¥ 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