You can save the pairwise correlations between all voxels.
The histogram is essentially taking a correlation map (for
some voxel), and converting it to a histogram. To see every
voxel pair, using the volumetric method.
The point of the histogram is to see frequencies per correlation
range. One bin per voxel would not be useful. Some bins
would have zero values, some one, some many.
Anyway, I think you just want to look at the correlation volumes.
- rick