Dreaming: A psychiatric view and insights from the study of parasomnias

This paper provides a psychiatric view of the psychological, experimental, and medical literature on dreams, along with insights gained from the study of parasomnias. The psychoanalytic theory of dreams developed by Freud considers dreams to be highly meaningful mental products, with unconscious processes playing a major role. However, it has been quite difficult to devise operational criteria to rigorously test this theory. With the discovery of REM sleep and the NREM/REM sleep cycle, sleep laboratory techniques facilitated the systematic sampling of dreams. Studies carried out to examine dreams focused on their individual context were hampered by small sample sizes. Studies of dreams from larger samples of subjects involved in a particular and often disturbing life circumstance posed various challenges in interpretation. Experimental manipulations of REM sleep and associated dreaming have been carried out, with various theoretical and methodological short-comings. REM sleep deprivation studies have suggested that REM sleep, and associated dreaming, may perform vital functions. Studies on the childhood development of dreaming are also pertinent. The neurobiology of REM sleep as the primary source of data from which to make inferences on dreaming was pioneered by Hobson and McCarley in their "activation-synthesis" model (recently updated as the activation/input/modulation-AIM-model by Hobson), in which brainstem activation during REM sleep randomly stimulates the forebrain, which then attempts to "synthesize" the information into coherent dreams. In this model, dreams are not intrinsically meaningful, though some meaning may accrue through the forebrain's efforts to "make sense" of its physiologically determined stimulation. Various problems with the activation-synthesis model have been identified. A recent critique by B. E. Jones discusses how brainstem activation of the forebrain can originate from highly ordered brainstem circuits that generate not only specific motor patterns but also complex organized behaviors. The possible relation to dreaming of the "hippocampal theta rhythm" in REM sleep is discussed. The "neuropsychology of dreaming" proposed by Solms is presented, based on the large study of neurological patients with widely distributed brain lesions. Neuroimaging techniques and their application to dreaming across the sleep-wake cycle are another new source of data. The second part of this article discusses abnormal dreaming with the parasomnias, which are the behavioral, autonomic nervous system and experiential disturbances that can accompany sleep. REM sleep behavior disorder is the prototypic dream-enacting parasomnia in which the characteristic generalized muscle paralysis of REM sleep, i.e. "REM atonia", becomes compromised, allowing for behavioral release associated with stereotypically altered dreams involving the dreamer being threatened or attacked by unfamiliar people or animals. Sleepwalking and sleep terrors in adults, obstructive sleep apnea (OSA "pseudo-RBD"), nocturnal seizures and nocturnal dissociative disorders can also present with dream-enacting behaviors. The recently identified "epic dream disorder" features relentless, neutral-content "epic" dreaming without emotionality that is experienced to occur throughout sleep.