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Convolution Signal Model
¥ FMRI signal we look for in each voxel is taken to be sum of the individual trial HRFs
H Stimulus timing is assumed known (or measured)
H Resulting time series (blue curves) are called the convolution of the HRF with the stimulus timing
¥ Must also allow for baseline and baseline drifting
H Convolution models only the FMRI signal changes
22 s
120 s
¥ Real data starts at and
  returns to a nonzero,
  slowly drifting baseline