¥Goal: Manually select Regions of Interest (ROIs) based on
anatomical structures, then analyze
functional datasets within these regions
HE.g., Someone doing
a study on emotion may want to draw an ROI mask that includes the amygdala
only in order to analyze the voxels that fall within that brain region
HThis method relies
on Ôa prioriÕ assumptions about localization of brain function
¥Alternative procedure for
selection of ROIs: Analyze functional
dataset for entire brain first, then focus on geometrically connected
clusters of ÔactivityÕ (supra-threshold voxels in
some functional statistical map)
Hi.e., analyze the
entire brain first and then pinpoint interesting areas of activity and do further
analyses on those areas (3dclust or 3dmerge can assist you in finding
those larger ÒblobsÓ or clusters of activity)
åEven with this
method, you might want to manually adjust the ROIs
¥ROIs are stored as regular
AFNI datasets; it is only the user (you) that decides whether a
particular dataset is a ROI mask
HNonzero voxels are
ÒinÓ the mask; zero voxels are ÒoutsideÓ