<AFNI>Task based process

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3dClustSim

• Estimate the probability of false positive (noise-only) clusters.
• 3dClustSim computes a cluster-size threshold for a given voxel-wise p-value threshold such that the probability of anything surviving the dual thresholds is at some given level (specified by the ‘-athr’ option).
• real FMRI data does not actually have a Gaussian-shaped ACF(AutoCorrelation Function), so the estimated ACF is then fit (in 3dFWHMx) to a mixed model (Gaussian plus mono-exponential) of the form

Reference: https://afni.nimh.nih.gov/pub/dist/doc/program_help/3dClustSim.html

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• Suggested Choices for Basis Functions:
  
  • deconvolution (variable-shape regression): TENT(b,c,n)
  • regression (fixed-shape regression): GAM, BLOCK(d,p) or BLOCK(d)