INDIANAPOLIS (AP) _ Stan Fox, who suffered a serious head injury after crashing at the Indianapolis 500, has emerged from a five-day coma and is responding to simple commands.

Fox, who underwent surgery to remove a blood clot from his brain after Sunday's race, was upgraded from critical to fair condition Friday at Methodist Hospital, where he is being treated in the neurocritical care unit.

``Stan is conscious and able to follow simple commands. He has opened his eyes and is more aware of his surroundings,'' the hospital said in a statement.

Fox, of Janesville, Wis., had been unconscious since his car slammed almost head-on into the Indianapolis Motor Speedway's concrete wall and exploded in a violent shower of debris.

``He's making some improvements clinically,'' neurosurgeon Dr. Kenneth L. Renkens said. ``He will now follow some commands with his left hand, so it seems as if he's processing some of the information.

``I think that it's going to take a longer time, a month, to see how extensive the injury was.''

Fox regained consciousness after a series of steps that encouraged the treatment team. The driver responded to stimuli by grimacing a few days ago, then began moving left arm, and on Friday was able to hold up two fingers, Renkens said.

``He started to open his eyes yesterday with some stimulation, which he hadn't done before,'' the doctor said. ``He's still not fully awake and alert. He's still fairly drowsy and not keeping his eyes open all the time,''

Renkens said he could not discuss what part of Fox's brain was injured and could not accurately predict what brain functions could be affected by the injury. He also said it was too early to discuss a prognosis for Fox's recovery.

``Generally, the longer a person is in a coma, the less likely the chance of a full functional recovery,'' Renkens said.

Asked if Fox was now likely to survive the injury, Renkens was cautiously optimistic. ``He should be. There are things that can happen ... unexpected things.''

Fox was still on a respirator to assist with his breathing, but was no longer receiving medication, the doctor said.

The swelling on the brain that concerned doctors earlier in the week has not been a problem since Wednesday, Renkens said.

Fox's brother said the family was encouraged by medical improvement, but remained cautious.

``We are, of course, delighted with this morning's news,'' Fred Fox told the Janesville Gazette. ``But we want everyone to know that this is a long, slow recovery process.''