title: Higher-order contrast functions improve performance of independent component analysis of fMRI data.
abstract: OBJECTIVE
  To evaluate the performance of different contrast functions used in Independent Component Analysis (ICA) of functional magnetic resonance imaging (fMRI) data at low signal-to-noise ratio (SNR), present in fMRI paradigms such as resting-state acquisitions.
  
  
  METHODS
  Metrics were defined to estimate both the accuracy and robustness of contrast functions under varying source distributions. Simulations were performed to compare the performance of lower-order (such as ln cosh) to higher-order (such as kurtosis) contrast functions using Laplacian source distributions corrupted with Gaussian noise. The ln cosh and kurtosis contrast functions were also compared using resting-state fMRI data from 10 normal adult volunteers.
  
  
  RESULTS
  Higher-order contrast functions provided superior performance compared to lower-order contrast functions in the evaluation of metrics and via the simulations in the presence of a significant amount of noise. The performance of kurtosis was not statistically significantly different from that of a theoretically optimized contrast function. The choice of contrast function was found to result in substantial (R < 0.9) differences in 40% of the components found from the resting-state fMRI data.
  
  
  CONCLUSIONS
  The use of higher-order contrast functions, such as kurtosis, may provide superior performance in ICA analysis of fMRI data with low SNR.
authors.affiliation: Pediatric Neuroimaging Research Consortium, Children's Hospital Medical Center, Cincinnati, Ohio, USA. Vince.Schmithorst@cchmc.org
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Schmithorst
mesh_terms: D000465:Algorithms; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D025341:Principal Component Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity