PowerPoint Presentation - Time Series Analysis in AFNI

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Equations: Single Response Function

• In each voxel, fit data Zn to a curve of the form

Zn » a + b×tn + b×rn for n=0,1,…,N-1 (N=# time pts)

• a, b, b are unknown parameters to be calculated in each voxel

• a,b are “nuisance” baseline parameters

• b is amplitude of r(t ) in data = “how much” BOLD

• Baseline model might be more complicated for long (> 150 s) continuous imaging runs:

• 150 < T < 300 s: a+b×t+c×t 2

• Longer: a+b×t+c×t 2 + éT/200ù low frequency components

• Might also include as extra baseline components the estimated subject head movement time series, in order to remove residual contamination from such artifacts