Hi,

I performed an atlas-based lesion-symptom mapping analysis by considering a custom ROI with NiiStat that revealed a significant region.

When overlaying the thresholded map on an MNI template and the atlas however, only a fraction of the map cover the custom ROI, but also additional other ROIs. What is the interpretation of this finding?

Furthermore, the results were repeated for a subsample, revealing exactly the same thresholded map just with a slightly lower Z-score. 

Does this custom ROI approach for one ROI test only for this ROI?

If so, why does the threholded map include other ROIs?

Could this be due to an offset during reslicing?

Any support is very much appreciated.