Metzler-Baddeley Claudia, Foley Sonya, de Santis Silvia, Charron Cyril, Hampshire Adam, Caeyenberghs Karen, Jones Derek K
Cardiff University, Brain Research Imaging Centre (CUBRIC).
University Miguel Hernandez, Alicante, Spain.
J Cogn Neurosci. 2017 Sep;29(9):1509-1520. doi: 10.1162/jocn_a_01127. Epub 2017 Mar 30.
Adaptive working memory (WM) training may lead to cognitive benefits that are associated with white matter plasticity in parietofrontal networks, but the underlying mechanisms remain poorly understood. We investigated white matter microstructural changes after adaptive WM training relative to a nonadaptive comparison group. Microstructural changes were studied in the superior longitudinal fasciculus, the main parietofrontal connection, and the cingulum bundle as a comparison pathway. MRI-based metrics were the myelin water fraction and longitudinal relaxation rate R from multicomponent relaxometry (captured with the mcDESPOT approach) as proxy metrics of myelin, the restricted volume fraction from the composite hindered and restricted model of diffusion as an estimate of axon morphology, and fractional anisotropy and radial diffusivity from diffusion tensor imaging. PCA was used for dimensionality reduction. Adaptive training was associated with benefits in a "WM capacity" component and increases in a microstructural component (increases in R, restricted volume fraction, fractional anisotropy, and reduced radial diffusivity) that predominantly loaded on changes in the right dorsolateral superior longitudinal fasciculus and the left parahippocampal cingulum. In contrast, nonadaptive comparison activities were associated with the opposite pattern of reductions in WM capacity and microstructure. No group differences were observed for the myelin water fraction metric suggesting that R was a more sensitive "myelin" index. These results demonstrate task complexity and location-specific white matter microstructural changes that are consistent with tissue alterations underlying myelination in response to training.
适应性工作记忆（WM）训练可能会带来与顶叶额叶网络中白质可塑性相关的认知益处，但其潜在机制仍知之甚少。我们研究了适应性WM训练后相对于非适应性对照组的白质微观结构变化。在主要的顶叶额叶连接——上纵束以及作为对照通路的扣带束中研究微观结构变化。基于MRI的指标包括：多组分弛豫测量法（采用mcDESPOT方法采集）得到的髓磷脂水分数和纵向弛豫率R，作为髓磷脂的替代指标；复合阻碍与受限扩散模型得到的受限体积分数，作为轴突形态的估计值；以及扩散张量成像得到的分数各向异性和径向扩散率。主成分分析（PCA）用于降维。适应性训练与“WM容量”成分的改善以及微观结构成分的增加（R增加、受限体积分数增加、分数各向异性增加以及径向扩散率降低）相关，这些变化主要集中在右侧背外侧上纵束和左侧海马旁扣带束的改变上。相比之下，非适应性对照活动与WM容量和微观结构的相反变化模式相关。在髓磷脂水分数指标上未观察到组间差异，这表明R是一个更敏感的“髓磷脂”指标。这些结果表明，任务复杂性和特定位置的白质微观结构变化与训练引起的髓鞘形成所涉及的组织改变一致。
