title: Effects of Sleep Deprivation on Phase Synchronization as Assessed by Wavelet Phase Coherence Analysis of Prefrontal Tissue Oxyhemoglobin Signals.
abstract: OBJECTIVE
  To reveal the physiological mechanism of the decline in cognitive function after sleep deprivation, a within-subject study was performed to assess sleep deprivation effects on phase synchronization, as revealed by wavelet phase coherence (WPCO) analysis of prefrontal tissue oxyhemoglobin signals.
  
  
  METHODS
  Twenty subjects (10 male and 10 female, 25.5 ± 3.5 years old) were recruited to participate in two tests: one without sleep deprivation (group A) and the other with 24 h of sleep deprivation (group B). Before the test, each subject underwent a subjective evaluation using visual analog scales. A cognitive task was performed by judging three random numbers. Continuous recordings of the near-infrared spectroscopy (NIRS) signals were obtained from both the left and right prefrontal lobes during rest, task, and post-task periods. The WPCO of cerebral Delta [HbO2] signals were analyzed for these three periods for both groups A and B.
  
  
  RESULTS
  Six frequency intervals were defined: I: 0.6-2 Hz (cardiac activity), II: 0.145-0.6 Hz (respiratory activity), III: 0.052-0.145 Hz (myogenic activity), IV: 0.021-0.052 Hz (neurogenic activity), V: 0.0095-0.021 Hz (nitric oxide related endothelial activity) and VI: 0.005-0.0095 Hz (non-nitric oxide related endothelial activity). WPCO in intervals III (F = 5.955, p = 0.02) and V (F = 4.7, p = 0.037) was significantly lower in group B than in group A at rest. During the task period, WPCO in intervals III (F = 5.175, p = 0.029) and IV (F = 4.585, p = 0.039) was significantly lower in group B compared with group A. In the post-task recovery period, the WPCO in interval III (F = 6.125, p = 0.02) was significantly lower in group B compared with group A. Reaction time was significantly prolonged, and the accuracy rate and F1 score both declined after sleep deprivation.
  
  
  CONCLUSIONS
  The decline in WPCO after sleep deprivation indicates reduced phase synchronization between left and right prefrontal oxyhemoglobin oscillations, which may contribute to the diminished cognitive function.
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan, P.R. China.
authors.forename: Lingguo
authors.initials: L
authors.lastname: Bu
authors.affiliation: Interdisciplinary Division of Biomedical Engineering, Faculty of Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, SAR P.R. China.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan, P.R. China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Li
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan, P.R. China.
authors.forename: Fangyi
authors.initials: F
authors.lastname: Li
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan, P.R. China.
authors.forename: Heshan
authors.initials: H
authors.lastname: Liu
authors.affiliation: Key Laboratory of Rehabilitation Aids Technology and System of the Ministry of Civil Affairs, National Research Center for Rehabilitation Technical Aids, Beijing, P.R. China.
authors.forename: Zengyong
authors.initials: Z
authors.lastname: Li
mesh_terms: D000328:Adult; D003071:Cognition; D003344:Cortical Synchronization / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism*; D017397:Prefrontal Cortex / Q000503:physiopathology*; D011930:Reaction Time; D012892:Sleep Deprivation / Q000503:physiopathology*; D064232:Visual Analog Scale; D058067:Wavelet Analysis
chemical_list: D010108:Oxyhemoglobins