Human hippocampus depth measurement and comparison in MRI
CORTEX
Stimulation of the hippocampal area does not trigger an assessable evoked potential; therefore, it is not possible to directly establish the required intensity of spTMS to reach the target. Thus, we used an indirect measure. We compared the depth of the hippocampus with the deepest M1 of the frontal lobe (foot M1) and estimated the capacity to stimulate the hippocampus based on TMS parameters that elicit MEPs in foot M1.Anonymous single-subject MRI images of the entire brain of eight healthy subjects were analyzed in this study. With the aid of MRIcro software, the coordinates of the following key locations were registered in each subject’s MRI: deepest foot cortex [Key locations represented in coronal (left) and sagittal (right) view in MRI. A. Primary foot motor cortex location and the corresponding frontal surface location. B. Most distal and proximal points of the hippocampus and corresponding temporal surface location.Each key location was identified in the right and left hemispheres. The hippocampal boundaries were defined to include the CA1 through CA4 areas of the hippocampus-proper, dentate gyrus, and subiculum in the hippocampal head in the foot M1 coronal plane. Foot cortex locations were selected based on functional MRI (fMRI) studies [