New perspectives for the study of lucid dreaming: From brain stimulation to philosophical theories of self-consciousness

Dreaming is often described as a state of cognitive deficiency characterized by a loss of self-reflection, orientational instability regarding persons, times, and places, deficient shortand long-term memory, and a lack of control over volition and attention (Hobson, Pace-Schott & Stickgold, 2000). On the neurophysiological level of description, a plausible correlate of such cognitive deficiencies is the hypoactivation of the prefrontal areas during rapid eye movement (REM) sleep, which is the sleep stage in which the most vivid dreams occur (Hobson et al., 2000). Specifically, neuroimaging studies using positron emission tomography (PET) have shown that the dorsolateral prefrontal cortex (DLPFC), which is associated with executive abilities such as expectancy and working memory in wakefulness (Fuster, 2008), is selectively deactivated during REM sleep (Muzur, Pace-Schott, & Hobson, 2002; Maquet et al., 2005). This finding seems to fit in well with the common loss of self-reflective awareness and rational thought in dreams (Kahn, 2007). Nevertheless, even though early studies tended to emphasize the absence of cognition in the dream state (e.g., Rechtschaffen, 1978), it appears that the actual prevalence and quality of cognitive activity varies considerably in dreams (Meier, 1993; Kahn & Hobson, 2005). The most prominent example of wakelike cognition in nocturnal dreams is dream lucidity, which is characterized by heightened levels of cognitive clarity as well as by metacognitive insight into the hallucinatory nature of the dream state. New perspectives for the study of lucid dreaming: From brain stimulation to philosophical theories of self-consciousness