A misty-eyed Nancy Reagan participated in a brief dedication ceremony yesterday for the Loyal Davis Neuroscience Center, a 40-bed rehabilitation and research unit in Northwest D.C. named for her late stepfather, a renowned neurosurgeon.

"Every time I'm in a hospital, I can't help thinking of my father . . . the times I went on rounds with him -- the times I watched him work," the first lady told a gathering of patients and staff at the National Rehabilitation Hospital at 102 Irving St. NW.

"And as I look around it means a great deal to me personally . . . to see that my father's legacy is very much alive . . . , " she said, her voice cracking with emotion.

Referring to her work as a nurse's aide in a Chicago hospital during World War II, Mrs. Reagan said, "It gave me a really deep inner satisfaction and helped me realize the importance of giving of ourselves to others."

Also attending the dedication were Mrs. Reagan's brother, Dr. Richard Davis, a Philadelphia neurosurgeon, his wife Patricia and White House Press Secretary James S. Brady.

Before the ceremony the first lady stopped to talk with some wheelchair-bound patients in a corridor and spent five minutes in the room of Mario Andretti Roberts, a District teen-ager paralyzed in a football accident last October. In a Sunday column by Washington Post writer Courtland Milloy, Roberts said he hoped that Mrs. Reagan would visit him so that he could discuss his concerns about handicapped people.

"I'm really worried about handicapped people in the District," Roberts told Mrs. Reagan yesterday. He said that many sidewalk ramps are inadequate and that he has had little help in purchasing special equipment, such as elevators for his house and a van with hand controls, so that he can be more independent.

"I plan to go home in a couple of months, and I want to be as independent as I can," said Roberts, who sat in his wheelchair and was dressed in a blue hospital T-shirt and pants and red tennis shoes.

"We are doing a lot for the handicapped and encouraging business to hire handicapped people," the first lady assured him, before admitting, "I don't know, legally, about the situation . . . "

During the visit, Roberts, who said he was "more fortunate than most handicapped people," pointed to a plaque picturing him in his football uniform. "That's nice. You must be proud," said Mrs. Reagan, rubbing her hand across the inscription, which read: "A tribute to Mario Roberts for outstanding sportsmanship, leadership and dedication to football, from the administrators, staff and junior varsity football team of Dunbar Senior High School."

"I want to say thanks to you, too, because . . . you all sent me a Christmas card and your husband sent me a couple of pictures," Roberts told her. "They brightened my day."

"You'll be able to do a lot," Mrs. Reagan told him. "I do a lot of hospital visiting. It's amazing what people can do . . . "

Roberts smiled broadly. "It amazes me, too," he said. "If you really work at it you can do anything you want to. I've matured a lot since October 31st" -- the date of his injury.

The two posed for a picture, a proud young Roberts straightening his spine and lifting his head for the camera, Mrs. Reagan kneeling beside his chair. She paused to kiss his forehead before leaving the room, and he requested a copy of their photo -- "an autographed one."