The human hippocampal formation can be divided into a set of cytoarchitecturally 
and functionally distinct subregions, involved in different aspects of memory 
formation. Neuroanatomical disruptions within these subregions are associated 
with several debilitating brain disorders including Alzheimer's disease, major 
depression, schizophrenia, and bipolar disorder. Multi-center brain imaging 
consortia, such as the Enhancing Neuro Imaging Genetics through Meta-Analysis 
(ENIGMA) consortium, are interested in studying disease effects on these 
subregions, and in the genetic factors that affect them. For large-scale 
studies, automated extraction and subsequent genomic association studies of 
these hippocampal subregion measures may provide additional insight. Here, we 
evaluated the test-retest reliability and transplatform reliability (1.5T versus 
3T) of the subregion segmentation module in the FreeSurfer software package 
using three independent cohorts of healthy adults, one young (Queensland Twins 
Imaging Study, N=39), another elderly (Alzheimer's Disease Neuroimaging 
Initiative, ADNI-2, N=163) and another mixed cohort of healthy and depressed 
participants (Max Planck Institute, MPIP, N=598). We also investigated agreement 
between the most recent version of this algorithm (v6.0) and an older version 
(v5.3), again using the ADNI-2 and MPIP cohorts in addition to a sample from the 
Netherlands Study for Depression and Anxiety (NESDA) (N=221). Finally, we 
estimated the heritability (h(2)) of the segmented subregion volumes using the 
full sample of young, healthy QTIM twins (N=728). Test-retest reliability was 
high for all twelve subregions in the 3T ADNI-2 sample (intraclass correlation 
coefficient (ICC)=0.70-0.97) and moderate-to-high in the 4T QTIM sample 
(ICC=0.5-0.89). Transplatform reliability was strong for eleven of the twelve 
subregions (ICC=0.66-0.96); however, the hippocampal fissure was not 
consistently reconstructed across 1.5T and 3T field strengths (ICC=0.47-0.57). 
Between-version agreement was moderate for the hippocampal tail, subiculum and 
presubiculum (ICC=0.78-0.84; Dice Similarity Coefficient (DSC)=0.55-0.70), and 
poor for all other subregions (ICC=0.34-0.81; DSC=0.28-0.51). All hippocampal 
subregion volumes were highly heritable (h(2)=0.67-0.91). Our findings indicate 
that eleven of the twelve human hippocampal subregions segmented using 
FreeSurfer version 6.0 may serve as reliable and informative quantitative 
phenotypes for future multi-site imaging genetics initiatives such as those of 
the ENIGMA consortium.