Hello Freesurfer gurus,

We have two samples of approximately n~125-150 whose T1s were collected on the same scanner with the same acquisiton, except for a difference in head coil (8 vs 32 channel) and processed with different Freesurfer versions (v5.3.0 and v. 6.0.0). Both also had the FreeSurfer segmentation of hippocampal subfields v 6.0.0 applied. We would like your guidance about combining their data if possible to maximize sample size.

What would your suggestion be for hypothesis testing? Can we combine the samples - for example to test moderators of hippocampal x age relationships, using simply a covariate to account for the differences in acquisition/Freesurfer processing (in addition to the usual sociodemographic and estimated intracranial volume covariates)? 

OR is that problematic and would you instead suggest keeping them separate and using one as a replication sample?