Functional Brain MRI Activation and Exercise

生活方式干预和老年人独立性(LIFE)试点试验的结果之一是，干预组的数字符号替代测试(DSST)分数(用于测试加工速度和执行控制功能)随着时间的推移保持稳定，而对照组的数字符号替换测试分数在同一时期下降。最近出现的证据表明，与不锻炼的人相比，参加体育锻炼的老年人更有可能保持较高的认知功能，而不太可能患上痴呆症或其他功能障碍。有氧肌肉活动可能会增加脑血流量，而更大的脑氧量反过来可以防止与年龄相关的神经元退化过程，有助于延缓大脑功能的下降。与对照组相比，生活干预项目增加的有氧活动水平可能对脑血管有积极的影响。这种增强的脑血管效应可能是导致与年龄相关的神经元死亡延迟的原因之一，因此可以解释两组之间测量的DSST评分的差异。了解这种有氧干预是否与大脑功能的这种变化有关是很重要的，因为大脑在控制流动性方面发挥着重要作用。 大脑的完整性与机动性有关。在老年人中，执行控制领域的认知表现，特别是DSST得分，与更快的步态速度和更好的几项行动能力指标相关，与其他与健康相关的行动障碍风险因素无关。除了大脑功能，MRI测量的大脑结构也有明显的方面，这也与运动能力有关。Rosanos博士的研究小组已经证明，大脑连通性疾病的负担(例如，脑白质高信号体积)，以及选定活动相关区域神经元萎缩的严重程度，都与步速和平衡困难有关，并且这些关联与混杂因素无关。 功能性脑MRI是衡量脑功能完整性的可靠工具。脑成像研究表明，参与执行控制功能的区域的神经元激活和新陈代谢随着年龄的增长而下降，这种神经元信号的下降与认知能力的下降有关。罗萨诺博士此前曾使用功能性脑磁共振成像(FMRI)技术测量了一组老年人的神经元激活强度。她发现，认知正常的老年人在执行执行控制功能任务时，在背外侧前额叶皮质、后顶叶皮质和前扣带皮质有更大的激活，例如修改后的Stroop任务28，来自这些区域的fMRI信号与修改后的Stroop测试的实际表现密切相关。 基于这些发现，我们同时获得了脑功能磁共振成像和1年的身体功能(400米步行和SPPB)和认知功能测量(数字符号替代试验(DSST)、Stroop和滕氏改良最低状态考试(MMSE))的随访数据。假设干预组在执行控制功能区有更高的fMRI信号激活，更高的长期执行控制功能得分(如dsst测量)和更好的行动能力。它还假设，这些联系将独立于由MMSE测量的全球认知功能。这一发现表明，这种类型的有氧干预与更大的神经元激活有关。

One of the results of the Lifestyle Interventions and Independence for Elders (LIFE) pilot trial was that the digit symbol substitution test (DSST) score, a test of processing speed and executive control function, remained stable over time in the intervention group, while the DSST score of the control group declined over the same period of time. There is recent emerging evidence that older adults who are engaged in physical exercise are more likely to maintain high cognitive function and less likely to develop dementia or other functional impairments compared to those who do not exercise. Aerobic muscular activity may increase cerebral blood flow, and greater cerebral oxygenation can in turn prevent the age-related processes of neuronal degeneration and help delay the brain functional decline. It is possible that the increased level of aerobic activity from the LIFE intervention program had positive cerebrovascular effects in the intervention vs. the control group. Such enhanced cerebrovascular effects may have contributed to delay in age-related neuronal death and would thus explain the difference in DSST scores that were measured between the two groups. It is important to understand whether this type of aerobic intervention is associated with such changes in brain functioning, because the brain plays an important role in controlling mobility. Brain integrity is associated with mobility. In older adults, cognitive performance in executive control domains, and specifically the DSST score, are associated with faster gait speed and with better performance on several mobility measures, independently of other health-related risk factors for mobility impairment. In addition to brain function, there are distinct aspects of brain structure, as measured on MRI, which are also associated with motor performance. Dr. Rosanos research group has shown that the burden of brain connectivity disease (e.g. white matter hyperintensities volume), and the severity of neuronal atrophy in selected mobility-related areas, are both associated with gait speed and balance difficultied, and that these associations are independent of confounders. Functional brain MRI is a reliable tool to measure the brain functional integrity. Brain imaging studies have shown that the neuronal activation and metabolism in regions that are involved in executive control function declines with older age, and that this declining neuronal signal is associated with declining cognitive performance. Dr. Rosano has previously measured the intensity of neuronal activation in a population of older adults by using the functional brain MRI (fMRI) technique. She found that cognitively normal older adults have greater activation in the dorsolateral prefrontal cortex, in the posterior parietal cortex and in the anterior cingulated cortex while they are engaged in executive control function tasks, such as the modified Stroop task 28 and the fMRI signal from these regions was strongly correlated with the actual performance on the modified Stroop test. Based on these discoveries, we have acquired brain fMRI concurrently with 1 year follow-up data on physical function (400 meter walk and SPPB) and measures of cognitive function (digit symbol substitution test (DSST), Stroop and Teng Modified Minimental State Exam (MMSE). It is hypothesized that the intervention group has greater fMRI signal activation in the executive control function regions, higher long term executive control function scores (as measured by DSST) and better mobility measures than the control group. It is also hypothesized that these associations will be independent of global cognitive function, as measured by the MMSE. This finding would suggest that this type of aerobic intervention is linked with greater neuronal activation.