There is a special quality to books in which a gifted and successful scholar summarizes a life of work in a chosen field, and Consciousness exemplifies this genre perfectly. Neither scientist nor artist can stand back from work in progress and view it as part of the whole, whereas the sense that one’s days in the atelier are numbered allows the formation of a Gestalt that can be appreciated and perhaps communicated as such to others. In a book beautifully produced for the mass market, Hobson has done just this.

First and foremost a student of sleep physiology, Hobson recognized early that the hallucinatory experience we call dreaming itself involved conscious thought and declared that no theory of consciousness could be considered valid unless it encompassed the form and logic of dreams. An immense number of studies led to a simple and elegant conclusion that I will try to summarize very briefly. As we fall asleep, changes occur in three realms of brain function. Hobson describes these as 1) a decrease in the general level of activation throughout the brain, 2) a shift in the ability of the brain to take in information from outside the individual toward the ability to derive information from memory as an internal source, and 3) shifts in the modulation of neuronal firing resulting from alterations in the secretion of norepinephrine, serotonin, and acetylcholine. He has devised a marvelous cube to represent these three axes, and he uses it to show how waking consciousness, nondreaming sleep, and dream consciousness are related. Activation, modulation, and the ability to process sensory data are at their lowest in non-REM sleep and highest when we are awake; during the dreams associated with REM sleep all three modalities are at the midpoint of their scales and thus the center of his cube.

One of the most intriguing segments deals with "PGO" waves, powerful rhythmic impulses that travel from the pons (P) to activate the geniculate body (G) and into the occipital lobe (O) and thus favor the visual imagery we know so well from our own dreams. PGO waves arise during REM sleep, radiating also into the limbic system and the amygdala. Hobson suggests that the emotions experienced during dreams may implicate such a circuit, and he reminds us that what we feel and see ourselves doing during dreams does not involve actual bodily action because the motor nerves of the spinal cord become depleted of neurotransmitters and are therefore effectively inhibited. When awake, we are aware of our movement and actions because every motor command is reported both to the motor output nerves in the spinal cord and to the sensory centers, whereas in dreams we "know" what we are doing because only motor output is precluded.

Few readers will find this book anything but fascinating. Some examples: Hobson’s summary of the shift from external to internal sources of data explains beautifully the phenomena common to those of us who try to muddle through tasks in blatant disregard of sleep hygiene. One personal benefit derived from Consciousness is that I’ve learned to nap instead of read when the kind of silly thoughts most often experienced during dreams intrude to remind me that I am drowsy. Because thalamocortical circuits are turned off in non-REM sleep, and since we can’t remember what hasn’t entered consciousness, unless awakened during that phase we cannot recall anything that goes on then. PET imaging studies show that dream consciousness requires activation of the limbic structures responsible for emotion, show that the temporal lobe areas known to store emotional memory are also turned on in REM sleep, and "support the hypothesis that emotion has a primary role in determining the content of dream consciousness" (p. 152). Strangely, even though Hobson states clearly that the elaboration of thought and plots during our dreams seems entirely derivative of affect physiology, he suggests neither why this might be so nor what triggers the affect.

Good science sometimes requires careful and forceful exclusion of apparently distracting ideas and data, and the author’s neglect of the psychology of affect in favor of his fervent interest in consciousness is a reasonable but unfortunate example of this tradition. Increasingly, many of us have come to share the understanding that affect is the doorway to consciousness because, whether we are awake or dreaming, nothing becomes the subject of our attention unless first illuminated by the spotlight of an affect. This concept was introduced by Tomkins R1585BABJIJBE, R1585BABCBHBC and has become increasingly important in the past decade as others have begun to study that body of work. Hobson shows photographs of his own sleeping infants and suggests that "their well-organized facial expressions suggesting pleasure, happiness, fear, doubt, and even anger" cannot be considered real emotions because they did not have "anything to do with the environment" (p. 99). That innate affect can represent a programmed reaction to gradients and densities of stimuli that emanate as easily from inside or outside the individual is not considered, and the informed reader is left to guess that Hobson favors the 19th-century James-Lange hypothesis that an organized perception must precede an affect. He doesn’t like the affect distress-anguish: "our [infant] twins cannot…develop strategies to avoid the disgrace of crying" (21); interest-excitement is misidentified as "attentive waking" (175); the effect of surprise-startle as a reset button for whatever had previously occupied consciousness is explained as the work of PGO waves with no understanding that it is an affect.

Throughout this book one can see that each of the innate affects opens its own doorway to the beautiful little cube that has become Hobson’s model for consciousness. His use of this model as an explanation for the many and varied alterations of consciousness seen in clinical syndromes characterized by abnormalities of affective function would work much better were these concepts of affect introduced.

No one can study everything, and few have studied both sleep and consciousness as well and as thoroughly as J. Allan Hobson. This is an important book that brings together information from a lifetime of excellent research and rewards any reader willing to learn just enough of the language of neuroscience to understand and accept what is offered here. I recommend it wholeheartedly.