Add 'zstat' as part of task-fMRI file names

[mharms]

@glasserm @gcburgess What do you think about us adding 'zstat' explicitly as part of the summary (merged) file names that result from the task pipeline, so that we no longer have this confusing historical oddity where the 'beta' maps are indicated as such via the file name, but the 'zstat' maps are not. Should be a relatively simple code addition, but would require a willingness to adapt downstream scripts (outside of the HCP Pipelines) that may be looking for the "zstat" outputs.

[glasserm]

Isn't it already doing this?

[mharms]

No. Technically, we should also be calling the 'beta' files 'copes', because a "beta" is typically understood to refer to the parameter estimates (PEs) from the GLM itself, while contrasts can be formed from any linear combination of the betas. So, we have some copes that are identical to the betas/PEs (because the contrast is simply along the lines of [1 0 0 0 ... 0]. But other copes are the difference of the betas/PEs (i.e., contrast of [1 -1 0 0 ... 0]. That's why FSL's Feat distinguishes between pe's and cope's in its output files.

[glasserm]

Didn't you already make this change?

[mharms]

Nope.

[glasserm]

Perhaps that is in the level3 code only, but I'm happy for you to make these changes in the single subject code also.

[mharms]

Sure. I can add 'zstat' as part of the file name in the level2 code. Are you willing to change 'beta' to 'cope' as well? That would possibly require more adjustment of downstream scripts (if those "summary" merged files are getting used), and thus could possibly be more disruptive...

[glasserm]

That is okay. My task fMRI code has diverged a bit from what is in the git repo due to particular needs so it is fine if we get things converted over.

[mharms]

While we are at it, should we change the output type from dtseries to dscalar as well, so that the output type better reflects the data?

[glasserm]

Sure I think the final files are already dscalar.