SACKS EXPLORES DREAMS, DISORDERS OF MICRONESIA.

Byline: Christopher Lehmann-Haupt The New York Times

Title: ``The Island of the Colorblind''

Author: Oliver Sacks

Data: Illustrated. 298 pages, Alfred A. Knopf; $24.

Our rating: Four Stars

Part of the fun and challenge of reading Oliver Sacks' engaging new book, ``The Island of the Colorblind,'' is pulling together in your mind its disparate elements. ``This book is really two books,'' Sacks begins his preface, ``independent narratives of two parallel but independent journeys to Micronesia.''

Sacks, the author of ``Awakenings'' and ``An Anthropologist on Mars'' continues, ``I went to Micronesia as a neurologist, or neuroanthropologist, intent on seeing how individuals and communities responded to unusual endemic conditions - a hereditary total colorblindness on Pingelap and Pohnpei; a progressive, fatal neurodegenerative disorder on Guam and Rota.''

When he returned to his home on City Island in New York, he eventually saw the ``connection and meaning'' of his experiences and began to write. But he leaves to the reader the task of working out that connection and meaning. Moreover, when he did begin to write, the book began to grow, as he puts it, like an unruly plant.

``Since the offshoots, in volume, now started to vie with the text,'' he writes, he decided to place ``many of these additional thoughts together, as endnotes.'' So as well as making the connections, the reader must also figure out how to read the book: text and then endnotes, or text and endnotes together.

As it turns out, you find yourself switching back and forth, reading the endnotes as they are cited in the text. Remarkably, they prove to be both welcome and not in the least distracting. The narrative drive in each of the two main sections is strong enough in its particular way to give leeway to diversion.

In the first section, called ``The Island of the Colorblind,'' this drive is provided by the interaction between Knut Nordby, a colorblind Norwegian scientist whom Sacks invited along on his Micronesian journey, and the natives of the region who are similarly afflicted.

Total congenital colorblindness, or achromatopsia, is a scary disease in that it not only forecloses all sense of color but also makes its victims painfully sensitive to light.

In Sacks' telling, Nordby lends comfort to those affected, nearly 8 percent of the population, by showing them they are not alone in the world and by presenting them with visual aids such as sunglasses to protect them from the light. The islanders pay back Nordby and his companions by teaching them about their culture and by sharing their lives.

In the second section, called ``Cycad Island'' after the ancient, palmlike evergreens that happen to be one of Sacks' obsessions, the narrative drive is that of a medical whodunit, or, more exactly, a what-caused-it. What accounted for the neurodegenerative disorder that the people of Guam, the Chamorros, call lytico-bodig?

Sacks writes, ``The disease, seemingly, could present itself in different ways - sometimes as `lytico,' a progressive paralysis that resembled amyotrophic lateral sclerosis (ALS, or motor neuron disease), sometimes as `bodig,' a condition resembling parkinsonism, occasionally with dementia.''

It appears to show up in families, which suggests that it is congenital. But it also is disappearing, which implies an outside cause.

A suspect for a time was the author's favorite plant, the cycad tree, whose seed, despite being toxic, is used to make a form of flour the Chamorros call fadang or federico. But the solution to the problem has proved to be complex and elusive.

So given the flow of these narratives, you don't in the least mind pausing to swim up Sacks' tributaries of thought. And the places they take you prove fascinating, whether they are medical arcana, philosophical speculations, literary asides, or quotations from Goethe, Humboldt, Kant, Darwin, Melville, John Updike and John McPhee. You read them avidly and then float right back into the mainstream.

As for what ties the whole book together, the secret is as elusive and complex as in any work of literary art.

But you get some inkling in an autobiographical section near the end, where Sacks recalls his childhood fascination with ancient plants and his night-dreams of ``peaceful, swampy landscapes of 350 million years ago, a Paleozoic Eden,'' from which he ``would wake with a sense of exhilaration, and loss.''

He adds: ``I think these dreams, this passion to regain the past, had something to do with being separated from my family and being evacuated from London (like thousands of other children) during the war years. But the Eden of lost childhood, childhood imagined, became transformed by some legerdemain of the unconscious to an Eden of the remote past, a magical `once,' rendered wholly benign by the omission, the editing out, of all change, all movement.''

To realize these dreams seems in part what drew him to his South Pacific islands.

Of course, they proved no Eden, but instead places of disease and ecological disaster, where, as he writes, on Guam at least, bird life has been wiped out by climbing snakes so numerous that they daily get into the island's transformers and cause electrical failures known as ``snakeouts,'' and where, on Rota, the ``unique forests'' are being destroyed ``on a fearful scale, most especially with the building of Japanese golf courses.''

Still, Sacks' humane inquisitiveness lends a philosophical perspective to every threatening change. His scenes are stills from the moving picture of timeless evolution. And the way his subjects accept their fate redeems his story from gloom, even lending it a certain gaiety.

Typical is his description of how one man suffering from increasing memory loss bid goodbye to him at the end of a visit: ```Come again soon,' he said, cheerfully. `I won't remember you, so I'll have the pleasure of meeting you all over again.' ''

In ``The Island of the Colorblind,'' the reader, too, has the pleasure of meeting Sacks all over again.

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2 Photos

Photo: (1--2) Oliver Sacks examines unusual endemic medical conditions and how Micronesian islanders cope with them in ``The Island of the Colorblind.''