformation.

Fisher said that Johnson had been able to move both sides of his body and had opened his eyes Thursday when his wife, Barbara, asked him to. She said that doctors were expected to release a written statement on Johnson's condition later in the afternoon.