Rotman Research Institute, Baycrest Health Sciences, Toronto M6A 2E1, Ontario
Department of Psychology, University of Toronto, Toronto M5S 3G3, Ontario.
eNeuro. 2020 May 20;7(3). doi: 10.1523/ENEURO.0290-19.2020. Print 2020 May/Jun.
Local brain signal variability [SD of the BOLD signal (SD]] correlates with age and cognitive performance, and recently differentiated Alzheimer's disease (AD) patients from healthy controls. However, it is unknown whether changes to SD precede diagnosis of AD or mild cognitive impairment. We compared ostensibly healthy older adult humans who scored below the recommended threshold on the Montreal cognitive assessment (MoCA) and who showed reduced medial temporal lobe (MTL) volume in a previous study ("at-risk" group, = 20), with healthy older adults who scored within the normal range on the MoCA ("control" group, = 20). Using multivariate partial least-squares analysis we assessed the correlations between SD and age, MoCA score, global fractional anisotropy, global mean diffusivity, and four cognitive factors. Greater SD in the MTL and occipital cortex positively correlated with performance on cognitive control/speed tasks but negatively correlated with memory scores in the control group. These relations were weaker in the at-risk group. A analysis assessed associations between MTL volumes and SD in both groups. This revealed a negative correlation, most robust in the at-risk group, between MTL SD and MTL subregion volumetry, particularly the entorhinal and parahippocampal regions. Together, these results suggest that the association between SD and cognition differs between the at-risk and control groups, which may be because of lower MTL volumes in the at-risk group. Our data indicate relations between MTL SD and cognition may be helpful in understanding brain differences in individuals who may be at risk for further cognitive decline.
局部脑信号变异性[BOLD 信号的标准差（SD）]与年龄和认知表现相关，最近还能将阿尔茨海默病（AD）患者与健康对照者区分开来。然而，尚不清楚 SD 的变化是否先于 AD 或轻度认知障碍的诊断。我们比较了在之前的研究中 Montreal 认知评估（MoCA）得分低于推荐阈值且内侧颞叶（MTL）体积减小的看似健康的老年成年人（“有风险”组，n=20）与 MoCA 得分正常范围内的健康老年成年人（“对照组”，n=20）。使用多元偏最小二乘分析，我们评估了 SD 与年龄、MoCA 评分、整体各向异性分数、整体平均弥散度以及四个认知因素之间的相关性。MTL 和枕叶皮层的 SD 越大，与认知控制/速度任务的表现呈正相关，但与对照组的记忆评分呈负相关。在有风险组中，这些关系较弱。相关性分析评估了两组 MTL 体积与 SD 之间的关联。这表明，MTL 的 SD 与 MTL 各分区体积之间存在负相关，在有风险组中最为明显，尤其是在海马旁回和内嗅皮质区。综上所述，这些结果表明，SD 与认知之间的关联在有风险组和对照组之间存在差异，这可能是由于有风险组的 MTL 体积较小所致。我们的数据表明，MTL SD 与认知之间的关系可能有助于理解可能进一步认知下降的个体的大脑差异。
