The MTL200: a surface-based, probabilistic atlas of the medial temporal lobe.

The human medial temporal lobe (MTL) includes a number of cortical regions surrounding the hippocampus implicated in long-term memory and high-level perception, including temporopolar cortex (TPC), entorhinal cortex (ERC), perirhinal cortex (PRC), and parahippocampal cortex (PHC). A critical prerequisite to studying the function of these areas is to define their anatomical boundaries. While several atlases or segmentations methods for automated boundary definition exist, they have limitations: 1) they are derived from small sample sizes; 2) most do not include TPC; and 3) they are volumetric rather than surface-based and are therefore not straightforward to use for surface-based analysis of MRI data. Here we present the MTL200: a surface-based, probabilistic atlas of MTL regions TPC, ERC, PRC, and PHC. The atlas is derived from hand drawings of regions based on gross anatomical features corresponding to cytoarchitectonic boundaries, using anatomical MRI data from 200 human participants. This work provides a valuable tool for researchers studying the anatomy and function of MTL regions, particularly the poorly characterized area TPC.