Artificial-heart patient William J. Schroeder got out of bed this afternoon for the first time since his stroke three days ago, sitting up in a chair with assistance, a hospital spokesman reported. But doctors were concerned about his emotional state after his recent ordeal.

The exertion of sitting up and talking with his wife, children and grandchildren for an hour left Schroeder tired, spokesman George Atkins said after speaking with Dr. William C. DeVries, the surgeon who implanted the mechanical heart.

That Schroeder was "alert" and "enjoying conversation" with his family, however, appeared to be a good sign after an earlier report that he had appeared emotionally "withdrawn."

At the daily medical briefing this afternoon, three weeks after Schroeder became the world's second mechanical-heart recipient, Humana Heart Institute chief Dr. Allan M. Lansing said he was worried that Schroeder was spending most of his time sleeping or "lying in bed with his eyes closed," responding only when spoken to and showing little interest in activities around him.

"It is almost like an ostrich," said Lansing, who called it a "psychological" reaction rather than a physical problem.

"I believe he will come out of this and be himself again . . . ," Lansing said. "I believe it is temporary." If not, he said, it could further delay Schroeder's recovery.

Lansing said no significant neurological problems appeared to remain since the stroke Thursday night cut off the blood supply to a small portion of Schroeder's brain, leaving him unconscious and temporarily paralyzed on his right side.

By today, Lansing said, Schroeder was "moving everything, speaking appropriately," and his speech was "clearer, not slurred or slowed." Doctors "are very pleased with his physical state," he said.

Lansing said an electroencephalogram (EEG) of Schroeder's brain waves showed no signs of damage to the cerebral cortex, the portion responsible for cognitive and motor functions.

He also said the edema, or swelling, in Schroeder's legs had virtually disappeared, although his blood pressure was up slightly.

But over the last few days, he said, Schroeder, 52, normally an extrovert, "doesn't seem to be interested in talking."

He noted that before the stroke Schroeder was excited about having transmitted to his hospital room a Saturday-night high school basketball game between his home-town Jasper, Ind., Wildcats and the South Ridge Raiders.

But this morning, when Lansing asked whether he wanted to know the score, Schroeder said no. And when asked whether he cared, Schroeder responded, "not really."

Though mood fluctuations are common after a stroke, Lansing noted that Schroeder "has a lot more to be concerned about" than most patients. "It's a distinct possibility it's all caught up with him."

DeVries said he believes that the device was to blame for the stroke, but other causes, such as Schroeder's diabetes, have not been ruled out.

DeVries and Humana, a for-profit institution that is paying for the artificial-heart experiments, have permission to do five more artificial-heart implants and have interviewed other candidates, but Lansing said today, "We have no plans to do anything else until Mr. Schroeder is perfectly stable and we're happy with his condition."