Book Review
Mind Time: The Temporal Factor in Consciousness
Cambridge, MA: Harvard University Press, 248 pp., illus., index, $29.95.
ISBN: 0-674-01320-4.
The main purpose of this book is ostensibly to summarize and present essential elements of the relationships between the timing of objective neurophysiologic events and the appearance of conscious awareness of sensory inputs and voluntary acts, a subject that Dr. Benjamin Libet has been intensively and productively investigating in human subjects for many years. This in itself would be sufficient to justify the reading of this book, but an added bonus is the fascinating and scholarly way that Libet has extended the significance of his experimental findings to the more esoteric concepts of the conscious and unconscious minds, voluntary behavior, free will, and even the soul.
Consciousness is a property of living things and has, therefore, understandably been a subject of interest to biological scientists for centuries. Because conscious awareness of oneself and one’s environment is so abstract a phenomenon, so unique to each individual, and so far beyond our current knowledge and concepts of energy and matter, that it has also attracted the interest and speculation of those concerned with matters outside the boundaries of the physical world, such as philosophers, theologians, and even spiritualists. It has often been lumped together with comparably abstract, non-physical phenomena, such as reasoning and faith, into the domains of the mind and soul, which have not always been considered to be associated with the brain. For example, the mind and soul were once thought to reside in the Bone of Luz, a mythical bone believed by Mohammed and the Arabs to be located at the base of the spine, probably the coccyx, and by the Hebrews of the cabala at the top of the spine. More recently, psychoanalytical theory and practice found no need to relate mental processes to brain functions and mechanisms. A propos of this, the eminent psychiatrist Leon Eisenberg of Harvard University presented an insightful lecture to the Royal Society of Psychiatry (published in the British Journal of Psychiatry, 148:497-508, 1986) on “Mindlessness and Brainlessness in Psychiatry,” in which he compared the irrelevancy of the brain in psychoanalysis, e.g., “brainlessness,” with the disregard of the mind in recent obsessions with neurotransmitters and their receptors in the brain, e.g., “mindlessness.”
It is, therefore, not surprising that there have been at least two schools of thought about the relationship between brain and mental functions. One school is deterministic or reductionist and believes that mental functions are products of brain functions. It preaches that products of the mind, such as thought, awareness of oneself and surroundings, feelings of love, hate, fear, loyalty, faith, etc., all phenomena currently beyond the known physical and chemical processes within the brain, will, when we learn more about the brain, ultimately prove amenable to scientific experimentation, observation, and explanation. In contrast, the other school, Cartesian dualism, preaches that brain and mind are completely unrelated and belong to different and separate domains, one physical and open to experimental investigation, and the other philosophical, and that matters of the mind, like the soul, are beyond the realm of direct observation of physical and chemical processes. In what other realm they might exist is unclear. Is it a spiritual one? In any case, uncertainties about the nature of consciousness may have intrigued biologists but has generally inhibited them from studying it experimentally and trying to define it in term of known biological processes. For example, several years ago I was asked to participate in a symposium on consciousness by presenting a talk on the Biochemistry of Consciousness. I was initially at a loss about what to say, but, fortunately, recalled Justice Potter Stewart’s statement in the Supreme Court’s decision in 1973 about obscenity. I opened my talk by paraphrasing his statement by replacing the word “obscenity,” with “consciousness;” “I shall not today attempt further to define consciousness, and, perhaps, I could never succeed in intelligibly doing so, but I know it when I see it.” I then proceeded to discuss the biochemistry of unconsciousness, a condition readily associated with and described in terms of disturbances in biochemical and physiological processes in the body and brain.
In this book Libet’s deft interweaving of his own beliefs and research findings with views held by scientists and philosophers over the centuries makes for fascinating reading. The question of the nature of consciousness has seduced many brilliant thinkers, including Descartes, Newton, Pascal, and more recently some Nobel laureates in the biological sciences, such as August Krogh, John Eccles, and Francis Crick. Although never Libet never expresses unambiguously a commitment to either Cartesian dualism or determinism, he is clearly not intimidated by the vague and esoteric nature of consciousness and does tend to support the belief that brain functions and conscious subjective awareness are intertwined. It is, I believe, difficult not to believe this. Although biochemical and electrical processes can persist and memories retained during prolonged absences of consciousness, as, for example, in general anesthesia or coma, there is no evidence of conscious subjective awareness in the absence of cerebral energy metabolism or electroencephalographic activities. The major message of this book is that it is possible to study and characterize some properties of consciousness by studies in the brain with conventional physiological techniques.
Studies of consciousness require intelligible communication between a conscious subject and the investigator. This requirement essentially limits such studies to human subjects in an unanesthetized conscious state. Libet summarizes in this book the results of such truly unique studies that he initiated in collaboration with the neurosurgeon Bertram Feinstein a number of years ago and has continued since then. These were done by stimulating and/or recording electrical activity in defined regions of the cerebral cortex of patients in the conscious state during neurosurgical procedures and correlating the electrical responses in the cortex with the patients’ reports of their first conscious subjective awareness of the event. The results showed surprising discrepancies in the timing of the electrical responses in the brain and the onset of conscious awareness during induced sensory stimulation or conscious voluntary movements. This explains the inclusion of time in the title of the book. Conscious awareness of sensory stimulation lags about 500 milliseconds behind the cortical electrical response, and voluntary movements freely initiated and executed by the subjects were associated with electrical signals in the cortex that preceded conscious awareness of the movement or the intent to execute the movement by 150-350 milliseconds. The delays may possibly be reflecting the additional time needed to process the information contained in the unconscious electrical signals, but in any case, there are unconscious processes going on in the brain before there is conscious recognition of a sensation or a voluntarily initiated muscular activity. If even during a willed motor task unconscious activities precede the conscious awareness of the task, what does this mean with respect to free will? On the basis of these observations Libet considers the possible operation of an unconscious mind that precedes and underlies those of the conscious mind and engages in fascinating considerations of the existence and role of free will. If unconscious processes manifested by the electrical activities in the cerebral cortex precede the performance and the awareness of a voluntarily executed motor movement, is this evidence that the action is actually initiated by unconscious mechanisms and that the conscious awareness is only of the execution of an act initiated and executed unconsciously without control by free will? This raises again the age-old question of whether free will actually exists. Libet believes that it does. He raises the ingenious and provocative hypothesis that there is in the time lags between the onset of the unconscious cortical electrical activity, the conscious awareness of the intent to act, and the execution of the voluntary movement, adequate time for free will to intervene to restrain the completion of the act. In other words, free operates not to initiate but to interrupt and prevent the completion of an action already initiated and underway unconsciously. From thereon we are treated to fascinating extrapolations of these findings to the philosophical and possibly mystical concepts of mind and soul. Included is a clever, imaginary dialogue between the author and René Descartes, the reputed father of the school of dualism between mind and brain, regarding the meaning and significance of the author’s experimental findings.
In this book Libet does not even come close to explaining the fundamental nature of consciousness and mind, and he does not claim to do so. What he does do, however, is to demonstrate conclusively that it is possible to study these non-physical entities with the tools of physiology and to obtain information that characterize in physical terms some of the properties of these esoteric phenomena. Moreover, he presents his case in a very readable and scholarly way, which make this book a pleasure to read. It is a stimulating interplay between philosophy and science about a subject of immense interest.
Louis Sokoloff
National Institutes of Health, Bethesda, MD
Books Received
Carolyn D. Berdanier and Naima Moustaid-Moussa, (Editors).
New York: Marcel Dekker, Inc., 2004, 507 pp., illus., index, $179.95.
ISBN: 0-8247-5430-1.
Handbook of Stress Medicine and Health, Second Edition.
Cary L. Cooper, (Editor).
Boca Raton, FL: CRC Press I LLC, 2005, 410 pp., illus., index, $149.95.
ISBN: 0-8493-1820-3.
Molecular and Cellular Exercise Physiology.
Frank C. Mooren and Klaus Volker, (Editors).
Champaign, IL: Human Kinetics, 2005, 455 pp., illus., index, $89.00.
ISBN: 0-7360-4518-X.
Principles of Exercise Testing and Interpretation, Including Pathophysiology and Clinical Applications. Fourth Edition.
Karlman Wasserman, James E. Hansen, Darryl Y. Sue, William W. Stringer, Brian J. Whipp.
Philadelphia, PA: Lippincot Williams & Wilkins, 2005, 585 pp., illus, index, $89.95.
ISBN: 0-7817-4876-3.
The Scientific Basis of Integrative Medicine.
Leonard A. Wisneski and Lucy Anderson.
Boca Raton, FL: CRC Press I LLC, 2005, 279 pp., illus., index, $89.95.
ISBN: 0-8493-2081-X.