BOOK REVIEW / NONFICTION : Chronicling Bends and Twists of the Mind : AN ANTHROPOLOGIST ON MARS: Seven Paradoxical Tales <i> by Oliver Sacks</i> ; Alfred A. Knopf $24, 328 pages

Here we are again with Oliver Sacks, the compassionate neurologist who reminds us with each collection of case studies that there is nothing as fascinating or as hard to categorize as the human mind.

This time around, Sacks had coined the word “neuroanthropologist” to describe his field trips away from the hospital to observe the subjects of these tales in their natural habitats.

As he travels, we get to know about Sacks in his non-clinical mode: He can’t resist a chance to swim, even in a cold mountain lake near a dam. We learn about his British family, where his mother was a surgeon and his brother and father general practitioners. It is to his father, in fact, that we owe these seven tales because it was his father’s legacy, on turning 90, to continue making house calls even as he limited his practice.

“An Anthropologist on Mars” is about a special kind of house call. Special because most of the people Sacks visits are not his patients. He goes to learn from them, not to treat them. He learns how a doctor afflicted with the involuntary movements of Tourette’s syndrome can be a brilliant surgeon, how an artist continues painting after being suddenly struck colorblind, and how an autistic scientist is a successful teacher.

Three of the tales are about artists whose works accompany and highlight the text. Stephen Wiltshire, in London, became a best-selling illustrator when he was only 13, and went on at 16 to become a musical prodigy as well. His accomplishments and behavior lead to a discussion of so-called “idiot savants,” because Stephen is autistic.

Stephen reminds Sacks of “Blind Tom,” a teen-age Alabama slave who could not speak or walk until he was 6, and who at 11 played the piano for President Buchanan. Sacks diagnoses Tom’s condition as autism too, a condition unidentified in Tom’s lifetime and only named in the 1940s.

Franco is a different kind of artist. A chef by vocation, he paints astonishingly realistic pictures of his native Tuscan village in his spare time. Sacks matches these pictures against the Italian original and interprets their uncanny verisimilitude as what a colleague calls the “aesthetic crystallization of nostalgia,” nostalgia raised to the level of art and myth. This makes sense, but not in terms of the conventional map of the brain.

Sacks does understand the neurological problem that beset Mr. I., a professional artist whose career was checked when a traffic accident left a lesion in his brain that made him “acromatopsic”--unable to see colors. At first Mr. I. was so depressed by the milky white and black world he faced that he could neither eat nor paint. His livelihood returned with his appetite, however, as he lost even the memory of color.

The question of vision is central to the case of Virgil who could not even comprehend pictures when, after 40 years of blindness, his sight was restored. Blind since 10, Virgil had trouble adjusting to seeing things he had previously known by touch. Like other people who are known to regain vision after almost a lifetime of blindness, he did not understand shadows and had trouble estimating depth and distance. Sacks explains that the cortex of an early blind adult has already become adapted to organizing perceptions in time and not in space. Virgil’s brain could do some adjusting, but he was beset by a conflict of perceptions.

As he began writing this book, Sacks himself was suffering from an injury that incapacitated his right arm. As he managed to adjust to using his left hand, he was reminded of the brain’s ability to find new pathways when something goes awry.

When whatever has gone awry seems to be congenital, like autism and perhaps Tourette’s syndrome, the neural mechanisms are profoundly different from what underlies normal people. He points out that when Stephen’s remarkable talents appeared, they were complete and never childlike.

He concludes with a visit to Temple Grandin who teaches animal behavior at Colorado State University. She is autistic but able to explain what it is like to be unable to connect emotionally with other people. Most important, she is aware of her difference and has declared, “If I could snap my fingers and be non-autistic, I would not--because then I wouldn’t be me. Autism is who I am.”

One of the pleasures of reading Oliver Sacks is recalling his earlier collections and fitting these case histories in with the others. Sacks has modified some of his views in the light of neurobiological information revealed by new scanning and pharmaceutical techniques.

But he is as fierce as ever in the conviction that people who are not normal are who they are, valuable to themselves and the rest of us and able to contribute enormously to philosophy as well as biology about the variety of experiences that makes us all human.