title: Co-activated yet disconnected-Neural correlates of eye closures when trying to stay awake.
abstract: Spontaneous eye-closures that herald sleep onset become more frequent when we are sleep deprived. Although these are typically associated with decreased responsiveness to external stimuli, it is less clear what occurs in the brain at these transitions to drowsiness and light sleep. To investigate this, task-free fMRI of sleep-deprived participants was acquired. BOLD activity associated with periods of spontaneously occurring eye closures were marked and analyzed. We observed concurrent and extensive hypnagogic co-activation of the extrastriate visual, auditory, and somatosensory cortices as well as the default mode network, consistent with internal sensory activity without external stimulation. Co-activation of fronto-parietal areas known to mediate attentional control could correspond with participants resisting sleep or additional engagement of mental imagery. This constellation of signal changes differed from those elicited by cued eye closures of similar duration and distribution in the same, rested participants. They also differ from signal changes associated with mind-wandering and consolidated light sleep. Concurrent with the observed event-related changes, eye closures elicited additional reduction in functional connectivity within nodes of the DMN and DAN, superposed on already reduced connectivity associated with sleep deprivation. There was concurrent deactivation of the thalamus during eye-closure during the sleep-deprived state but almost similar changes occurred in the well-rested state that may also be relevant. These findings highlight the dynamic shifts in brain activity and connectivity at border between wakefulness and sleep.
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Ju Lynn
authors.initials: JL
authors.lastname: Ong
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Danyang
authors.initials: D
authors.lastname: Kong
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Tiffany T Y
authors.initials: TT
authors.lastname: Chia
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Jesisca
authors.initials: J
authors.lastname: Tandi
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore; Department of Electrical & Computer Engineering, Clinical Imaging Research Centre and Singapore Institute for Neurotechnology, National University of Singapore, Singapore.
authors.forename: B T
authors.initials: BT
authors.lastname: Thomas Yeo
authors.affiliation: Center for Cognitive Neuroscience, Neuroscience & Behavioral Disorders Program, Duke-NUS Graduate Medical School, Singapore. Electronic address: michael.chee@duke-nus.edu.sg.
authors.forename: Michael W L
authors.initials: MW
authors.lastname: Chee
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D005123:Eye; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D012892:Sleep Deprivation / Q000503:physiopathology; D012894:Sleep Stages / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*; D055815:Young Adult
keywords: Eye closure; Hypnagogia; Sleep deprivation; Sleep mentation; fMRI