[pymvpa] Searchlight sl_map = accuracy?

[Nynke van der Laan]

Hello all,
I am new to mvpa and while working through some of the searchlight
examples (more specifically, example 9.3.6 Searchlight on fMRI data),
some things were not completely clear to me.
First, what do the values in the sl_map refer to? According to the
documentation, these are the TransferErrors of the
n-foldclassification. Later on it is called an sensitivitymap. But
does this mean that it are the accuracies? (true pos + true neg/
total) or are it sensitivities? (true positive/all positives)
Second, I read that it is possible to map the values from the sl_map
back to the original dataspace. In the example the variable
masked_orig_sl_map is the sensitivity map that is mapped back into the
original dataspace. How can I save this variable as a nifti file in
order to be able to use it as an 3d-overlay for in, for example,
MRIcron or another imageviewer?
Thanks in advance for answering my questions!
Best regards,
Nynke van der Laan