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Understanding Consciousness: Implications and Consequences (review)
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Perspectives in Biology and Medicine 46.2 (2003) 297-304

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Understanding Consciousness
Implications And Consequences

Mark W. Mahowald


J. Allan Hobson. The Dream Drugstore: Chemically Altered States of Consciousness. Cambridge: MIT Press, 2001. Pp. 333. $27.95; Gerald M. Edelman and GiulioTononi. A Universe of Consciousness. How Matter Becomes Imagination. New York: Basic Books, 2000. Pp. 274. $17.

THE CONCEPT OF CONSCIOUSNESS has fascinated philosophers and scientists for centuries, and remains one of the frontiers of science. The Cartesian notion of consciousness as separate from the brain is no longer tenable: recent advances in neuroscience have clearly established consciousness as a function of the entire brain, likely different areas at different points in time. This concept of "whole brain" involvement in consciousness will serve to explain many different, and occasionally pathological, human experiences and behaviors.

These two fascinating books add most important pieces to the puzzle of consciousness, and permit speculation regarding implications of consciousness [End Page 297] for the human condition. The Dream Drugstore is the culmination of Allan Hobson's professional career, which has been dedicated to understanding the relationship of sleep and dreaming. He has expanded and refined the AIM (activation, input, and modulation) concept, which undoubtedly explains many previously enigmatic (and formerly felt to be unrelated) human experiences and behaviors. This concept creates a three-dimensional "mind space" defined by three variables: activation, the level of brain activation; input, the information made available to the brain (external-exogenous vs. internal-endogenous); and modulation, the degree of neurochemical bias (aminergic vs. cholinergic).

As humans, we spend our time in one of three different states of being: wakefulness, rapid-eye movement (REM) sleep, or non-rapid-eye movement (NREM) sleep. Each of these states is accompanied by a wide variety of physiological variables, which usually occur in concert to form a fully declared state. According to Hobson, the primary variables are AIM (Figure 1). Although it was formerly thought that the three primary states of being were "all-or-none" and mutually exclusive, both animal experiments and human [End Page 298] studies show that admixture of state-determining variables is common and may result in impressive clinical symptoms. For instance, cataplexy, the sudden loss of muscle tone triggered by emotionally laden events in patients with narcolepsy, represents the intrusion of one element of REM sleep (somatic muscle paralysis) into wakefulness, resulting in the striking clinical syndrome of generalized muscle weakness triggered by emotion (laughter, anger, surprise, etc.) in a fully alert person. Another example is REM sleep behavior disorder (RBD), a condition in which patients "act out their dreams" (or "dream out their acts"), often with violent or injurious results. RBD represents the parent state of REM sleep minus one of its important and usually defining elements—somatic muscle paralysis (or, conversely, REM sleep plus one element of wakefulness—preservation of muscle tone). Other examples commonly experienced by perfectly normal people, particularly in the setting of sleep deprivation, are sleep paralysis (awakening to find one's whole body paralyzed) and hypnagogic hallucinations (vivid hallucination-like dreams occurring just before sleep onset).

Cataplexy, sleep paralysis, hypnagogic hallucinations, and RBD are well-recognized clinical phenomena representing admixture of state-determining variables. Hobson has taken the state admixture concept to a higher and more complex level, proposing that virtually any area of AIM-defined brain space may be traversed or occupied under certain circumstances, resulting in an infinite number of possible combinations of clinical experiences or symptoms. His book deals primarily with the normal brain space occupied by conventional dreams occurring in sleeping brains, and those portions of brain space occupied by waking brains altered by endogenous primary mental disorders (schizophrenia or psychogenic dissociative disorders) or by exogenous drugs (recreational or prescription). The differences between dreams and either drug-induced or mental illness-related experiences of the brain depend upon varying levels of the AIM parameters. Functional neuroimaging studies support alteration in brain function in dreaming and in some psychiatric conditions that likely are a manifestation of varying AIM parameters (Andreasen et al. 1994).

The concluding chapter of The Dream...