¥ Serial correlation does not appreciably
impact the activation magnitudes (b s) estimated using 3dDeconvolve
(= Ordinary Least Squares solution)
¥ Group activation maps made from
combining these b s using 3dANOVA,
3dLME,
etc., are essentially the same using 3dDeconvolve
or 3dREMLfit
(= Generalized Least Squares solution)
Ø In other
words, there is no need to
re-run old group analyses to see if allowing for serial
correlation will change the results
¥ Thresholded individual
subject activation maps are potentially affected, depending on the task timing and on the
scanner
H The biggest effect of serial (AKA
temporal ) correlation—when this correlation is
significant—is on the estimates of the variance
of the individual subjectsÕ b s
H If the variance is under-estimated using
3dDeconvolve, then the individual subject t- and F-statistics
will be over-estimated
H Individual subject variances and
statistics are not usually carried forward to the group
analysis level
o Since
inter-subject variance is much larger than intra-subject variance
H Thus, group results are only marginally
affected by serial correlation