Schlichting, M.L.*, Mack, M.L.*, Guarino, K.F., & Preston, A.R. (2019). [Comparison of semi-automated hippocampal subfield segmentation methods in a pediatric sample.][1] *NeuroImage*, *191*, 49-67. Downloadable Atlases -- - **ASHS_separated.tar.gz**: [ASHS][4] atlas with ROIs for CA1, dentate gyrus, CA23, and subiculum. - **ASHS_combined.tar.gz**: Same as above but with combined dentate gyrus and CA23 ROI. - **ANTs_grouptemplate.tar.gz**: Group template generated with [ANTs][3] and manually segmented ROIs for CA1, dentate gyrus, CA23, and subiculum. **Note:** Anatomical volumes (whole brain T1 and high-resolution T2) and ROI segmentations based on manual protocol and four semi-automated methods are also available in the segmentations folder. Project Summary -- Episodic memory function has been shown to depend critically on the hippocampus. This region is made up of a number of subfields, which differ in both cytoarchitectural features and functional roles in the mature brain. Recent neuroimaging work in children and adolescents has suggested that these regions may undergo different developmental trajectories—a fact that has important implications for how we think about learning and memory processes in these populations. Despite the growing research interest in hippocampal structure and function at the subfield level in healthy young adults, comparatively fewer studies have been carried out looking at subfield development. One barrier to studying these questions has been that manual segmentation of hippocampal subfields—considered by many to be the “gold standard” approach for defining these regions—is laborious and can be infeasible for large cross-sectional or longitudinal studies of cognitive development. Moreover, manual segmentation requires some subjectivity and is not impervious to bias or error. In a developmental sample of individuals spanning 6-30 years, we compared the performance of two semi-automated segmentation approaches, Advanced Normalization Tools (ANTs) and Automated Segmentation of Hippocampal Subfields (ASHS), to manual subfield delineation on each individual by a single expert rater. Across several quantitative metrics, we found negligible differences in subfield reliability across the child, adolescent, and adult age groups, suggesting that these methods can be reliability applied to developmental studies. We conclude that ASHS outperforms ANTs overall, and is thus preferable for analyses carried out in individual subject space. However, we underscore that ANTs is also acceptable, and may be well-suited for analyses requiring normalization to a single group template (e.g., voxelwise analyses across a wide age range). Previous work has validated the use of such methods in healthy young adults, as well as several special populations such as older adults and those suffering from mild cognitive impairment. Our results extend these previous findings to show that ASHS and ANTs can also be used in pediatric populations as young as six. [1]: https://www.sciencedirect.com/science/article/pii/S1053811919300473 [2]: https://www.sciencedirect.com/science/article/pii/S1053811919300473 [3]: http://stnava.github.io/ANTs/ [4]: https://sites.google.com/site/hipposubfields/home