mALFF Z or T values

Submitted by Rafael on Wed, 04/20/2011 - 21:33

Dear REST pros

When calculating ALFF or mALFF are the resulting images raw (power) values or Z-transformed values? The manual states Z-transformation only for conneticity (r) maps. How could I get Z-maps? Group means heve been shown in the literature a Z-maps as well as T-maps (ones sample T-test against 1). What would be appropriate for ALFF and what for mALFF? Z-transformation does not allow for generalisation to the population level, I think.

Thanks a lot for your support

Rafael

Submitted by dongzy08 on Sun, 04/24/2011 - 09:17

ALFF and mALFF are calculated basing on the raw values, you do not need to do the Z-transformation.

Submitted by YAN Chao-Gan on Tue, 04/26/2011 - 13:40

People usually use Fisher's Z-transformation to covert r value into z value to improve the normality.
For ALFF value, there is not such a transformation. However, some people will subtract the mean value across all the voxels and then divide by the STD to perform a "Z-transformation".