Portal de Periódicos da CAPES

Preface

2010; Elsevier BV; Volume: 5; Issue: 2 Linguagem: Inglês

10.1016/j.jsmc.2010.01.012

1556-4088

J.F. Pagel,

Neuroscience and Music Perception

Dreaming is the longest studied yet least understood of cognitive states. The pedigree of dream study is ancient. The first decipherable human scripts inscribed into Mesopotamian clay 6,000 years ago include records of King Gudea's dreams that were perceived as messages from his gods. For the Ancient Greeks and Egyptians, it was most important to distinguish between “true dreams” (those that could be messages from god) and “false dreams.” Rene Descartes built on this search for truth. He developed his scientific method while attempting to differentiate dreaming from external reality. The scientific study of dreams achieved prominence at the turn of the last century. Freud based his psychoanalytic theories of mental functioning on interpretations of dreams, focusing on the psychopathology associations of bizarre dreams and eventually giving us a definition of dreaming as “wish fulfillment.” In the 1960s, the apparent realization that rapid eye movement (REM) sleep was dreaming broke through 500 years of belief in Cartesian dualism, leading us into a modern age of unitary activation-synthesis theory. If REM sleep is dreaming, philosophers and scientists should require no other evidence to conclude that mind—in neuroscientific actuality—equals brain. In this new millennium, the scientific study of dreams has come full circle. Psychoanalysis, while useful as a cognitive model for the study of film, art, and intrapersonal psychodynamics, has generally failed as a treatment for psychiatric disease. After 50 years of dogma, most scientists and philosophers accept that research overwhelmingly demonstrates that dreaming and REM sleep are doubly dissociable. REM sleep occurs without dreaming and dreaming without REM sleep.1.Solms M. Dreaming and REM sleep are controlled by different brain mechanisms.in: Pace-Schott E. Solms M. Blagtove M. Sleep and dreaming: scientific advances and reconsiderations. Cambridge University Press, Cambridge (UK)2003: 51-58Google Scholar Even the evidence supporting a special relationship between REM sleep and dreaming is equivocal, with only few a methodologically limited studies suggesting that REM sleep dream recall and content differs from the dreams of sleep onset.2.Domhoff G.W. The scientific study of dreams; neural networks, cognitive development and content analysis. American Psychological Association, Washington, DC2003Crossref Google Scholar Most sleep medicine physicians define dreaming as mentation reported as occurring in sleep. However, this definition contradicts the psychoanalytic definition for dream, by restricting dreaming to sleep irrespective of content. This definition also differs from the REM sleep–equals–dreaming model in requiring a dream report. This perspective---that a dream report is required if REM sleep equals dreaming---is not universally accepted. With the advent of micropipette brain slice techniques, knock-out mice, and central nervous system scanning with functional magnetic resonance imaging, squib, and positron emission technology, we now understand far more about the REM sleep state than we understand about dreaming.3.Pace-Schott E.F. Postscript: recent findings on the neurobiology of sleep and dreaming.in: Pace-Schott E.F. Solms M. Blagrove M. et al Sleep and dreaming: scientific advances and reconsiderations. Cambridge University Press, Cambridge2003: 335-350Google Scholar If REM sleep does not equal dreaming, the requirement for a dream report restricts scientific studies of dreaming to subjects capable of cognitive interaction (generally humans). Scientists loath to giving up the role of dreaming as a behavioral aspect of the REM sleep neurocognitive model have stretched the definition of dreaming to include parasomnias and the REM sleep–associated states of narcolepsy, with dreaming defined as any bizarre, hallucinatory mental activity occurring during sleep or while awake.4.Pagel J.F. Blagrove M. Levin R. et al.Defining dreaming—a paradigm for comparing disciplinary specific definitions of dream.Dreaming. 2001; 11: 195-202Crossref Scopus (59) Google Scholar, 5.Pagel JF, Scrima L. Psychoanalysis and narcolepsy. In: Goswami M, Pandi-Perumal, Thorpy M, editors. Narcolepsy. Humana/Springer, in press.Google Scholar Theorists suggest that such mentation indicates the occurrence of REM sleep, whether occurring in polysomnographic REM sleep, in non-REM sleep, or even in waking.6.Neilsen T. A review of mentation in REM and NREM sleep: “covert” REM sleep as a possible reconciliation of two opposing models.in: Pace-Schott E. Solms M. Blagtove M. Sleep and dreaming: scientific advances and reconsiderations. Cambridge University Press, Cambridge (UK)2003: 59-74Google Scholar The other sleep mentation is classified as non-REM sleep or sleep “mental activity” (See the article by Lawrence Scrima elsewhere in this issue for further exploration of this topic.). This approach preserves the REM sleep–equals–dreaming correlate, but requires a redefinition of both sleep states and dreaming.7.Pagel J.F. The limits of dream—a scientific exploration of the mind/brain interface. Academic Press (Elsevier), Oxford (UK)2008Google Scholar Based on this perspective, the most commonly reported dreams, continuity dreams reflecting the experience of waking life, are not dreams. Perhaps this is dreams' darkest hour. The percentage of scientific articles addressing dreaming peaked with the discovery of REMS but has now declined to the lowest level in 60 years (see the graph). What we know today about dreaming is far less than what we thought we knew a generation ago. Much older work is methodologically limited by lack of definition, small sample size, and constraints of theoretical perspective. Even among this issue's small sample of dream scientists, definitions of dreaming vary so that different authors are writing about mutually exclusive topics—all called dreaming. It remains unclear, as well, as to what part, if any, of the highly developed REM sleep neurocognitive model applies to cognitive state of dreaming. This issue provides a purview of the current approaches being used by major researchers involved in the scientific and clinical study of dreaming. Milton Kramer reviews the status of scientific rigor in dream research. Mark Schredl reviews our current understanding of variables affecting dream recall. Bill Domhoff reviews our current understanding of dream content, highlighting the lack of evidence that REM sleep dreaming differs in content from the dreaming associated with other sleep stages. Carlyle Smith addresses the association of REM sleep with learning and memory and the proposed role for dreaming in this process. My own article is an evidence-based review of the neurochemistry affecting dreaming and nightmares, indicating that the medications affecting dreaming differ from those affecting REM sleep. For those readers interested in maintaining their belief in dreaming as a REM sleep epiphenomenon, Lawrence Scrima suggests that narcolepsy may be an the ideal model for the study of dreaming. This issue's clinical focus is reflected in its emphasis on the theory, diagnosis, and treatment of the most common of the parasomnias—nightmares. Ernest Hartmann highlights the contextual imagery involved in such powerful dreams. Mylène Duval and Antonio Zadra address our current understanding of nightmares, and Ross Levin addresses the apparent functions for nightmares in emotional processing. Barry Krakow and Antonio Zadra focus on treatment of the nightmares associated with posttraumatic stress disorder, while Alan Seigel addresses the current use of dream reports in clinical psychotherapy. Many other and larger publications about dreams focus on phenomenology and theory. This issue differs from those in its emphasis on scientific evidence, providing for the reader the best available review of the current status of dream science, as well as a review and assessment of clinical approaches to dreaming and nightmares. However, this issue has a prominent subtext that can be read in both its brevity and lack of positive conclusions: What we scientifically understand about both dreams and nightmares is profoundly limited. After 6000 years of study, this cognitive state remains both an enigma and an opening for the enterprising open-minded scientist fascinated by the unknown.