afni.nimh.nih.gov

Hi Lz,

The extents mask restricts the result to only those
voxels that have data at every time point. This is
specifically because of motion, particularly when
combined with warping the result to a larger box.
At the edges, some voxels get time series that are
based on the motion. At such a voxel, some TRs have
valid data, some are identically zero, as they came
from outside the EPI box.

If volreg were an independent step, the extents mask
would not be so important.

- rick