After selecting the desired processing stream and modifying the parameter setting, as shown in Section ProcStreamEdit & ProcStreamOptionsGUI, you can run the processing stream by following these steps:

1. Select a processing element you wish to calculate in the Current Processing Element window, then click the Calculate button to run the processing stream for the selected processing element.

2. If you want to calculate the hemodynamic response at a subject level, select the Subj element in the Current Processing Element window and click the Calculate button. Then Homer3 will automatically calculate every run element in this subject folder, also calculate the mean hemodynamic response for this subject.

3. Similarly, to calculate the hemodynamic response at a group level, select the group element in the Current Processing Element window and click the Calculate button.

Once the calculation is completed, a groupResults.mat file will be generated, containing the HRFs for all conditions and channels of every subject in the currently selected group.