The neural correlates of dreaming

Abstract

2Consciousness never fades during wake. However, if awakened from sleep, sometimes we report dreams and sometimes no experiences. Traditionally, dreaming has been identified with REM sleep, characterized by a wake-like, globally 'activated', high-frequency EEG. However, dreaming also occurs in NREM sleep, characterized by prominent low-frequency activity. This challenges our understanding of the neural correlates of conscious experiences in sleep. Using high-density EEG, we contrasted the presence and absence of dreaming within NREM and REM sleep. In both NREM and REM sleep, the presence of dreaming was associated with a local decrease in low-frequency activity in posterior cortical regions. High-frequency activity within these regions correlated with specific dream contents. Monitoring this posterior 'hot zone' predicted the presence/absence of dreaming during NREM sleep in real time, suggesting that it may constitute a core correlate of conscious experiences in sleep.All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/012443 doi: bioRxiv preprint first posted online Dec. 30, 2014; 3 An ongoing stream of experiences accompanies every waking moment. Sleep is the only time in which consciousness fades under normal physiological conditions: subjects awakened from sleep, especially early in the night, report that they were not experiencing anything up to 30% of the time 1 . At other times, subjects awakened from sleep report dreams -a stream of vivid experiences that occur despite being immobile, unresponsive, and largely disconnected from the environment. Thus, unlike wakefulness, sleep can be associated with either the presence or absence of conscious experiences. In addition, experiences in dreams can assume many forms, ranging from pure perceptual experiences to pure thought, from simple images to temporally unfolding narratives, which are often similar to awake conscious states but at times can be different in interesting ways 2,3 .The discovery of rapid eye movement (REM) sleep -the 'third state of being' besides wake and non-REM (NREM) sleep -led initially to a straightforward view of the neural correlates of dreaming 4 : the wake-like, high-frequency, 'activated' EEG 5,6 of REM sleep was thought to be associated with the presence of dream experiences, and the lowfrequency activity of NREM sleep with the absence of dreaming. However, later studies showed that up to 70% of NREM sleep awakenings yield reports of dream experiences 1 .Conversely, in a small but consistent minority of cases, subjects deny having had any experience when awakened from REM sleep. Thus, whether one experiences something or not during sleep cannot be determined simply by assessing one's behavioral state based on traditional EEG features or neuroimaging correlates 7,8 .The paradoxical occurrence of both the presence and absence of experien...

Predicting Dream Recall: EEG Activation During NREM Sleep or Shared Mechanisms with Wakefulness?

“…Interestingly, Siclari et al (2014) found that DR, considered as conscious experience, was related to increased high-frequency power (18-50 Hz) and reduced low-frequency power (1-12 Hz).…”

“…Furthermore, some studies reported a relationship between high frequency range (18-50 Hz, i.e., gamma activity) and DR (Siclari et al 2014;Voss et al 2014). In particular, a recent withinsubjects study revealed that brain activity characterized by higher power in high-frequency range is associated to the presence of recall on awakening both during REM and NREM sleep (Siclari et al 2014). Also it was reported that the stimulation on the fronto-temporal area in the gamma band by transcranial direct current stimulation (tDCS) during REM sleep elicits lucid dreams (Voss et al 2014).…”

“…Therefore, EEG activation could facilitate the consolidation and storage of the mental sleep contents during sleep. Furthermore, some studies reported a relationship between high frequency range (18-50 Hz, i.e., gamma activity) and DR (Siclari et al 2014;Voss et al 2014). In particular, a recent withinsubjects study revealed that brain activity characterized by higher power in high-frequency range is associated to the presence of recall on awakening both during REM and NREM sleep (Siclari et al 2014).…”

“…It is well-known that we cannot have directly access on dream experience, so several works investigated the EEG pattern related to the subsequent dream reports, which are-intrinsically-retrospective (Chellappa et al 2011;Esposito et al 2004;Marzano et al 2011a;Scarpelli et al 2015a;Siclari et al 2014;Takeuchi et al 2003).…”

Sny, świadomość i jaźń: perspektywa filozoficzna

“…też Voss & Hobson 2015 badali, czy stymulacja elektryczna rejonów czołowo-skroniowych mózgu, które zwykle są deaktywowane podczas snu REM, mogą wywołać świadomość śnienia, czyli świadomość tego, że się śni. Wreszcie, kontrast między śnieniem a jego brakiem podczas tej samej fazy snu może poszerzyć istniejące badania nad neuronowymi korelatami świadomości (Noreika 2009, Siclari 2014.…”