Fig. 3.

Volumetric measurements of the hippocampus from 13 different studies. (ROI volumes were obtained via an optimized multi-atlas, multi-warping consensus method (Doshi et al., 2016), which topped the challenge of (Asman, 2013)). Inter-study differences render it difficult to combine data into a single training set. Application of statistical harmonization methods (taking into consideration various covariates, such as age and sex, as well as the nonlinearity in brain aging trajectories) must be applied, prior to being able to leverage the power of such large databases for machine learning methods.