¥ HRF is the idealization of measurable FMRI signal change responding to a
single activation cycle (up and down) from a stimulus
in a voxel
Response to brief activation (< 1
s):
¥ delay of 1-2 s
¥ rise time of 4-5 s
¥ fall time of 4-6 s
¥ model equation:
¥ h(t ) is signal change t seconds after activation
1
Brief Activation
Hemodynamic
Response Function (HRF)