title: WASICA: An effective wavelet-shrinkage based ICA model for brain fMRI data analysis.
abstract: BACKGROUND
  Researches declared that the super-Gaussian property contributed to the success of some spatial independent component analysis (ICA) algorithms in brain fMRI source separation (e.g., Infomax and FastICA), which implied that sparse approximation transforming the sources (super-Gaussian or Gaussian-like) with stronger super-Gaussian feature would possibly improve the separation performance of these algorithms.
  
  
  METHODS
  This paper presented a novel wavelet-shrinkage based ICA (WASICA) model, an extension of our previous SACICA, for single-subject analysis. In contrast, two main aspects had been effectively enhanced: (1) sparse approximation coefficients set formation, made up of two sub-procedures: the wavelet-shrinkage of wavelet packet (WP) tree nodes, and the automatic nodes selection and integration based on the relative WP energy; (2) ICA-based decomposition and reconstruction, composed of temporal dynamics extraction using ICA, WP reconstruction based on the sparse approximation coefficients set and least-square-based functional networks reconstruction.
  
  
  RESULTS
  The wavelet-shrinkage and the automatic nodes selection and integration simultaneously transformed both the mixtures and underlying sources into effective sparse approximation coefficients sets, exhibiting stronger super-Gaussian distribution; WP projected-back approximation with nuisance-exclusion contributed to networks reconstruction.
  
  
  METHODS
  Simulation 1 revealed WASICA successfully recovered super-Gaussian and some Gaussian-like sources. Simulation 2 and hybrid data experiments showed that WASICA with good temporal performance had stronger source recovery ability and signal detection sensitivity spatially than FastICA, Infomax and SACICA did; the higher intra-consistency in task-related experiments denoted WASICA occupied stronger spatial robustness against smooth kernels.
  
  
  CONCLUSIONS
  WASICA was a promising brain signal separation model with charming spatial-temporal performance.
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China.
authors: Nizhuan
authors: N
authors: Wang
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China. Electronic address: zwmcd@yahoo.com.
authors: Weiming
authors: W
authors: Zeng
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China.
authors: Yingchao
authors: Y
authors: Shi
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China.
authors: Tianlong
authors: T
authors: Ren
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China.
authors: Yanshan
authors: Y
authors: Jing
authors: Lab of Digital Image and Intelligent Computation, Shanghai Maritime University, Shanghai 201306, China.
authors: Jun
authors: J
authors: Yin
authors: Department of Neurology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, China. Electronic address: yangjiajunfzy@sina.com.
authors: Jiajun
authors: J
authors: Yang
mesh_terms: D000465:Algorithms; D001921:Brain / Q000098:blood supply*; D001931:Brain Mapping; D003198:Computer Simulation; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical; D016011:Normal Distribution; D010100:Oxygen / Q000097:blood; D025341:Principal Component Analysis; D015203:Reproducibility of Results
chemical_list: D010100:Oxygen
keywords: ICA; Sparse approximation; Wavelet packet decomposition; Wavelet shrinkage; fMRI