THE MAN WHO MISTOOK HIS WIFE FOR A HAT AND OTHER CLINICAL TALES by Oliver Sacks (Summit: $15.95; 233 pp., illustrated)

Hope and compassion echo through this remarkable collection of case-histories in which the neurologist Oliver Sacks explores the mysterious worlds of his patients. An essayist on a par with Lewis Thomas and Stephen Jay Gould, Sacks is fascinated by the complexity of the human brain. While acknowledging that the brain processes information in many ways like a computer, he perceives that it is more than that. He explains that a successful physician has to understand that “our mental processes, which constitute our being and life, are not just abstract and mechanical, but personal as well--and, as such, involve not only classifying and categorizing but continual judging and feeling also.�

Describing what at first glance seem a veritable freak circus of impaired individuals--autistic twins who communicate by factoring numbers faster than all but the most up-to-date computers, a woman who has lost contact with and can no longer feel her body, a man with amnesia so profound that he cannot remember what has happened to him five minutes earlier, Sacks probes these defects to discover the essential humanity, the soul of the individual beyond the defect.

We meet Jimmy G, a patient suffering from retrograde amnesia--the inability to remember anything at all after, in his case, 1945. We share Jimmy’s bewilderment and frustration at being trapped in a changeless present; and we rejoice with the physician as he glimpses Jimmy in the chapel totally absorbed in taking communion. Jimmy’s spirituality reminds Sacks that a man is more than mere memory.

Again Sacks confronts us with insight into the human condition as we meet an autistic artist who, unable to communicate with other people or learn in a conventional manner, can nonetheless sketch delicate botanical renderings. Sacks finds a parallel between the artist and the genius: Both mental prodigy and mental defective are out of step with the rest of us. The poet John Donne was wrong, Sacks asserts, when he wrote that “no man is an island.� The autistic human being is an island, unconnected with the mainland of humanity, but nonetheless still human.

Sacks ponders the medical nature of these afflictions through the writings of his personal heroes, the giants of neurology Hughlings Jackson and A. R. Luria. He also appreciates the contributions that many of his patients have made to an understanding of their own conditions.

Fascinating for the spectrum of neurological anomalies, in the long run, these Clinical Tales are particularly satisfying because we are privileged to be in the company of an especially compassionate and learned physician.