title: [Functional connectivity analysis of super acute cerebral ischemia in rats: a resting-state functional MRI empirical study].
abstract: OBJECTIVE
  To investigate the change of low-frequency blood-oxygenation-level-dependent fluctuation (LFBF) after cerebral ischemia by functional connectivity analysis in the resting state.
  
  
  METHODS
  Super acute stroke rat-models with middle cerebral artery occlusion (MCAO) were employed in this study. Spontaneous fluctuations were recorded using a series of gradient-recalled echo-planar imaging (EPI) images before creation of the MCAO, and the same scan protocols were duplicated at the time of 60 min, 2 h after creation of the MCAO. FMRI signal time series from the different ROIs of ischemic cortex and normal cortex were preprocessed and low pass filtered. After preprocessing, the serial fMRI data was obtained by fast Fourier transformation to calculate the amplitude of the low-frequency fluctuations. Meanwhile, time course signal changes from a seed voxel of normal cortex were correlated with every voxel in the brain. Statistical analysis was performed across all rats to determine the extent of spatial correlation between regions.
  
  
  RESULTS
  The amplitude of LFBF in the ischemic cortex between 0.01 and 0.1 Hz was lightly decreased during the super acute ischemic stroke. Howerever, the amplitude of LFBF in contralateral cortex was increased after 2 hours. Spatial distribution of LFBF, from cross-correlation analysis, indicates that the substantial inter-hemispheric synchrony of ischemic region was decreased and of contralateral cortex was enhanced during the super acute ischemic stroke.
  
  
  CONCLUSIONS
  The contrast behavior of the resting state BOLD signal fluctuations and a intra-hemispheric symmetry in the LFBF with similar phase characteristics in most other regions during super acute ischemic stroke can be implied a new approach to detect the physiological activity functions and the distinct resting neural networks after the acute ischemic stroke takes place.
authors: Department of Radiology, Zhongda Hospital, Medical School of Southeast University, Nanjing 210009, China.
authors: Qun-li
authors: QL
authors: Yao
authors: Hong-ying
authors: HY
authors: Zhang
authors: Fang
authors: F
authors: Fang
authors: Hui
authors: H
authors: Yu
authors: Yi
authors: Y
authors: Zhang
authors: Gao-jun
authors: GJ
authors: Teng