The Dreaming Brain/Mind: a Role in Understanding Complex Mental Disorders?
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by AIR Universita degli studi di Milano OPINION ARTICLE published: 31 January 2012 PSYCHIATRY doi: 10.3389/fpsyt.2012.00003 The dreaming brain/mind: a role in understanding complex mental disorders? Armando D’Agostino1,2*, Ivan Limosani 2 and Silvio Scarone1,2 1 Department of Medicine, Surgery and Dentistry, Università degli Studi di Milano, Milan, Italy 2 Department of Mental Health, San Paolo Hospital, Milan, Italy *Correspondence: [email protected] Abnormalities in the sleep/wake cycle and few contemporary researchers to bind these enology, bursts of “covert” REM sleep have within sleep itself have extensively been complex phenomena, with electrophysi- been hypothesized to underlie mental studied in a broad range of psychiatric ological, neurochemical, and cerebrofunc- activity during other stages. This observa- and neurodegenerative disorders. Despite tional data now pointing to shared patterns tion is based on the correlation between increasing evidence for a mechanistic across dreaming and psychotic experiences hallucinatory subjective experiences and overlap between the disruptions of circa- (Hobson, 2004; Gottesmann, 2006). EEG configurations containing elements dian timing control and neuropathology, One relevant issue in the scientific study of both REM and NREM. Moreover, the the relationship remains unclear (Wulff of dreams is bound to the limits of our cur- most vivid NREM mentation reports have et al., 2010). One possible way to address rent understanding of cerebral activation been collected when transient EMG sup- this problem from a psychiatric perspec- patterns across different stages of sleep. pressions and phasic muscle twitches, which tive is to compare the phenomenological Despite early observations binding dreams are typical of REM sleep, were recorded dur- correlate of sleep with the waking menta- to REM sleep physiology, it is now widely ing sleep onset (Nielsen, 2000). tion observed in patients. Indeed, so-called accepted that dreams occur across all stages Prefrontal hypometabolism and limbic/ “positive” symptoms such as abnormal (Nir and Tononi, 2010). However, mental paralimbic hypermetabolism have been senso-perceptual experiences or thought activity across sleep does differ, ranging reported in both waking schizophrenic processes ranging from ideas of reference to from simple thought-like experiences to and manic psychotic subjects (Molina et al., highly structured delusions, share substan- full-blown hallucinoid dreams, which 2005; Minzenberg et al., 2009; Brooks III tial similarities with dream phenomenol- have been shown to be underpinned by et al., 2010). On the neurochemical level, ogy. The same process by which psychotic NREM and REM polysomnographic pat- positive symptoms have been hypoth- patients progress from salience attributed to terns respectively (McNamara et al., 2010). esized to result from abnormal regulation irrelevant stimuli to a new, highly relevant Although a direct correlation between of NMDA-dependent synaptic plasticity meaning, appears to occur in dreams, where dreaming and underlying neurofunctional by transmitters like dopamine, acetylcho- a single hallucinatory image can convey “an modifications remains a challenge for line and serotonin (Stephan et al., 2009). immediate emotionally compelling mean- sleep/dream researchers, some studies have Long-term potentiation (LTP), a key ing that is not related to the image in any shown a relative hyperactivation of cerebral mechanism of synaptic consolidation, is obvious way” (Feinberg, 2011). With the regions related to emotional and affective similarly thought to rely on glutamatergic exception of the rare experience of lucid- life (i.e., amygdala and anterior cingulate transmission, with sleep spindles having ity, the dreamer has no recognition of cortex) and a relative hypoactivation of the been recognized as a possible neurophysio- his objective status, i.e., being asleep and frontal cortex, mainly in its dorsolateral logical correlate of the consolidation dialog vastly detached from the external environ- prefrontal regions, during REM sleep (Nir between the hippocampus and neocorti- ment; dream images produced uniquely by and Tononi, 2010). This functional condi- cal structures during sleep (Diekelmann endogenous neural activity are interpreted tion of the brain is mediated by a complex and Born, 2010; Fogel and Smith, 2011). as coming from the external world; height- and interactive neurochemical pathway In this regard, it seems interesting to note ened and often incongruous emotions are within which a strong increase of cholin- that sleep spindle density has been found coupled with a decrease in ego functions ergic activity is coupled with the reduction to be reduced in schizophrenic subjects which ultimately leads to instinctual behav- of serotonergic and noradrenergic firing (Ferrarelli et al., 2007). Indeed, procedural iors and severe impairment in reality test- rates. Mesolimbic dopaminergic activa- and declarative memory consolidation ing (Hobson, 2009). The striking similarity tion has also been hypothesized to occur impairment has been correlated to sleep between these aspects of dreaming and psy- in dream sleep in absence of serotonergic disturbances in these patients (Manoach chosis has been observed by most of the inhibition (Gottesmann, 2002). Indeed, a et al., 2010; Seeck-Hirschner et al., 2010). funding pioneers of the modern approach raise in cortical dopamine activity has been The mixed findings that have historically to psychopathology. Indeed, it is largely causally linked to the generation of night- emerged from sleep studies in this popu- unknown that Emil Kraepelin extensively mares, possibly implying an intensification lation could at least in part be attributed studied his own dreams with the aim of pro- of cholinergically driven characteristics of to the complex nosographical boundaries gressing his understanding of schizophrenic REM sleep-related dream mentation. In of the disorder. In our view, abnormalities thought disorder (Engels et al., 2003). order to account for the relevant findings in sleep-dependent consolidation mecha- Recent advances in neuroscience have led which link REM sleep to dream phenom- nisms should be considered in relationship www.frontiersin.org January 2012 | Volume 3 | Article 3 | 1 D’Agostino et al. Dream sleep and psychosis to positive symptoms rather than to the activity in posterior brain structures” (Voss environmentally predisposed subjects. broader concept of schizophrenia, and one et al., 2009). In other words, reactivation of Similarities and differences in brain func- recent study seems to suggest that neuro- frontal lobes within REM sleep appears to tion will have to be addressed directly in the cognitive deficits do correlate with sleep underlie awareness within the hallucinatory future by binding sleep and dream research spindle density in a population of psychotic nature of one’s experience. Although the with research in psychotic disorders within patients belonging to several different diag- multidimensional construct of insight has the same experimental framework. nostic categories (Keshavan et al., 2011). been shown to reflect a vast and complex Sleep-dependent processing of memory neural circuitry in psychotic patients, fron- REFERENCES may be viewed as a continuous adaptation tal lobe processing is thought to play a criti- Antonius, D., Prudent, V., Rebani, Y., D’Angelo, D., of the brain to the external environment, of cal role (Antonius et al., 2011). Disruption Ardekani, B. A., Malaspina, D., and Hoptman, M. J. which dreaming constitutes the subjective of synaptic plasticity in the prefrontal cor- (2011). White matter integrity and lack of insight in schizophrenia and schizoaffective disorder. Schizophr. epiphenomenon. 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