title: Phase synchronization analysis of prefrontal tissue oxyhemoglobin oscillations in elderly subjects with cerebral infarction.
abstract: OBJECTIVE
  This study aims to assess the phase relationship of prefrontal tissue oxyhemoglobin oscillations using wavelet phase coherence analysis of cerebral Delta [HbO₂] signals in cerebral infarction (CI) patients during the resting state.
  
  
  METHODS
  Continuous recordings of near-infrared spectroscopy signals were obtained from the left and right prefrontal lobes in 21 subjects with CI (Group CI, age: 76.6 ± 8.5 yr) and 21 healthy elderly subjects (Group Healthy, age: 69.0 ± 7.4 yr) during the resting state. The Group CI was further divide into two groups: CI with hypertension and CI without hypertension. The phase synchronization between left and right prefrontal Delta [HbO₂] oscillations in four frequency intervals (I, 0.6-2 Hz; II, 0.145-0.6 Hz; III, 0.052-0.145 Hz; and IV, 0.021-0.052 Hz) was analyzed using wavelet phase coherence method.
  
  
  RESULTS
  The phase coherences in intervals III and IV were significantly lower in CI with hypertension than in healthy elderly subjects (F = 12.974, p = 0.001 for III and F = 10.073, p = 0.004 for interval IV). The phase coherence of CI without hypertension in interval III was significantly lower than in healthy elderly subjects (F = 9.909, p = 0.004). Also, the phase coherence in interval IV was significantly lower in CI with hypertension than in CI without hypertension (F = 5.665, p = 0.028). Also, the phase agreement in interval IV showed evident difference between Group CI with hypertension and without hypertension.
  
  
  CONCLUSIONS
  The difference in phase characteristics of prefrontal tissue oxyhemoglobin oscillations between the CI patients and healthy elderly indicates altered phase synchronization. Moreover, the CI combined with hypertension would aggravate this process. This study provides new insight into the phase dynamics of cerebral oxygenation and may be useful in assessing the risk for stroke.
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Han
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Zengyong
authors.initials: Z
authors.lastname: Li
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Yuanjin
authors.initials: Y
authors.lastname: Gao
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Wenhao
authors.initials: W
authors.lastname: Li
authors.affiliation: Hospital of Shandong University, Jinan 250061, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Xin
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Qitao
authors.initials: Q
authors.lastname: Tan
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Manyu
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Key Laboratory of High Efficiency and Clean Mechanical Manufacture, School of Mechanical Engineering, Shandong University, Jinan 250061, China.
authors.forename: Yixun
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000368:Aged; D000465:Algorithms; D002544:Cerebral Infarction / Q000503:physiopathology*; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D008297:Male; D010108:Oxyhemoglobins / Q000378:metabolism*; D010507:Periodicity; D017397:Prefrontal Cortex / Q000503:physiopathology*; D012146:Rest; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D010108:Oxyhemoglobins