Short Synopsis of the final ROCÝanalysis
of single subject study
(accepted to Neuroimage october 1998)
1) block study design
-
AB...A design (start and and with the same condition to minilmalize
effects of monotonic drift)
-
optimal task block length - 15-20 sec (assuming 2-3 sec of possible
delay, may be less for sensory motor studies), this result is independent
from the length of imaging series.
2) choice of preprocessing steps
-
spatial smoothing init_gaus_filt(1)
the default value of 1 applies the gaussian filter of half widthh at half
maximum equal to pixel size
-
high-pass filtering (a.k.a Chris filter) at 0.35 of the stimulus frequency
(Chris default value is 0.5, so you have to use it with increased number
of OnOff Blocks ChrisFilt(OnOffNUmber*1.4)
other available options:
-
temporal normalization - does NOT help
-
polynominal (linear, quadratic ...) trend_subtr
drift removal help (but less than high-pass filter)
3) Statistics (applied to a SINGLE run)
-
Cross-correlation, t_statistic, and Mann-Whitney
are best
-
signal change (%), Fourier and split statistics
are BAD
-
skew correction is helpful only for unbalanced
AB..AB design
4) Spatial smoothing
-
Initial Gaussian smoothing is BETTER that final
cluster filtering
-
multifiltering (adding maps with and without smoothing
is BEST (but complicated)
5) Between identical run consolidation
-
Mean of individal t-maps is better than taking
lowest or highest value (it has an additional advantage of being insensitive
to changes in number of runs).
-
Running statistics without regard to breaks in
imaging runs is BAD
-
averaging runs works BEST (assuming that runs
are IDENTICAL)Ý this can be applied by applying theÝ postprocessing function
ColapseSeries
-
this function reduces data set, to images collected
in the first data series, those images are replaced by averages of images
collected at the same time in all imaging series