afni.nimh.nih.gov

After you extract the 503 time series into a text .1D file (as described in my earlier post), you could correlate them with any other dataset, not just the one they were taken from. So you could downsample the original dataset. Which (unless it was already blurred) should be done with a little bit of blurring first (3dmerge -1blur_fwhm 4 ..., or 3dBlurInMask -FWHM 4 ...) followed by 3dresample.