Resting state fMRI and Probabilistic DTI demonstrate that the Greatest Functional and Structural Connectivity in the Hand Motor Homunculus Occurs in the area of the Thumb.

Brain Connect. 2018 Jul 10;:

Authors: Hamidian S, Vachha B, Jenabi M, Karimi S, Young RJ, Holodny AI, Peck KK

Abstract
BACKGROUND AND PURPOSE: The primary hand motor region is classically believed to be in the "hand knob" area in the precentral gyrus (PCG). However, hand motor task-based activation is often localized outside this area. The purpose of this study is to investigate the structural and functional connectivity driven by different seed locations corresponding to the little, index, and thumb in the PCG using probabilistic diffusion tractography (PDT) and resting state fMRI (rfMRI).
METHODS: Twelve healthy subjects had three ROIs placed the left PCG: lateral to the hand knob (thumb area), within the hand knob (index finger area), and medial to the hand knob (little finger area). Connectivity maps were generated using PDT and rfMRI. Individual and group level analyses were performed.
RESULT: Results show that the greatest hand motor connectivity between both hemispheres was obtained using the ROI positioned just lateral to the hand knob in the PCG (the thumb area). The number of connected voxels in the PCG between the two hemispheres was greatest in the lateral-most ROI (the thumb area): 279 compared to 13 for the medial-most ROI and 9 for and the central hand knob ROI. Similarly, the highest white matter connectivity between the two hemispheres resulted from the ROI placed in the lateral portion of PCG (p<0.003).
CONCLUSIONS: The maximal functional and structural connectivity of the hand motor area between hemispheres occurs in the thumb area, located laterally at the "hand knob". Thus, this location appears optimal for rfMRI and PDT seeding of the motor area.

PMID: 29987948 [PubMed - as supplied by publisher]