Dear FSL group,

We have created masks of ACC and amygdalar subregions in MNI-space for conducting resting-state connectivity analysis. In order to allow time course extraction, these masks were registered to native space using FSL's FLIRT. However, the registration increases the spatial extent of the masks in native space, thereby diminishing the spatial specificity/accuracy of the masks. We used FLIRT with applyxfm option and the registration matrix file standard2example_func.mat, generated by FEAT during preprocessing

Could you be so kind and explain why this alteration occurs and how one should deal with this issue, given that the spatial specificity/accuracy of the masks is pivotal to adequate time course extraction and subsequent functional connectivity analysis.

Look forward to your response.

Best,
Mark Olivetti