Psychological Bulletin Copyright 2005 by the American Psychological Association 2005, Vol. 131, No. 1, 98–127 0033-2909/05/$12.00 DOI: 10.1037/0033-2909.131.1.98 Psychobiology of Altered States of Consciousness Dieter Vaitl Niels Birbaumer University of Giessen University of Tu¨bingen and University of Trento John Gruzelier and Graham A. Jamieson Boris Kotchoubey and Andrea Ku¨bler Imperial College London University of Tu¨bingen Dietrich Lehmann Wolfgang H. R. Miltner University Hospital of Psychiatry University of Jena Ulrich Ott Peter Pu¨tz University of Giessen Institute for Frontier Areas of Psychology and Mental Health Gebhard Sammer Inge Strauch University of Giessen University of Zurich Ute Strehl Jiri Wackermann University of Tu¨bingen Institute for Frontier Areas of Psychology and Mental Health Thomas Weiss University of Jena The article reviews the current knowledge regarding altered states of consciousness (ASC) (a) occurring spontaneously, (b) evoked by physical and physiological stimulation, (c) induced by psychological means, and (d) caused by diseases. The emphasis is laid on psychological and neurobiological ap- proaches. The phenomenological analysis of the multiple ASC resulted in 4 dimensions by which they can be characterized: activation, awareness span, self-awareness, and sensory dynamics. The neurophys- iological approach revealed that the different states of consciousness are mainly brought about by a compromised brain structure, transient changes in brain dynamics (disconnectivity), and neurochemical and metabolic processes. Besides these severe alterations, environmental stimuli, mental practices, and techniques of self-control can also temporarily alter brain functioning and conscious experience. Consciousness has come under renewed scientific investigation, methods of cognitive neuroscience (for a review, see Gazzaniga, with respect to both the various levels of consciousness and the 2000; Mesulam, 2000; Zeman, 2001). Everyday conscious aware- content of consciousness, through advances in the models and ness is but the tip of an iceberg, underneath which there is a realm Dieter Vaitl, Center for Psychobiology and Behavioral Medicine and chophysics, Institute for Frontier Areas of Psychology and Mental Health, Department of Psychology, University of Giessen, Giessen, Germany; Freiburg, Germany; Inge Strauch, Department of Clinical Psychology, Niels Birbaumer, Institute of Medical Psychology and Behavioral Neuro- University of Zurich, Zurich, Switzerland. biology, University of Tu¨bingen, Tu¨bingen, Germany, and Center for This work was supported by the Institute for Frontier Areas of Psychol- Cognitive Neuroscience, University of Trento, Trento, Italy; John Gruze- ogy and Mental Health, Freiburg, Germany. The Altered States of Con- lier and Graham A. Jamieson, Department of Neuroscience and Psycho- sciousness (ASC) Consortium, founded in 1998, was devoted to the neu- logical Medicine, Imperial College London, London, United Kingdom; rophysiological, psychological, and behavioral components of altered Boris Kotchoubey, Andrea Ku¨bler, and Ute Strehl, Institute of Medical states of consciousness. Several psychophysiological laboratories partici- Psychology and Behavioral Neurobiology, University of Tu¨bingen; Di- pated in this endeavor and exchanged their results, ideas, and concepts at etrich Lehmann, The KEY Institute for Brain–Mind Research, University four consecutive special symposia held in Sils-Maria, Switzerland, from Hospital of Psychiatry, Zurich, Switzerland; Wolfgang H. R. Miltner and 1999 to 2002. Thomas Weiss, Department of Biological and Clinical Psychology, Uni- Correspondence concerning this article should be addressed to Dieter versity of Jena, Jena, Germany; Ulrich Ott and Gebhard Sammer, Center Vaitl, Clinical and Physiological Psychology, Department of Psychology, for Psychobiology and Behavioral Medicine, University of Giessen; Peter University of Giessen, Otto-Behaghel-Str 10, D-35394, Giessen, Germany. Pu¨tz and Jiri Wackermann, Department of Empirical and Analytical Psy- E-mail: [email protected] 98 PSYCHOBIOLOGY OF ALTERED STATES OF CONSCIOUSNESS 99 of relatively uncharted processes, which are likely to be just as application to ASC of newly developed methods and techniques in complex as those of so-called altered states of consciousness cognitive neuroscience, including multichannel electroencepha- (ASC), which have tended to defy systematic elucidation; the brain lography (EEG) and magnetoencephalography (MEG), neuroelec- is functionally in a constant state of flux and alteration. There are tric and neuromagnetic source imaging, positron emission tomog- now attempts to systematically explore, conceptualize, and place raphy (PET), and functional magnetic resonance imaging (fMRI), these phenomena within the context of neuroscience, which is the provide new insights into altered brain functioning.1 subject of this review. We examine advances in understanding the Apart from focusing on such findings, this review also includes more extreme phenomena traditionally included under the rubric models of neuroscientific approaches to various ASC. The eviden- of ASC (Ludwig, 1966) that have accumulated about their neuro- tial base is mainly devoted to a multilevel approach, including physiological, cognitive, and biological underpinnings, together biological, behavioral, cognitive, and subjective domains, with the with interrelations between the various domains, including phe- focus being largely on studies including more than one domain. As nomenological analysis. As will be seen, so far the evidence is shown in Table 1, altered states can be classified by their origin, largely empirical in nature, and there is no overarching model for that is, spontaneous, induced, or pathological. In the table some ASC. However, strategies toward this end are proposed in the irreversible pathological conditions have been included, although Discussion section. some authors restrict the term ASC to reversible, short-term con- ASC as part of the general experiential and behavioral repertoire ditions only (Farthing, 1992). The multitude and heterogeneity of have a long history, and ASC were widely accepted earlier when states induced by pharmacological agents was not included here. ideas were being explored of consciousness expansion, meditation, These states are not considered to be unimportant—to the contrary; LSD, and mystical practices. Myriads of topics were considered however, the members of the ASC Consortium focused their but were widely scattered and poorly defined. Several attempts research mainly on clinical conditions or physiological and psy- were made to group the seemingly divergent phenomena and to chological induction methods, which represent a broad field to be organize their multiplicity. For example, in reviewing the literature reviewed all by themselves (for recent reviews of pharmacological- on the hypnagogic state, Schacter (1976) showed that the psycho- induced ASC and affected neurotransmitter systems, see Aghaja- logical and physiological features characterizing the drowsy inter- nian & Marek, 1999; Parrott, 2001; Snyder, 1996; Vollenweider & val between waking and sleeping could be elucidated in a descrip- Geyer, 2001). The classification provided in Table 1 has been used tive sense. This appeared then to be the only way of synthesizing to structure our review. divergent approaches, given the fact that there were no standard experimental procedures and comprehensive theoretical concepts Spontaneously Occurring ASC for the diverse phenomena of ASC that developed and continue to develop in relative isolation. This was exemplified by the anthro- During daily activities, spontaneous fluctuations in wakefulness, pological cross-cultural studies of Bourguignon (1966, 1973), alertness, and vigilance occur. They are subjectively experienced which showed that in most cultures there were forms of institu- as being part of phenomenal awareness, which oscillates on the tionalized ASC that seemed to emerge from common, basic psy- wakefulness–drowsiness–sleep onset continuum. Four major chobiological capacities. classes of spontaneously occurring ASC are addressed here: states The anthropological studies have revealed the ubiquity of and of drowsiness, daydreaming, hypnagogic states, and sleep and the similarity between phenomena. Recently, a number of theories dreaming. Among the spontaneously occurring ASC, near-death have argued for common psycho- and neurophysiological pro- experiences are an infrequent and peculiar class of phenomena, cesses underlying different ASC such as meditation, trance, and detailed later in this section. shamanism. Mandell (1980), for instance, postulated hypersyn- chronous hippocampal–septal (ictal or interictal) activity occurring States of Drowsiness during microseizures to be the biological bases for ecstatic and mystical states. In the same vein, Persinger (1983) claimed that Variations of vigilance within the normal sleep–wake cycle mystical experiences are associated with transient microseizures in usually do not induce ASC. Alterations of consciousness may the temporal lobe in nonepileptic individuals. However, it is ques- tionable whether such transient paroxysmal processes can account 1 Only EEG and MEG allow for the time resolution to observe online for the multiplicity and diversity of ASC. In contrast, the present changes of mental processes, both reflecting summation of synchronized review aims at a broader approach by shedding