help > Discrepancy between NiiStat and MRIcron NPM
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Nov 3, 2017 02:11 AM | Juan Dominguez
Discrepancy between NiiStat and MRIcron NPM
Hello,
Signs of Z scores I am getting when running VLSM analysis in NiiStat and MRIcron NPM are reversed. Areas of significance are almost identical but the Z scores are positive in MRIcron NPM and negative in NiiStat. I have used the same design/parameters and behavioural scores in both cases. The documentation of NiiStat and MRIcron would indicate behavioural scores are interpreted the same in both packages (higher scores mean better performance) and therefore I would expect the sign of Z scores in both packages to coincide.
Could you please provide clarification on this issue?
I thank you in advance for your help.
Best,
Juan
Signs of Z scores I am getting when running VLSM analysis in NiiStat and MRIcron NPM are reversed. Areas of significance are almost identical but the Z scores are positive in MRIcron NPM and negative in NiiStat. I have used the same design/parameters and behavioural scores in both cases. The documentation of NiiStat and MRIcron would indicate behavioural scores are interpreted the same in both packages (higher scores mean better performance) and therefore I would expect the sign of Z scores in both packages to coincide.
Could you please provide clarification on this issue?
I thank you in advance for your help.
Best,
Juan
Jun 21, 2018 04:06 PM | Chris Rorden
RE: Discrepancy between NiiStat and MRIcron NPM
1.) Please refer to the NiIStat notes: the polarity of NiiStat is
reverse of VLSM/NPM. Rather, NiiStat follows the standard
statistical convention that a positive association means that a
brighter image correlates with higher behavioral scores. We tend to
draw lesions as bright voxels (1) on a black (0) background. The
reason for the change is that NiiStat is designed for many
modalities (CBF, MD, FA) and therefore keeping the standard
statistical mode makes sense
https://www.nitrc.org/plugins/mwiki/index.php/niistat:MainPage#Notes
https://www.nitrc.org/plugins/mwiki/index.php/niistat:MainPage#Notes