Exploring the role of white matter connectivity in cortex maturation

The maturation of the cortical gray matter (GM) and white matter (WM) are described as sequential processes following multiple, but distinct rules. However, neither the mechanisms driving brain maturation processes, nor the relationship between GM and WM maturation are well understood. Here we use connectomics and two MRI measures reflecting maturation related changes in cerebral microstructure, namely the Apparent Diffusion Coefficient (ADC) and the T1 relaxation time (T1), to study brain development. We report that the advancement of GM and WM maturation are inter-related and depend on the underlying brain connectivity architecture. Particularly, GM regions and their incident WM connections show corresponding maturation levels, which is also observed for GM regions connected through a WM tract. Based on these observations, we propose a simple computational model supporting a key role for the connectome in propagating maturation signals sequentially from external stimuli, through primary sensory structures to higher order functional cortices.大脑皮层灰质（GM）与白质（WM）的成熟过程被描述为遵循多重独特规则的连续进程。然而，目前学界对于驱动大脑成熟进程的机制，以及灰质与白质成熟之间的内在关联，仍未得到充分阐释。本研究借助连接组学（connectomics），以及两项可反映大脑微观结构成熟相关变化的磁共振成像（MRI）指标——表观扩散系数（ADC）与T1弛豫时间（T1），开展脑发育相关研究。我们发现，灰质与白质的成熟进程存在相互关联，且依赖于底层的大脑连接架构。具体而言，灰质区域及其所关联的白质连接呈现出匹配的成熟水平，这一现象同样存在于通过白质束相连的灰质区域中。基于上述观测结果，我们提出了一款简洁的计算模型，该模型支持连接组在将成熟信号从外部刺激依次传递至初级感觉结构，再到高级功能皮层的过程中发挥关键作用。