¥ Usually have more than one class of stimulus or activation in an
experiment
H e.g., want to see size of Òface
activationÓ vis-ˆ-vis Òhouse activationÓ; or,
ÒwhatÓ vs. ÒwhereÓ activity
¥ Need to model each separate class of stimulus with a separate response
function r1(t ), r2(t ), r3(t ), É.
H Each rj(t ) is based on the stimulus timing for activity in class number j
H Calculate
a bj amplitude = amount of rj(t ) in
voxel data time series Z(t )
H Contrast bs to see which voxels have differential activation levels under
different stimulus conditions
² e.g., statistical test on the question b1Ðb2 = 0 ?