Dear Jeff,

thanks!

What I thought is that CONN completely removes volumes of high motion and then replaces them with interpolated data. But apparently this is not the case. So if I understood you correctly, CONN does not remove these volumes, but uses the bad time points to create regressors for nuisance regression, is that correct?

However, I am still a bit confused. I thought the terms "censoring" and "scrubbing" both describe the same procedure, so what is the difference?


Cheers,
Sascha

Hi Sascha,

I am currently learning more about this myself. My general understanding is that Conn uses ART to identify the outlier scans based on parameters you select and then uses those scans as nuisance regressors in the first-level analysis. ART also produces a mask of the outliers that can be used as an explicit mask to avoid any influence of the outliers in the first level analysis. (I got this information from the ART code included in the ART download. It is attached) I don't see that ART does any interpolation.

In Spiegel et al (2014), scrubbing means the same thing as censoring, and it means "applying temporal masks to remove high motion volumes", and "In motion censoring, volumes in which head motion exceeded a threshold (a)re withheld from GLM estimation." It sounds like Conn (through ART) does both motion regression (if you enter the regressors into the analysis) and motion censoring, i.e., applies a temporal mask. However, to make the temporal mask, in the commented out part of the file with the code, it states "(in SPM you will also need to modify the defaults in order to skip the implicit masking operation, e.g. set defaults.mask.thresh = -inf)

Of course any or all of this could be wrong. I would appreciate any comments!

Best,

Mary