Movement Control and Neuroplasticity Research Group, Department of Movement Sciences, KU Leuven, Leuven (3000), Belgium; LBI-KU Leuven Brain Institute, Leuven (3000), Belgium.
PROVIDI Lab, Image Sciences Institute, University Medical Center Utrecht, Utrecht 3584 CX, Netherlands; Neurology Department, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht 3584 CX, Netherlands.
Neuroimage. 2021 Nov 1;241:118433. doi: 10.1016/j.neuroimage.2021.118433. Epub 2021 Jul 27.
Understanding the relationship between human brain structure and functional outcome is of critical importance in systems neuroscience. Diffusion MRI (dMRI) studies show that fractional anisotropy (FA) is predictive of motor control, underscoring the importance of white matter (WM). However, as FA is a surrogate marker of WM, we aim to shed new light on the structural underpinnings of this relationship by applying a multi-compartment microstructure model providing axonal density/radius indices. Sixteen young adults (7 males / 9 females), performed a hand/foot tapping task and a Multi Limb Reaction Time task. Furthermore, diffusion (STEAM &HARDI) and fMRI (localizer hand/foot activations) data were obtained. Sphere ROIs were placed on activation clusters with highest t value to guide interhemispheric WM tractography. Axonal radius/density indices of callosal parts intersecting with tractography were calculated from STEAM, using the diffusion-time dependent AxCaliber model, and correlated with behavior. Results indicated a possible association between larger apparent axonal radii of callosal motor fibers of the hand and higher tapping scores of both hands, and faster selection-related processing (normalized reaction) times (RTs) on diagonal limb combinations. Additionally, a trend was present for faster selection-related processing (normalized reaction) times for lower limbs being related with higher axonal density of callosal foot motor fibers, and for higher FA values of callosal motor fibers in general being related with better tapping and faster selection-related processing (normalized reaction) times. Whereas FA is sensitive in demonstrating associations with motor behavior, axon radius/density (i.e., fiber geometry) measures are promising to explain the physiological source behind the observed FA changes, contributing to deeper insights into brain-behavior interactions.
理解人类大脑结构和功能结果之间的关系在系统神经科学中至关重要。弥散磁共振成像（dMRI）研究表明，各向异性分数（FA）可预测运动控制，这突显了白质（WM）的重要性。然而，由于 FA 是 WM 的替代标志物，我们旨在通过应用提供轴突密度/半径指数的多隔室微观结构模型，为这种关系的结构基础提供新的见解。16 名年轻成年人（7 名男性/9 名女性）进行了手部/脚部敲击任务和多肢体反应时间任务。此外，还获得了弥散（STEAM 和 HARDI）和 fMRI（手部/脚部激活定位器）数据。将球体 ROI 放置在具有最高 t 值的激活簇上，以指导半球间 WM 轨迹追踪。使用依赖扩散时间的 AxCaliber 模型从 STEAM 计算穿过轨迹的胼胝体部分的轴突半径/密度指数，并与行为相关联。结果表明，手部胼胝体运动纤维的表观轴突半径较大可能与双手的敲击得分较高以及对角肢体组合的选择相关处理（归一化反应）时间（RT）较快有关。此外，下肢的选择相关处理（归一化反应）时间较快与胼胝体脚运动纤维的轴突密度较高有关，而胼胝体运动纤维的 FA 值较高通常与敲击得分较高和选择相关处理（归一化反应）时间较快有关。虽然 FA 对于证明与运动行为的关联很敏感，但轴突半径/密度（即纤维几何形状）测量对于解释观察到的 FA 变化的生理来源很有希望，有助于深入了解大脑-行为相互作用。
