Consciousness never fades during waking. However, when awakened from sleep, we sometimes recall dreams and sometimes recall no experiences. Traditionally, dreaming has been identified with rapid eye-movement (REM) sleep, characterized by wake-like, globally 'activated', high-frequency electroencephalographic activity. However, dreaming also occurs in non-REM (NREM) sleep, characterized by prominent low-frequency activity. This challenges our understanding of the neural correlates of conscious experiences in sleep. Using high-density electroencephalography, we contrasted the presence and absence of dreaming in NREM and REM sleep. In both NREM and REM sleep, reports of dream experience were associated with local decreases in low-frequency activity in posterior cortical regions. High-frequency activity in these regions correlated with specific dream contents. Monitoring this posterior 'hot zone' in real time predicted whether an individual reported dreaming or the absence of dream experiences during NREM sleep, suggesting that it may constitute a core correlate of conscious experiences in sleep.
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Stickgold, R., Malia, A., Fosse, R., Propper, R. & Hobson, J.A. Brain-mind states: I. Longitudinal field study of sleep/wake factors influencing mentation report length. Sleep 24, 171–179 (2001).
Nir, Y. & Tononi, G. Dreaming and the brain: from phenomenology to neurophysiology. Trends Cogn. Sci. 14, 88–100 (2010).
Schwartz, S. & Maquet, P. Sleep imaging and the neuro-psychological assessment of dreams. Trends Cogn. Sci. 6, 23–30 (2002).
Aserinsky, E. & Kleitman, N. Regularly occurring periods of eye motility, and concomitant phenomena, during sleep. Science 118, 273–274 (1953).
Moruzzi, G. & Magoun, H.W. Brain stem reticular formation and activation of the EEG. Electroencephalogr. Clin. Neurophysiol. 1, 455–473 (1949).
Steriade, M., Timofeev, I. & Grenier, F. Natural waking and sleep states: a view from inside neocortical neurons. J. Neurophysiol. 85, 1969–1985 (2001).
Maquet, P. Functional neuroimaging of normal human sleep by positron emission tomography. J. Sleep Res. 9, 207–231 (2000).
Chow, H.M. et al. Rhythmic alternating patterns of brain activity distinguish rapid eye movement sleep from other states of consciousness. Proc. Natl. Acad. Sci. USA 110, 10300–10305 (2013).
Siclari, F., Larocque, J.J., Postle, B.R. & Tononi, G. Assessing sleep consciousness within subjects using a serial awakening paradigm. Front. Psychol. 4, 542 (2013).
Foulkes, W.D. Dream reports from different stages of sleep. J. Abnorm. Soc. Psychol. 65, 14–25 (1962).
Nir, Y. et al. Regional slow waves and spindles in human sleep. Neuron 70, 153–169 (2011).
Pigorini, A. et al. Bistability breaks-off deterministic responses to intracortical stimulation during non-REM sleep. Neuroimage 112, 105–113 (2015).
Tononi, G. & Massimini, M. Why does consciousness fade in early sleep? Ann. NY Acad. Sci. 1129, 330–334 (2008).
Purdon, P.L. et al. Electroencephalogram signatures of loss and recovery of consciousness from propofol. Proc. Natl. Acad. Sci. USA 110, E1142–E1151 (2013).
Jones, B.E. From waking to sleeping: neuronal and chemical substrates. Trends Pharmacol. Sci. 26, 578–586 (2005).
Steriade, M., Contreras, D., Amzica, F. & Timofeev, I. Synchronization of fast (30-40 Hz) spontaneous oscillations in intrathalamic and thalamocortical networks. J. Neurosci. 16, 2788–2808 (1996).
Le Van Quyen, M. et al. Large-scale microelectrode recordings of high-frequency gamma oscillations in human cortex during sleep. J. Neurosci. 30, 7770–7782 (2010).
Nielsen, T.A. in Handbook of Behavioral State Control (eds. Lydic, R. & Baghdoyan, H.A.,) 101–128 (CRC, 1999).
Nielsen, T.A. A review of mentation in REM and NREM sleep: “covert” REM sleep as a possible reconciliation of two opposing models. Behav. Brain Sci. 23, 851–866, discussion 904–1121 (2000).
Cavallero, C., Cicogna, P., Natale, V., Occhionero, M. & Zito, A. Slow wave sleep dreaming. Sleep 15, 562–566 (1992).
Voss, U., Holzmann, R., Tuin, I. & Hobson, J.A. Lucid dreaming: a state of consciousness with features of both waking and non-lucid dreaming. Sleep 32, 1191–1200 (2009).
Dresler, M. et al. Neural correlates of dream lucidity obtained from contrasting lucid versus non-lucid REM sleep: a combined EEG/fMRI case study. Sleep 35, 1017–1020 (2012).
Koch, C., Massimini, M., Boly, M. & Tononi, G. Neural correlates of consciousness: progress and problems. Nat. Rev. Neurosci. 17, 307–321 (2016).
Balestrini, S. et al. Reply: The dorsal cingulate cortex as a critical gateway in the network supporting conscious awareness. Brain 139, e24 (2016).
Herbet, G. et al. Disrupting posterior cingulate connectivity disconnects consciousness from the external environment. Neuropsychologia 56, 239–244 (2014).
Revonsuo, A. The reinterpretation of dreams: an evolutionary hypothesis of the function of dreaming. Behav. Brain Sci. 23, 877–901, discussion 904–1121 (2000).
Windt, J.M. Dreaming: a Conceptual Framework for Philosophy of Mind and Empirical Research (MIT Press, 2015).
Christophel, T.B., Hebart, M.N. & Haynes, J.D. Decoding the contents of visual short-term memory from human visual and parietal cortex. J. Neurosci. 32, 12983–12989 (2012).
Postle, B.R. The cognitive neuroscience of visual short-term memory. Curr. Opin. Behav. Sci. 1, 40–46 (2015).
Funk, C.M., Honjoh, S., Rodriguez, A.V., Cirelli, C. & Tononi, G. Local slow waves in superficial layers of primary cortical areas during REM sleep. Curr. Biol. 26, 396–403 (2016).
Schiff, N.D., Nauvel, T. & Victor, J.D. Large-scale brain dynamics in disorders of consciousness. Curr. Opin. Neurobiol. 25, 7–14 (2014).
Sitt, J.D. et al. Large scale screening of neural signatures of consciousness in patients in a vegetative or minimally conscious state. Brain 137, 2258–2270 (2014).
Gökyigĭt, A. & Calişkan, A. Diffuse spike-wave status of 9-year duration without behavioral change or intellectual decline. Epilepsia 36, 210–213 (1995).
Wikler, A. Pharmacologic dissociation of behavior and EEG “sleep patterns” in dogs; morphine, n-allylnormorphine, and atropine. Proc. Soc. Exp. Biol. Med. 79, 261–265 (1952).
Horikawa, T., Tamaki, M., Miyawaki, Y. & Kamitani, Y. Neural decoding of visual imagery during sleep. Science 340, 639–642 (2013).
Malcolm, N. Dreaming and skepticism. Philos. Rev. 65, 14–37 (1956).
Dennet, D.C. Are dreams experiences? Philos. Rev. 85, 151–171 (1976).
Aru, J. et al. Local category-specific gamma band responses in the visual cortex do not reflect conscious perception. J. Neurosci. 32, 14909–14914 (2012).
Murphy, M. et al. Propofol anesthesia and sleep: a high-density EEG study. Sleep 34, 283–291A (2011).
Naro, A., Bramanti, P., Leo, A., Russo, M. & Calabrò, R.S. Transcranial alternating current stimulation in patients with chronic disorder of consciousness: a possible way to cut the diagnostic Gordian knot? Brain Topogr. 29, 623–644 (2016).
Voss, U. et al. Induction of self awareness in dreams through frontal low current stimulation of gamma activity. Nat. Neurosci. 17, 810–812 (2014).
Christoff, K., Gordon, A.M., Smallwood, J., Smith, R. & Schooler, J.W. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proc. Natl. Acad. Sci. USA 106, 8719–8724 (2009).
Perogamvros, L. & Schwartz, S. The roles of the reward system in sleep and dreaming. Neurosci. Biobehav. Rev. 36, 1934–1951 (2012).
Fleming, S.M. & Dolan, R.J. The neural basis of metacognitive ability. Phil. Trans. R. Soc. Lond. B 367, 1338–1349 (2012).
Hohwy, J. The neural correlates of consciousness: new experimental approaches needed? Conscious. Cogn. 18, 428–438 (2009).
Baars, B.J., Ramsøy, T.Z. & Laureys, S. Brain, conscious experience and the observing self. Trends Neurosci. 26, 671–675 (2003).
Dehaene, S. et al. Cerebral mechanisms of word masking and unconscious repetition priming. Nat. Neurosci. 4, 752–758 (2001).
Hebb, D.O. & Penfield, W. Human behavior after extensive bilateral removal from the frontal lobes. Arch. Neurol. Psychiatry 42, 421–438 (1940).
Frässle, S., Sommer, J., Jansen, A., Naber, M. & Einhäuser, W. Binocular rivalry: frontal activity relates to introspection and action but not to perception. J. Neurosci. 34, 1738–1747 (2014).
Kamphuisen, A., Bauer, M. & van Ee, R. No evidence for widespread synchronized networks in binocular rivalry: MEG frequency tagging entrains primarily early visual cortex. J. Vis. 8 http://dx.doi.org/10.1167/8.5.4 (2008).
Iber, C., Ancoli-Israel, S., Chesson, A. & Quan, S.F. The AASM Manual for the Scoring of Sleep and Associated Events: Rules, Terminology and Technical Specifications (American Academy of Sleep Medicine, 2007).
Delorme, A. & Makeig, S. EEGLAB: an open source toolbox for analysis of single-trial EEG dynamics including independent component analysis. J. Neurosci. Methods 134, 9–21 (2004).
Jung, T.P. et al. Removing electroencephalographic artifacts by blind source separation. Psychophysiology 37, 163–178 (2000).
Pascual-Marqui, R.D. Standardized low-resolution brain electromagnetic tomography (sLORETA): technical details. Methods Find Exp Clin Pharmacol 24 (Suppl. D), 5–12 (2002).
Huber, R., Ghilardi, M.F., Massimini, M. & Tononi, G. Local sleep and learning. Nature 430, 78–81 (2004).
Huber, R. et al. Arm immobilization causes cortical plastic changes and locally decreases sleep slow wave activity. Nat. Neurosci. 9, 1169–1176 (2006).
Nichols, T.E. & Holmes, A.P. Nonparametric permutation tests for functional neuroimaging: a primer with examples. Hum. Brain Mapp. 15, 1–25 (2002).
Rossion, B., Schiltz, C. & Crommelinck, M. The functionally defined right occipital and fusiform “face areas” discriminate novel from visually familiar faces. Neuroimage 19, 877–883 (2003).
Corbetta, M., Miezin, F.M., Shulman, G.L. & Petersen, S.E. A PET study of visuospatial attention. J. Neurosci. 13, 1202–1226 (1993).
Malhotra, P., Coulthard, E.J. & Husain, M. Role of right posterior parietal cortex in maintaining attention to spatial locations over time. Brain 132, 645–660 (2009).
Grossman, E. et al. Brain areas involved in perception of biological motion. J. Cogn. Neurosci. 12, 711–720 (2000).
Puce, A., Allison, T., Bentin, S., Gore, J.C. & McCarthy, G. Temporal cortex activation in humans viewing eye and mouth movements. J. Neurosci. 18, 2188–2199 (1998).
Narain, C. et al. Defining a left-lateralized response specific to intelligible speech using fMRI. Cereb. Cortex 13, 1362–1368 (2003).
Gross, D.W. & Gotman, J. Correlation of high-frequency oscillations with the sleep-wake cycle and cognitive activity in humans. Neuroscience 94, 1005–1018 (1999).
Andrillon, T. et al. Sleep spindles in humans: insights from intracranial EEG and unit recordings. J. Neurosci. 31, 17821–17834 (2011).
Sirota, A., Csicsvari, J., Buhl, D. & Buzsáki, G. Communication between neocortex and hippocampus during sleep in rodents. Proc. Natl. Acad. Sci. USA 100, 2065–2069 (2003).
Seghier, M.L. Laterality index in functional MRI: methodological issues. Magn. Reson. Imaging 26, 594–601 (2008).
Renard, Y. et al. OpenViBE: an open-source software platform to design, test, and use brain-computer interfaces in real and virtual environments. Presence 19, 35–53 (2010).
Tadel, F., Baillet, S., Mosher, J.C., Pantazis, D. & Leahy, R.M. Brainstorm: a user-friendly application for MEG/EEG analysis. Comput. Intell. Neurosci. 2011, 879716 (2011).
Chumbley, J., Worsley, K., Flandin, G. & Friston, K. Topological FDR for neuroimaging. Neuroimage 49, 3057–3064 (2010).
Keren, A.S., Yuval-Greenberg, S. & Deouell, L.Y. Saccadic spike potentials in gamma-band EEG: characterization, detection and suppression. Neuroimage 49, 2248–2263 (2010).
Muthukumaraswamy, S.D. High-frequency brain activity and muscle artifacts in MEG/EEG: a review and recommendations. Front. Hum. Neurosci. 7, 138 (2013).
The authors thank D. Bachhuber, L. Barbosa, R. Benca, E. Carrera, A. Castelnovo, A. Cayo, C. Cirelli, R. Davidson, C. Funk, M. Gevelinger, J. Harris, A. Mensen, P. Nori, R. Smith, L. Vuillaume, S. Yu, C. Zennig and our undergraduate research assistants for help with data collection, sleep scoring, technical assistance and discussions. This work was supported by NIH/NCCAM P01AT004952 (to G.T.), NIH/NIMH 5P20MH077967 (to G.T.), Tiny Blue Dot Inc. grant MSN196438/AAC1335 (to G.T.), Swiss National Science Foundation Grants 139778 (to F.S.), 145571 (to F.S.) and 155120 (to L.P.), Swiss Foundation for Medical Biological Grants 151743 and 145763 (to F.S.), NIH/NINDS F32NS089348 (to B.B.), UW Medical Scientist Training Program Grant T32 GM008692 (to J.J.L.), NIH Grants MH064498 and MH095984 (to B.R.P.).
G.T. and B.R. are involved in a research study in humans supported by Philips Respironics. This study is not related to the work presented in the current manuscript.
Integrated supplementary information
Cortical distribution of t-values for the contrast between DEs and NEs at the source level for low-frequency power (1-4 Hz) in NREM sleep (20s before awakening). p<0.05 after correction for multiple comparisons (two-tailed, paired t-tests, 7 subjects, t(6) ≥ 2.45). B. Same as A for high- frequency power (25-50 Hz) in NREM sleep (two-tailed, paired t-tests, 7 subjects, t(6) ≥ 2.45).
Conjunction maps: differences and overlaps between the two contrasts (DE/NE and DEWR/NE) for low-frequency power in NREM sleep. DE/NE contrast: 32 subjects, DEWR/NE contrast 20 subjects.
Cortical distribution of t-values for the contrast between DEs and NEs at the source level for high-frequency power (25-50 Hz) in NREM sleep (20s before awakening) for experiment 1. p<0.05 after correction for multiple comparisons (two-tailed, paired t-tests, 32 subjects, t(31) > 2.04).
A. Cortical distribution of t-values for the contrast between DEWRs and NEs at the source level for high-frequency power (20-50 Hz) in NREM sleep (20s before awakening). p<0.05 after correction for multiple comparisons (two-tailed, paired t-tests, 20 subjects, t(19) > 2.09). B. Cortical distribution of unthresholded t-values for the same comparison.
Power spectral density for DE and NE, averaged over the posterior hot zone, (determined by the overlap between the DE/NE contrast in REM and NREM sleep, as shown in Figure 2B), for high- and low-frequency bands in NREM (n=32) and REM sleep (n=10). Two-tailed paired t-tests (NREM LF: t(31)= -2.98; NREM HF: t(31)= 3.46; REM LF: t(9)= -3.59; REM HF: t(9)= 3.10). Whiskers correspond to 3 standard deviations from the mean, crosses indicate values above this limit.
High-frequency power (20-50 Hz) for dream experiences (DE) and no experiences (NE) in NREM, averaged over the ROI used for prediction in experiment 3.7 subjects, paired t-test, t(6)=4.41, p=0.005, two-tailed). The asterisk indicates a significant difference (p=0.005) between DE and NE trials.
Cortical distribution of t-values for the contrast between DEs and NEs for the HF/LF power ratio in NREM sleep (20s before awakening), p<0.05 SnPM corrected (two-tailed, paired t-tests, 7 subjects). All vertices displayed a significant effect for DE>NE.
Cortical distribution of unthresholded t-values for the contrast between DEs and NEs for delta power in NREM sleep (20s before awakening) for experiments 1 (32 subjects) and 2 (7 subjects). Paired two-tailed t-tests.
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Siclari, F., Baird, B., Perogamvros, L. et al. The neural correlates of dreaming. Nat Neurosci 20, 872–878 (2017). https://doi.org/10.1038/nn.4545
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