Contents lists available at ScienceDirect Consciousness and Cognition journal homepage: www.elsevier.com/locate/concog Attempted induction of signalled lucid dreaming by transcranial alternating current stimulation Cloé Blanchette-Carrière a,d,1 , Sarah-Hélène Julien b,d , Claudia Picard-Deland c,d , Maude Bouchard b,d , Julie Carrier b,d , Tyna Paquette d , Tore Nielsen a,d, ⁎ a Department of Psychiatry, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada b Department of Psychology, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada c Department of Neurosciences, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada d Center for Advanced Research in Sleep Medicine, CIUSSS-NÎM – Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Blvd West, Montréal, Québec H4J 1C5, Canada ARTICLE INFO Keywords: Self-awareness Lucid dreaming Transcranial alternating current stimulation REM sleep ABSTRACT Neurophysiological correlates of self-awareness during sleep (‘lucid dreaming’) remain unclear despite their importance for clarifying the neural underpinnings of consciousness. Transcranial direct (tDC) and alternating (tAC) current stimulation during sleep have been shown to increase dream self-awareness, but these studies’ methodological weaknesses prompted us to undertake additional study. tAC stimulation was associated with signal-verified and self-rated lucid dreams—but so was the sham procedure. Situational factors may be crucial to inducing self- awareness during sleep. 1. Introduction Typical dreaming differs from waking consciousness in that it lacks accurate self-reflection; dreaming may simulate real per- ceptions, actions and emotions, but typically not awareness of the fact that these features are only simulations. Nonetheless, at times dreaming is punctuated precisely by such a wake-like self-awareness of dreaming—commonly referred to as lucid dreaming—and a limited control over the simulation may occur. This control has allowed investigators to verify lucid dreaming in real-time by instructing participants to perform pre-arranged signals, such as pendular eye movement sequences, while maintaining their REM sleep state (LaBerge, 1992). The neurophysiology of lucid dreaming remains obscure but constitutes an important step in identifying the neural correlates of consciousness more generally (Koch, Massimini, Boly, & Tononi, 2016). Early lucid dreaming studies showed inconsistent EEG changes such as elevated alpha (Tyson, Ogilvie, & Hunt, 1984) or beta power (Holzinger, LaBerge, & Levitan, 2006); more recent work suggests elevated frontal 40 Hz power (Mota-Rolim, Erlacher, Tort, Araujo, & Ribeiro, 2010; Voss, Holzmann, Tuin, & Hobson, 2009). Brain imaging confirms elevated frontal activity during lucid dreaming (Dresler et al., 2012), but also elevations in parietal and occipito-temporal regions. Such changes may signify that lucid dreaming is a unique hybrid consciousness state that combines REM sleep and wakefulness components (Voss et al., 2009). These correlational studies were recently superseded by two experimental demonstrations that frontal electrical stimulation https://doi.org/10.1016/j.concog.2020.102957 Received 14 January 2020; Received in revised form 17 April 2020; Accepted 24 April 2020 ⁎ Corresponding author at: Center for Advanced Research in Sleep Medicine, CIUSSS-NÎM – Hôpital du Sacré-Cœur de Montréal, 5400 Gouin Blvd West, Montréal, Québec H4J 1C5, Canada. E-mail address: tore.nielsen@umontreal.ca (T. Nielsen). 1 Present address: Department of Psychology, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada. Consciousness and Cognition 83 (2020) 102957 1053-8100/ © 2020 Elsevier Inc. All rights reserved. T