title: Local awakening: regional reorganizations of brain oscillations after sleep.
abstract: Brain functions express rhythmic fluctuations accompanied by sleep and wakefulness each day, but how sleep regulates brain rhythms remains unclear. Following the dose-dependent local sleep concept, two succeeding questions emerge: (1) is the sleep regulation a network-specific process; and (2) is the awakening state dependent on the previous sleep stages? To answer the questions, we conducted simultaneous EEG and fMRI recordings over 22 healthy male participants, along pre-sleep, nocturnal sleep and awakening. Using paired comparisons between awakening and pre-sleep conditions, three scenarios of the regional specificity were demonstrated on awakening: (1) the default-mode and hippocampal networks maintained similar connectivity and spectral power; (2) the sensorimotor network presented reduced connectivity and spectral power; and (3) the thalamus demonstrated substantially enhanced connectivity to the neo-cortex with decreased spectral power. With regard to the stage effect, the deep sleep group had significant changes in both functional connectivity and spectral power on awakening, whereas the indices of light sleep group remained relatively quiescent after sleep. The phenomena implied that slow-wave sleep could be key to rebooting the BOLD fluctuations after sleep. In conclusion, the regional specificity and the stage effect were verified in support of the local awakening concept, indicating that sleep regulation leads to the reorganization of brain networks upon awakening.
authors: Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.
authors: Pei-Jung
authors: PJ
authors: Tsai
authors: Department of Medical Imaging and Radiological Sciences, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors: Sharon Chia-Ju
authors: SC
authors: Chen
authors: Department of Psychiatry, Kaohsiung Medical University Chung-Ho Memorial Hospital, Kaohsiung, Taiwan.
authors: Chun-Yao
authors: CY
authors: Hsu
authors: Graduate Institute of Biomedical Engineering, National Central University, Taoyuan, Taiwan. Electronic address: restingfmri@gmail.com.
authors: Changwei W
authors: CW
authors: Wu
authors: Department of Medical Imaging, Cheng Hsin General Hospital, Taipei, Taiwan.
authors: Yu-Chin
authors: YC
authors: Wu
authors: Department of Research and Education, Taipei City Hospital, Taipei, Taiwan.
authors: Ching-Sui
authors: CS
authors: Hung
authors: Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan.
authors: Albert C
authors: AC
authors: Yang
authors: Department of Radiology, Hualien Armed Forces General Hospital, Hualien, Taiwan.
authors: Po-Yu
authors: PY
authors: Liu
authors: Department of Radiology, New Jersey Medical School, Newark, NJ, USA.
authors: Bharat
authors: B
authors: Biswal
authors: Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei, Taiwan.
authors: Ching-Po
authors: CP
authors: Lin
mesh_terms: D001921:Brain / Q000502:physiology*; D001931:Brain Mapping; D004569:Electroencephalography; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000502:physiology; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*
keywords: Functional connectivity; Local awakening; Local sleep; Simultaneous EEG–fMRI recordings; Spectral power; Thalamo-cortical connectivity