AFNI Idea - Connectivity in Task datasets

To get task-based connectivity on an ROI level:
1) Compute IM betas for each block/event
2) Test the collection of IM betas for nonzero mean (for each task class)
3) Threshold and cluster the voxels
4) Between each pair of clusters/ROIs, compute the correlation of IM betas in some way

Result is an activation map (from 3) and a 'functional connectivty' map between the active clusters. No dynamics, of course, or causality.

Significance of correlations? What's the null hypothesis here? Not just that there is no activation at all. Must be some activation + no-ROI-correlation hypothesis.