Figure 1.

Stability and consistency of hippocampal parcellations. (A) Stable organizational patterns were found for right and left hippocampus for cluster solutions 2–4 estimated with split-half cross-validation. All clusterings reached very high stability >0.9 adjusted Rand Index. (B) Cross-sample consistency of lower cluster solutions measured with the adjusted Rand Index. Despite overall high stability, the simple parcellation schemes 2–4 were also very consistent >0.6 across datasets and within age/disease-specific groups (e.g. young, elderly) suggesting biological relevance in those differentiations. Cluster solution 3 was exceptionally useful to study age and disease-related patterns, because this scheme demonstrated not only high within age/disease similarity but to some extent also across age/disease groups indicating relatedness, which did not apply for cluster solution 4. In contrast cluster solution 2 showed very high similarity independent of age/disease and dataset suggesting on the one hand a robust biological differentiation, but on the other hand a less flexible scheme to represent lifespan and pathological alterations. Box plots with median, 1.5 interquartile range (IQR), min. Q1–1.5×IQR, max. Q3 + 1.5 × IQR.