Three-dimensional probabilistic maps of mesial temporal lobe structures in children and adolescents’ brains.

Description: The hippocampus and the adjacent perirhinal, entorhinal, temporopolar and parahippocampal cortices are interconnected in a hierarchical MTL system crucial for memory processes. A probabilistic description of the anatomical location and spatial variability of MTL cortices in the child and adolescent brain would help to assess structure-function relationships. The rhinal sulcus (RS) and the collateral sulcus (CS) that border MTL cortices and influence their morphology have never been described in these populations. In this study, we identified the aforementioned structures on magnetic resonance images of 38 healthy subjects aged 7-17 years old. We showed that (1) RS-CS conformation (as observed in adults) has already reached adult-like maturity in children and adolescents; (2) RS-CS conformation is an additional factor of variability in the MTL that is not explained by other variables such as age, sex and brain volume; (3) RS-SC conformation was not associated with differences of location of MTL sulci. For the first time, MTL morphology in children and adolescent was described in a systematic and probabilistic approach that mapped all the structures of the MTL system while taking sulcal morphology into account. Our results, with the probabilistic maps described here being freely available for download, will help to understand the anatomy of this region and help functional and clinical studies to accurately test structure-function hypotheses in the MTL during development.