Dear all,

I am planning to run separate VBM regression analysis with gray matter volume in two very different populations (young and elderly subjects). Depending on results, I may be interested in comparing regression slopes between the two groups. My question is: should I run Dartel with all subjects of the two population, although most of the analysis (sex differences, correlations with performance, etc)  will be performed in each sample separately? I am not sure if combining the two samples in the same Dartel template may affect structural brain changes obtained within each separate group, especially when groups are so different (young vs. elderly).

Looking forward to your comments.

Many thanks in in advance.

Best regards,