PMC

Microstructural correlates of memory performance. Scatter plots are illustrated for composite scores of immediate recall, delayed recall, and delayed recognition (see Methods), versus each of the main microstructural metrics: CA1-SRLM width, CA1-SP width, DG/CA3 cross-sectional area, and ERC width. Statistics are shown only for significant correlations; also see . CA1-SRLM and CA1-SP widths were determined using a semi-automated method (see ).

Semi-automated stratal width determination. (A) Superimposed on an image of the right hippocampus in one patient is a user-specified line through the CA1-SRLM (open circles). The thick white line is the spline fit to the user-specified line, and thin white lines delineate the direction of the orthogonal vectors derived from the algorithm described in Methods. (B) Average T2 signal intensity (in relative units) is plotted against distance from the user-specified line (in pixels). Squares represent measured values, and the solid line is a spline fit through those points, as described in Methods. The dashed line and circles correspond to the first derivative. The width of the stratum of interest is defined as the distance between the peak and the trough of this first derivative.

7 T hippocampal microstructural imaging. (A–P) Serial oblique coronal slices, zoomed to the right hippocampus, are illustrated for one of the patients enrolled in this study. Slices are arranged anterior to posterior, using the same scale represented by the bar in panel (A). (Q) Higher magnification view of panel (I), illustrating how subfields are demarcated. Areas containing dense collections of neuronal cell bodies (e.g., CA1-SP) appear bright on this T2-weighted image, whereas neuropil areas (e.g., CA1-SRLM), which contain dense tangles of axons, dendrites, and synapses, appear relatively hypointense. DG, dentate gyrus; CA1–3, cornus ammonis subfields 1–3; SP, stratum pyramidale; SRLM, stratum radiatum/stratum lacunosum-moleculare; sub, subiculum. (R) Higher magnification of the parahippocampal gyrus from panel (E), illustrating how the entorhinal cortex (ERC) is demarcated.