Acosta-Franco J Alejandro, Little Graham, Beaulieu Christian
Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
Department of Computer Science, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
Imaging Neurosci (Camb). 2025 Aug 20;3. doi: 10.1162/IMAG.a.115. eCollection 2025.
The human cortex undergoes significant macrostructural and microstructural changes across the lifespan, which can be assessed using high-resolution diffusion tensor imaging (DTI). In healthy individuals, diffusion is typically greater perpendicular to the cortical surface, aligning with neuronal bodies and apical dendrites. This study examined DTI metrics in 190 healthy individuals (ages 5-74 years) to characterize normative cortical changes across neurodevelopment and aging. Whole-brain DTI data were acquired with 1.5 mm isotropic resolution and a b-value of 1000 s/mm² acquired in only 3:36 minutes at 3T. Cortical segmentation was performed exclusively on diffusion images to yield thickness, radiality, fractional anisotropy (FA), mean (MD), axial (AD), and radial diffusivity (RD) in total cortex as well as five lobes and were compared versus age. Cortical thickness decreased exponentially which differed from the diffusion metric cross-sectional age trajectories. FA, MD, AD, and RD exhibited u-shaped trajectories reaching minimum values in adulthood (~20-40 years). In contrast, radiality showed a cubic pattern, declining in childhood, stabilizing from 20-55 years, then decreasing again after 55, with the largest early-life changes in the temporal and occipital lobes and later-life declines in the frontal and parietal lobes. Steeper childhood DTI changes may reflect increased myelination of tangential fibers, as well as the growth of neuronal axons, somata, and dendrites, while elderly changes likely indicate reduced cell body density and radius. This study provides a baseline for future research into neurodevelopment and neurodegenerative diseases across the lifespan.
人类大脑皮层在整个生命周期中会经历显著的宏观结构和微观结构变化，这些变化可以通过高分辨率扩散张量成像（DTI）进行评估。在健康个体中，扩散通常在垂直于皮层表面的方向上更大，与神经元体和顶端树突排列一致。本研究检查了190名健康个体（年龄5 - 74岁）的DTI指标，以表征神经发育和衰老过程中正常的皮层变化。全脑DTI数据以1.5毫米各向同性分辨率采集，b值为1000 s/mm²，在3T下仅用3分36秒即可采集完成。仅在扩散图像上进行皮层分割，以得出整个皮层以及五个脑叶的厚度、径向性、分数各向异性（FA）、平均扩散率（MD）、轴向扩散率（AD）和径向扩散率（RD），并与年龄进行比较。皮层厚度呈指数下降，这与扩散指标的横断面年龄轨迹不同。FA、MD、AD和RD呈现出U形轨迹，在成年期（约20 - 40岁）达到最小值。相比之下，径向性呈现出三次方模式，在儿童期下降，在20 - 55岁之间稳定，然后在55岁之后再次下降，颞叶和枕叶在生命早期变化最大，额叶和顶叶在生命后期下降。儿童期DTI变化更显著可能反映了切向纤维髓鞘化增加，以及神经元轴突、细胞体和树突的生长，而老年期的变化可能表明细胞体密度和半径减小。本研究为未来对整个生命周期的神经发育和神经退行性疾病的研究提供了基线。
