NEW YORK -- "I had a dream about manganese the other night," says Oliver Sacks, chortling over the idea. "I can't think of all the details, but I felt so good when I woke up.

"It was a dream about a stable mental object," he continues with delight. "You know, people may come and go, but manganese is forever. Its electrons behave themselves. They've got Pauli's exclusion principle. They can't leave orbits. You know where you are with manganese."

As a source of inspiration for dreams, the periodic table of elements isn't exactly standard. But for writer-neurologist Sacks, it's a natural.

A shy, burly Santa Claus of a man, Sacks, 57, is a consummate scientist, a compassionate clinician. He is also the model for the brilliant, caring doctor whose work with seemingly hopeless patients in a Bronx hospital for the chronically ill is described in the new movie "Awakenings."

And today, huddled self-protectively at his desk in his office in a Greenwich Village apartment building, he is not at all comfortable with finding himself at the wrong end of a microscope. "Celebrity is not a word I use or a concept I'm very interested in," he says.

He has been avoiding the spotlight all his life, preferring instead to define himself through his work with communities of outsiders: the strangely "frozen" post-encephalitic patients described in "Awakenings"; the neurologically damaged ones he detailed in "The Man Who Mistook His Wife for a Hat"; the deaf culture he wrote about in "Seeing Voices." He works with them, studies them, and then, through his best-selling books, interprets their worlds to the world at large.

It is with these people whom society has shunted aside that Sacks is more at ease. An erudite, expressive man, he is not married. He lives alone. "I feel I don't have any identity," he says simply. "I'm a resident alien, a kindly resident alien."

So it was with considerable trepidation that Sacks approached the personal exposure involved -- both for him and his patients -- in seeing his 1973 book translated to the big screen. (He is the film's technical consultant. The screenplay was written by Steven Zaillian.) His book -- essentially a compilation of case studies from the spring and summer of 1969 -- had been adapted many times before, as a documentary film, a radio drama, a stage play, a one-act play by Harold Pinter. But the idea of a flat-out commercial film with mega-movie-stars Robin Williams and Robert De Niro at first was disturbing.

"I was worried about the relation of fact to fiction -- particularly the fictional me," says Sacks, his voice still full of stammers and the accent of an upper-class English Jewish childhood. "I wondered very much if it was possible to act a neurological disorder.

"I finally decided that the plot and character and story were not quite my business but that representing neurological and medical and historical reality was. As long as I could imagine it, it was okay."

In the fall of 1989 while the film was being shot, Sacks traveled to the Brooklyn set at 6:30 every morning before starting his ordinary workday. The company members took him to their hearts. "Oliver was invaluable," says director Penny Marshall. "If we had any medical questions at all, I would turn to him and say, 'Would this happen? Is this okay?' and he'd say, 'Well, maybe a little more like that.' Robin and Bobby both loved talking to him. He was terrific."

What allowed Sacks to relax a little was his decision not to allow his name to be used (his character, played by Robin Williams, is called Dr. Malcolm Sayer). And by Williams's ability to observe him unobtrusively, in order to incorporate some of the doctor's mannerisms in his performance. Says Sacks, "Robin was infinitely tactful and never gave me a feeling of watching me. I think he has created a credible, real person. Who is not me."

No Happy Endings "I wanted happy endings," says Sacks wistfully.

They were not to be.

Sacks first discovered the patients whose poignant odyssey is chronicled in "Awakenings" in 1966 at Beth Abraham Hospital, a chronic care facility in the Bronx. Frozen in a variety of physically distorted, trancelike states for decades, they were all victims of an international outbreak of encephalitis lethargica (familiarly known as sleeping sickness) in the years after World War I. Thought to be retarded, mad or simply undecipherable medical puzzles, they had been stashed away, forgotten.

Young Sacks, Oxford- and UCLA-trained, saw a similarity in his patients' symptoms and those of Parkinson's disease, and was intrigued by the possibility of trying out L-dopa, a new drug that had been helpful to victims of Parkinson's. For two years he hesitated.

"Partly I didn't know what would come out of it -- they were so complex physiologically," he recalls. "And partly these patients had been so out of the world, so turned away from the world, I didn't know how bearable it might be for them. I didn't know what sort of Pandora's box would be let out."

The hot New York summer of 1968 made his decision for him. There was no air conditioning, and many of them died. "I thought, Ollie, you'll spend a lifetime procrastinating and hesitating, and the rest of these poor patients will die."

He administered the drug, first on one (played by De Niro), then gradually on the others, and found that, miraculously, it woke them up. But the awakenings were of limited durations. In some cases sooner, in others later, things started to go wrong and the L-dopa produced a tic-ridden manic behavior, even with reduced doses. When taken off the drug, the patients returned to their former state. And each one responded to the drug -- and to its inevitable failure -- differently.

Sacks was despondent. Between March and July, although his apartment was only 100 yards away, he spent 20-hour days at the hospital, trying to stabilize the patients. "I wondered what the hell had I got them into," he says. "I couldn't understand the fluctuations and I didn't know what to do. I worried that I was doing something wrong."

But those concerns were medical. It was the ethical side that really tormented him. The L-dopa experience had caused the patients great suffering. "Did I have the right to meddle," he remembers asking himself.

The patients asked that question too. Says Sacks, "One or two of them said to me, you open the window and you raise unbearable hopes and prospects. And now you close it."

Traumatic Childhood The reliability of science was what had attracted Sacks to it in the first place. As a child in London, he'd been separated from his family and sent away to boarding school to avoid the dangers of World War II. He rarely saw his parents or knew when he would see them next. To make matters worse, he remembers the couple who ran the school as "a disturbed pair, abusers."

Whatever the impact of the situation ("I probably have something of a traumatic sort of blur about the period, which years of analysis haven't dissipated," he says), he connects his desire for stability and predictability to the experience.

"All I can be certain of," he recalls, "is that when I returned to London a month short of 10, I almost immediately developed a passion for science, and in particular for chemistry and the periodic table."

And for numbers. Unlike the location of the first bubble in a boiling liquid or the variations in the flow of water from a tap, numbers were predictable. "As a child I would feel numbers as my friends," he says. "They wouldn't deceive or slip away."

His interests seemed natural to his parents, both doctors: his father, who had given up academic life to become the Yiddish-speaking general practitioner in London's East End in the 1920s, and his mother, a professor of anatomy who was the first woman to be allowed to join the Royal College of Physicians and Surgeons.

Sacks seems to share both parents' skills, the humanity of his father (who died last summer at 94 after having spent the previous four years making daily house calls via taxi), and the acuity of his mother (who died in 1972).

He refers to both as "medical storytellers." His father, who he estimates probably saw more than 100,000 patients, could recall family medical tendencies for generations back. And his mother reveled in sharing her ideas. "She loved telling stories to everyone, the butcher, the milkman," says Sacks. "She didn't have two forms of discourse. Whether it was the colleague or the gardener, the same sort of narrative was given to both."

Sacks's destiny seemed fixed. By 1958, he had gotten his medical degree and was on his way to a series of internships. His father wanted him to join his practice. Not knowing quite what he was going to do next, Sacks found himself "between continents and between lives." Then in 1960, he came to Canada and the United States for a holiday, and soon after he arrived sent home a one-word telegram: "Staying."

He is not sure what he meant by it. "I wished not to belong, and I wished to belong," he ventures. In any case, he had promised himself California. So, putting away "the soft European name of Oliver," he headed west, where, embracing his legitimate middle name, he became Wolf Sacks, the "lycanthropic creature of the freeways." Tall and lean, his hair slicked back, riding a motorcycle. For a time, he was an unofficial physician to a chapter of the Hell's Angels.

From the fall of 1960 until the summer of 1961, he was footloose. With the arrival of his green card (he'd applied for it when he came to America), he became employable, and continued along the neurological path that led him from California hospitals to the patients at Beth Abraham.

"It was a complete accident I went to work with post-encephalitics," he says. "But we were made for each other."

Criticism and Chaos In the summer of 1970, in a letter to the Journal of the American Medical Association, Sacks published his findings on 60 patients he had maintained on L-dopa (sometimes on, sometimes off, sometimes combined with other drugs) for more than a year. The letter explained that all of the patients had done well at first, but then all of them got into trouble. He had found no easy way of controlling or predicting their reactions though the condition of many of them improved.

His letter caused a furor. An entire issue of JAMA was devoted to letters Sacks describes as "abusive."

"I was publicly roasted," he says. "I think a lot of my colleagues really felt threatened by notions of uncontrollability and unpredictability that reflected on their own power and reflected on the power of science."

He was wildly upset. "I'm a genuine neurologist and observer," he says. "And these were my patients. I cared for them, and I passionately wanted things to be right. And if they couldn't be right, I at least wanted them to be intelligible." Sacks wrote to each of the respondents, asking them to come to the hospital and see the patients for themselves. None of them came.

Over the years, as he turned his attention to other subjects, he has continued to treat post-encephalitic patients. And continued to brood over the question of what went wrong.

And now a major motion picture has brought his work to the public. Does it give him a feeling of vindication?

It's a question he avoids answering directly. Instead he points to an international conference on Parkinson's that was held in Rome last summer. He was asked to open the conference by presenting his most recent theories on the subject, which have evolved from some of the concepts of contemporary chaos and catastrophe theory.

He describes his report as "an attempt to model many different factors simultaneously in a way somewhat similar to weather forecasting -- weather forecasting itself being an interesting example of a kind of chaotic system," he says. Factors such as "the absorption of L-dopa from the gut, the way L-dopa is treated in the bloodstream, the levels of dopa in the perceptors in the brain and an attempt to put everything together instead of trying to seek an increasingly elusive relation between just two things like dose and response."

"What I did do was to introduce this chaos theory thing which tried to embrace what everyone was doing," he says. "And I didn't want to do it in a retaliatory way.

"But myself, I'm rather pleased that 20 years later, in clumsy terms, I'm able to have an attempt at some sort of model or theory."

Does he still feel a need to explain what happened?

"I think it needs to be explained," he says. "But it is currently not in my power to go any farther than I have."

Has he ever regretted using L-dopa in the first place?

"Not at all," he says briskly. "I regret we didn't have it sooner. For many of my patients it made the difference between living and not living."

Resident Alien Oliver Sacks really is a resident alien. He has maintained that legal status since he came to the United States in 1960. And since 1967, he has been based in New York, where he lives in a red-shingle house on City Island, a mostly working-class, waterfront enclave of the Bronx. He spotted the house and its pleasant gazebo while he was swimming around City Island one day. (He is a champion swimmer.)

He hates the city. He loves open spaces, and the most he can do in New York is walk in the Botanical Gardens, which he tries to do every day.

"I don't know how I ended up in New York," he says. "For years it didn't matter. I was absorbed in my work and thought, and I hardly noticed where I was."

If he is no longer at home in England or New York or California, he is at home with his patients, whether they are deaf or neurologically damaged or Tourettic (he is hoping to get going on a "an endlessly incubated and procrastinated book on Tourette's syndrome") or post-encephalitic.

"I wanted to be one of the patients, to be among them, to be both a participant and an observer," he says of the group he awakened. "It has to do with community and identity. I wanted to know more and more what it was like to be them, to actually know what it felt like to have the sensations."

It affected him with the deaf too. And with Touretters. "I'm an honorary Touretter, one of the few they can bear to be with."

Not everyone welcomes him at first, this large, bespectacled, bearded man in a short-sleeved shirt and seersucker trousers -- he gets overheated easily -- looking for a group of patients to immerse himself in.

"I think originally the deaf community was quite suspicious," he laughs. "Who is this weird person? Where does he come from? What does he want? What does he have up his sleeve? Well, I don't have any sleeves. And I don't want to do any more than try and understand them to some extent."

"There are a million people with chronic neurological disease locked away in this country," he says. "They are sort of dismissed and regarded as defective. But it isn't so. I've been in their world myself for a quarter of a century and I find it full of unexpected life and resource and courage and humor and just the sheer capacity to survive -- and often without bitterness."

A few years ago Sacks was introduced to a new post-encephalitic patient who had been brought to Beth Abraham. She had been in a state hospital for 45 years. "Somehow, and I don't know why," he says, "I looked at her and I wanted to kiss her and embrace her because she was post-encephalitic. I thought, 'you dear old thing.' "

What is there about these patients that attracts him so much? Why build his life around them?

"I'm not sure," he says, venturing that his choices must have something to do with his ambivalence about belonging, and identity, and being an outsider, and his feeling that for him, his way is the safe way, the way he needs.

"And yet sometimes," he says, "I have an image of myself as a little boy with my nose pressed against the window, looking in. I sometimes feel like a sort of Martian. But then I'm a resident alien, you see. Looking in."