PowerPoint Presentation - Using AFNI Interactively

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• 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)