Trips for everyone

Abstract

The Dream Drugstore: Chemically Altered States of Consciousnessby J. Allan Hobson, MIT Press, 2001. £19.50 (xv + 333 pages) ISBN 0 262 082 934In his latest book, Hobson pursues his grand project of re-conceptualizing psychology by offering a new theory of the ‘brain–mind’. The central theme of the book is that manifestations observed in various states of altered consciousness have some similarities and might be attributed to a common mechanism, namely an alteration of the balance between aminergic (essentially serotonergic and adrenergic) and cholinergic neuromodulation. This aminergic/cholinergic (a/c) balance represents the third axis of the Activation–Input–Modulation (AIM) model, a 3-D state space which is an attempt adequately describe all states of consciousness. In the AIM model, the first dimension describes the general activation of the central nervous system. It measures the rate at which the brain–mind processes information and can be estimated by the EEG power density in the high frequency range. The second axis reflects the source of cerebral input, that is, the extent to which the brain–mind is processing external input. The waking brain tends to be influenced by external stimuli during sleep, it is driven by internally generated signals.The AIM model was originally designed to distinguish wakefulness from REM and non REM sleep. It elegantly explains the sleep/waking and the REM/non REM sleep cycles and has led to exciting hypotheses on the cerebral bases of dreaming activity. However, Hobson wants to go beyond normal sleep/waking phenomena. He poses that many other states of altered consciousness are also accounted for by the model, and especially by an alteration in the a/c modulatory equilibrium: the hypnotic trance, the schizophrenic, hypnagogic and hypnapompic hallucinations, the good and bad trips induced by recreational drugs (LSD, opioids, mescaline, MDMA…)… At some point, the reader realizes that the AIM model is far too restrictive to embrace the specific features of all these conditions. Indeed, a higher dimensional state space would be necessary to account for many aspects of these states. For instance, some important neuromodulatory systems are conspicuously absent from the model (e.g. the dopaminergic and histaminergic systems) although the model include them indirectly through the complex interactions between the various neuromodulatory systems. Likewise, the AIM model awkwardly deals with the action of a single drug on different neuromodulatory systems. Finally, some state-specific features are not explained by AIM model. For instance, what differentiates lucid dreaming from normal dreams is probably neither the global brain activation, nor the source of inputs nor the neuromodulatory context.Nevertheless, the critical element in this book is the Hobson's approach in itself. It is important to have recognized these mental states as scientifically approachable objects and to try to group and categorize them on objective criteria. In this respect, the book provides a pleasurable attempt toward a unitary view on all these states of altered consciousness. The importance of this strategy is illustrated by the number of daring, but readily testable, hypotheses that permeate throughout the book.There is no doubt that this book, as the others by Hobson, will leave a persistent influence on the ways we think about the levels and contents of consciousness. This volume should be recommended to a wide range of readers, not only professionals as psychiatrists, neurologists, psychologists, neuroscientists, or neurophilosophers, but any individual interested in brain–mind function.