Customer Reviews

Consciousness ('scientific American' Library)

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"Consciousness" is written by a leading sleep researcher, and his discussion on the different brain states of consciousness--awake, non-REM, and REM sleep--are lucid and informative. The answer to the old question of "how do you know you're really not dreaming when you're awake" is answered here. His "conceptual model of conscious states" using the three factors of activation, information source, and modulation is interesting as well. Less successful are his frequent digressions into personal introspection, accompanied by speculation about the internal brain processes that gave rise to them. Nonetheless, overall I found the book well worth reading (speaking as a neurologist) and I imagine the general public will find much of interest here.

I personally like Hobson's work on consciousness. In this volume, he expands, although not greatly, on his earlier views on the matter. (laid out on "The chemistry of conscious states")
The core model is the AIM model, standing for activation, internal or external information, and neuromodulation. In his tridimencional space model, he considers these factors to be able to explain everything about consciousness. This is where I start disagreeing. It is true neuromodulators influence consciousness, but they are not the neural correlates of consciousness. That is, they alter modes of processing, but are not the process itself. Hobson's strong points are in the area of dream research. Dream as delirium is a very convincing piece of theorizing. The phenomenology of dreaming and its relationship to brain waves and the AIM model is clear enough, but not the same can be said of consciousness. I would posit that the AIM model is more of a model of altered states of consciousness that consciousness per se. However, it is also true that theories of consciousness that ignore the powerful influences of neuromodulation must be neceseraly incomplete. This is a must read for anyone in the scientific debate of consciousness, because amongst the pages of this book great framework-type-knowledge arises.

Review of Hobson, J. Allen (1999): Consciousness. Scientific American Library: Distr. by W.H.Freeman & Co., New York.. ISBN 0-7167-5078-3

Dr. A. R. Dickinson. Dept. of Anatomy & Neurobiology Washington University School of Medicine Box 8108, 660 S. Euclid Ave. St. Louis, MO 63110, USA. ...

Hobson provides a welcome and scholarly contribution to the literature concerned with explaining the phenomenon of human consciousness. A most fitting extention of his earlier studies of sleep, dreaming and waking, this new volume also includes discussion of abnormal states of consciousness in the context of a coherent functional account of brain activity. In this sense, Hobson's choice remains essentially reductionist, whilst claiming appeal to combine emergentism, holism and subjectivism. Indeed, he quite rightly asserts that it is this very subjective nature of what we call ‘consciousness', that we are needing to explain. There are no clear answers to the question of how and why we generate the particular contents of conscious expeience ‘chosen' by the brain mind (cf Edelman & Tononi, 2000), but we are provided with a rather appealing neurally-based model of dynamic brain function which correlates well with both clinical and pre-clinical experimental data.Consistent at both the anatomical and neurochemical levels, Hobson proposes the secret of consciousness experience to lay in fine interplay of the brain's modular systems of activation, "giving equivalent subdivisions of consciousness in accordance with the activity of [the various] anatomical and physiological modular specialisations of different brain regions". In this model, the modularity is to be based upon purely anatomical distinctions; the physiological affect according to the dynamic modulatory effects of the various neurotransmitter environment in which the nervous tissues are bathed from one instant to another. The explicit hypothesis here, states that "the brain creates the unity of conscious experience via the synchronisation of its elements". So,.... what are the elements ? It has for a long time been known that the activity of neural circuitries in the brainstem' reticular formation and projecting thalamocortical pathways are involved in the maintenance and variation in reports of conscious experience. A variety of brain activity recording techniques (from EEG to fMRI) have continued to implicate these same regions over time, but, combined with the increasingly detailed resolution of the modern brain scanning machines, the advent of a refined molecular biology and functional psychopharmacology has shed much light upon the dynamics of the component brain circuits involved. For example, we now believe that the aminergic neurotransmitter seratonin (ana 5-HT, an important chemical modulator thought to be involved in sensory perception and memory formation) is not released during normal periods of sleep (a typically ‘unconscious' time for most of us). Does its absence therefore explain the lack of memory for dream imagery ? Hobson suspects that it does, argues his case well, and proposes the neural origin of consciousness to lay firmly within the thalamocortical projection systems of the forebrain structures. His ‘binding' makes no dependence upon the 40 Hz-type of synchrony theory, nor is he reductive enough to evoke the contribution of microtubule quantum effects. His explanation remains firmly within the realms of testable hypotheses involving the conscious phenomenology of both normal and clinical human presentations. The take-home model of Hobson is the AIM model of conscious states, the name an acronym combining the features he proposes to be most important in accounting for the variation(s) of experience reported. A very welcome 3-D, dynamic model (in contrast to the more frequently linear models of the past) accompanied by clear visual illustrations, we are taken through the model with clarity and consistent reference to relevant clinical findings in a way accessible to the informed reader. This is not a book which falls at the last hurdle, a final chapter lacking in solution, leaving the reader feeling let down. In brief, the proposal affords that one's subjective conscious experience be accountable according to the combined AIM three-component vector space ("conscious state space") comprising one's Activation state (high-low), Information source (sensory external-internal) and Mode of processing (cholinergic-aminergic neurochemical modulation). The reasoning is coherent and the neuroscience data accurate to date, with references and further reading offered for those wishing to gain more from the physiological research literature. I will be certainly be adding this volume to my tutorial teaching list. I like the way Hobson writes. I like his clarity, modesty and his perseverence with a difficult subject (he does not claim to have ‘explained' consciousness). For me, his work does nonetheless help to explain at least something of the mind-brain unity baggage itself that is so often forgotten about: no brain,...no consciousness, ..(as far as I know). The mechanisms by which my own specific brain functions correlate/cause/effect my conscious experience, continue to derive explanatory value (if not a fuller understanding) from the type of model recurrent in Hobson's work. This latest, is no exception.

I undervalued this book when I first read it, although even then I underlined passages as I went. At the time of my first reading, I did not wish to believe that the mind-body problem might be resolved by brain scientists in the very near future. But now, after rereading sections of the book years later, I realize the facts do indeed point in that direction. As Hobson details in this book, states of consciousness (waking, sleep, dreaming) are controlled by brain chemistry. The research which underlies this assertion is well supported, and its implications are of the greatest importance. If our very sense of self is subject to alteration by changes in our brain chemistry, as is so obviously the case during sleep and dreaming, then there can no longer be a question that we are indeed material beings, even at the level of consciousness. For this highly significant fact alone, I personally think this book deserves far wider recognition than it has apparently received. Dr. Hobson, a world-renowned sleep and dreaming scientist, is ideally qualified to deliver this message, whether we wish to pay the appropriate attention to him or not.

This book is rather naive and overoptimimistic with respect to the state of consciousness research today. It's not that bad of a book for its point of view, but given the title a more balanced approach would be more appropriate. To create this balance, read this book together with Horgan's book on consciousness, or if you want something even more penetrating, read any of McGinn's books on the subject.