Callow Daniel D, Won Junyeon, Pena Gabriel S, Jordan Leslie S, Arnold-Nedimala Naomi A, Kommula Yash, Nielson Kristy A, Smith J Carson
Department of Kinesiology, University of Maryland, College Park, MD, United States.
Program in Neuroscience and Cognitive Science, University of Maryland, College Park, MD, United States.
Front Aging Neurosci. 2021 Apr 8;13:645258. doi: 10.3389/fnagi.2021.645258. eCollection 2021.
Individuals with Mild Cognitive Impairment (MCI) are at an elevated risk of dementia and exhibit deficits in cognition and cortical gray matter (GM) volume, thickness, and microstructure. Meanwhile, exercise training appears to preserve brain function and macrostructure may help delay or prevent the onset of dementia in individuals with MCI. Yet, our understanding of the neurophysiological effects of exercise training in individuals with MCI remains limited. Recent work suggests that the measures of gray matter microstructure using diffusion imaging may be sensitive to early cognitive and neurophysiological changes in the aging brain. Therefore, this study is aimed to determine the effects of exercise training in cognition and cortical gray matter microstructure in individuals with MCI vs. cognitively healthy older adults. Fifteen MCI participants and 17 cognitively intact controls (HC) volunteered for a 12-week supervised walking intervention. Following the intervention, MCI and HC saw improvements in cardiorespiratory fitness, performance on Trial 1 of the Rey Auditory Verbal Learning Test (RAVLT), a measure of verbal memory, and the Controlled Oral Word Association Test (COWAT), a measure of verbal fluency. After controlling for age, a voxel-wise analysis of cortical gray matter diffusivity showed individuals with MCI exhibited greater increases in mean diffusivity (MD) in the left insular cortex than HC. This increase in MD was positively associated with improvements in COWAT performance. Additionally, after controlling for age, the voxel-wise analysis indicated a main effect of Time with both groups experiencing an increase in left insular and left and right cerebellar MD. Increases in left insular diffusivity were similarly found to be positively associated with improvements in COWAT performance in both groups, while increases in cerebellar MD were related to gains in episodic memory performance. These findings suggest that exercise training may be related to improvements in neural circuits that govern verbal fluency performance in older adults through the microstructural remodeling of cortical gray matter. Furthermore, changes in left insular cortex microstructure may be particularly relevant to improvements in verbal fluency among individuals diagnosed with MCI.
轻度认知障碍（MCI）患者患痴呆症的风险较高，并且在认知以及皮质灰质（GM）体积、厚度和微观结构方面存在缺陷。与此同时，运动训练似乎可以维持大脑功能，其宏观结构可能有助于延缓或预防MCI患者痴呆症的发作。然而，我们对运动训练对MCI患者神经生理影响的了解仍然有限。最近的研究表明，使用扩散成像测量灰质微观结构可能对衰老大脑的早期认知和神经生理变化敏感。因此，本研究旨在确定运动训练对MCI患者与认知健康的老年人在认知和皮质灰质微观结构方面的影响。15名MCI参与者和17名认知正常的对照组（HC）自愿参加了为期12周的有监督的步行干预。干预后，MCI组和HC组在心肺适能、雷伊听觉词语学习测验（RAVLT）试验1（一种言语记忆测量方法）以及受控口语词语联想测验（COWAT）（一种言语流畅性测量方法）中的表现均有所改善。在控制年龄后，对皮质灰质扩散率进行的体素分析显示，MCI患者左侧岛叶皮质的平均扩散率（MD）比HC组增加得更多。MD的这种增加与COWAT表现的改善呈正相关。此外，在控制年龄后，体素分析表明存在时间主效应，两组的左侧岛叶以及左侧和右侧小脑的MD均增加。同样发现，两组左侧岛叶扩散率的增加与COWAT表现的改善呈正相关，而小脑MD的增加与情景记忆表现的提高有关。这些发现表明，运动训练可能通过皮质灰质的微观结构重塑，与改善老年人中控制言语流畅性表现的神经回路有关。此外，左侧岛叶皮质微观结构的变化可能与被诊断为MCI的个体言语流畅性的改善特别相关。
