BOOK REVIEW / SCIENCE : Treading the Heady Territory of This Brave New World : THE CHEMISTRY OF CONSCIOUS STATES: How the Brain Changes Its Mind; <i> by J. Allan Hobson</i> ;Little, Brown; $22.95, 300 pages

Brain, mind, body, soul: understanding and explaining the connections between them absorbed the attentions of psychologists, neurologists and forensic physicians or “alienists” at the end of the last century. As this century draws to a close, the extraordinary technological revolution in the neurosciences has shattered the visual barrier of the opaque skull: inside it has found not spiritual and physical entities, folding upon each other as the Christian Trinity subsumes three in one, but a single brain-mind.

Experts in imaging have begun to map the entire brain, from the frontal cortex, where much of our conscious thinking occurs, to the brain stem that controls our heartbeats and the movement of our lungs. Other scientists are discovering just as much by examining the brain’s production of the chemicals--neurotransmitters--that regulate our appetites and moods.

Where in this brave new world of molecules and neurons does a psychiatrist trained in the almost quaint school of Freudian psychoanalysis fit? J. Allan Hobson, professor of psychiatry at the Harvard Medical School and director of the sleep laboratory at the Massachusetts Mental Health Center, will tell you--if you have the perseverance to read his new book, “The Chemistry of Conscious States.” He fits in like a betrayed lover, damning Freud for having begun to look for a science of the mind early in his career, only to leap into the fairy-tale world of dreams and sexually based iconographies like the Oedipus complex, thereby wasting the time of so many psychiatrists of a certain age.

“The influence of Freud has held the field back intellectually,” Hobson explains. “Freud’s mistaken notion of how dreams are actually constructed contaminates the rest of his theory of mental life.”

For dreams, as well as the other activities the brain engages in while we sleep, are Hobson’s specialty. He describes his observations in the sleep clinic of both healthy volunteers and patients. To show us how the different stages of sleep reflect and affect the sleepers’ lives, he focuses on two patients.

While both spin illogical scenarios in their dreams, the “healthy dreamer” dreams while she is sleeping, while the “psychotic” one dreams when he is awake, which we call a hallucination. Dreams and hallucinations are actually the same mental phenomenon, Hobson is telling us: only one is controlled by the dreamer while the other is not. The purpose of dreams, he suggests, may be “homeopathic. We have a sleep seizure to avoid a waking seizure. We dream so as not to hallucinate.”

Dreaming, Hobson explains, is one of three brain-mind states. The others are sleeping and waking. During each state the brain releases different chemical neurotransmitters.

Hobson builds a strong case for the importance of healthy sleep habits, and he offers do-it-yourself advice for keeping a sleep journal and taking control of your personal sleep life. He dwells on the role of REM, or rapid eye movement, in mental health. Deprived of REM sleep, people hallucinate and laboratory rats die from infection.

Hobson is most interesting when he describes how to keep a sleep diary, denounces the “myth of Edison,” (that a couple of hours sleep is all we need), and explains what he calls the brain-mind’s role in sleepwalking and controlled dreaming.

However, the book takes a curious turn as Hobson progresses, as if he changed his mind about what it all means as he was writing. He is bemused by the appearance of drugs in the Prozac family.

He prefers to direct the rank and file of patients to learn to use sleep, the “brain-mind’s own resident physician,” by exercising, meditating and taking control. But the success of the Prozac drugs leads him to a conclusion that questions the value of the dream monitoring he spent so many pages describing.

These drugs reduce both REM sleep and the chemical balance it creates. This leads Hobson to the conclusion that it is the chemicals that matter, and dreaming may be only an epiphenomena--whose only value may be entertainment--an otherwise unnecessary experience if we can balance our brain-mind chemistry artificially.