Since the time series was thresholded into a binary spike time series in step 1, the ROI average is indeed the fraction of voxels that are spikes at each time point. It is not the average spikiness, but the average of the spiked voxels.
For example, if at some time point 40% of the ROI voxels are 1.5 and 60% are 3, the binarized time series will have 40% of the voxels at 0 and 60% at 1, since they are thresholded at 2.5. And then the ROI average will be 0.6, the fraction of voxels that seem "bad". Note that the values in this average time series are always in [0,1].
Does this seem reasonable?
- rick
