> Is the first basis function of the SPMG2 analysis (sub-brick[0]) the activation
> removing the effect of the reaction time (becuase reaction time is run as a
> second regressor) or is the first basis sub-brick showing the activation regardless
> of the effect from other regressors like reaction time.

Using your result as an example:

# -- At sub-brick #66 'dual_hit#0_Coef' datum type is float: -20.3359 to 16.6942
# -- At sub-brick #68 'dual_hit#1_Coef' datum type is float: -45.7975 to 52.2615
# -- At sub-brick #70 'dual_hit#2_Coef' datum type is float: -6.18825 to 14.4791
# -- At sub-brick #72 'dual_hit#3_Coef' datum type is float: -26.8796 to 29.3508

the major amplitude effect from the 1st basis function in SPMG2 is sub-brick #66, and its RT modulation effect is sub-brick #70. The word "removing" in your phrase "removing the effect of the reaction time" is a misunderstanding. You can't remove the RT effect: what sub-brick #66 shows is the BOLD response amplitude that corresponds to the average RT value of this current. And the average RT value may vary to some extent across subjects, which may have impact on your group analysis strategy. For example, does the average RT value vary significantly across subjects? If so, it may warrants considering the average RT values as an explanatory variable at group level.

Gang