Rotman Research Institute, Baycrest, 3560 Bathurst Street, Toronto, ON, M6A 2E1, Canada.
Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada.
BMC Neurosci. 2019 Jul 31;20(1):37. doi: 10.1186/s12868-019-0518-4.
Cardiovascular conditions contribute to brain volume loss, reduced cerebrovascular health, and increased dementia risk in aging adults. Altered hippocampal connectivity has also been observed in individuals with cardiovascular conditions, yet the functional consequences of these changes remain unclear. In the present study, we collected functional magnetic resonance imaging data during memory encoding and used a psychophysiological interaction analysis to examine whether cardiovascular burden, indexed using the Framingham risk score, was associated with encoding-related hippocampal connectivity and task performance in cognitively-intact older adults between 65 and 85 years of age. Our goal was to better understand the early functional consequences of vascular and metabolic dysfunction in those at risk for cognitive decline.
High Framingham risk scores were associated with lower total brain volumes. In addition, those with high Framingham risk scores showed an altered relationship between left hippocampal-medial prefrontal coupling and task performance compared to those with low Framingham risk scores. Specifically, we found a significant interaction of Framingham risk and learning on connectivity between the left hippocampus and primarily left midline prefrontal regions comprising the left ventral anterior cingulate cortex and medial prefrontal cortex. Those with lower Framingham risk scores showed a pattern of weaker connectivity between left hippocampal and medial prefrontal regions associated with better task performance. Those with higher Framingham risk scores showed the opposite pattern; stronger connectivity was associated with better performance.
Findings from the current study show that amongst older adults with cardiovascular conditions, higher Framingham risk is associated with lower brain volume and altered left hippocampal-medial prefrontal coupling during task performance compared to those with lower Framingham risk scores. This may reflect a compensatory mechanism in support of memory function and suggests that older adults with elevated cardiovascular risk are vulnerable to early Alzheimer disease-like dysfunction within the episodic memory system.
心血管状况会导致大脑体积缩小、脑血管健康状况恶化，并增加老年人患痴呆症的风险。在患有心血管疾病的个体中也观察到海马连接的改变，但这些变化的功能后果仍不清楚。在本研究中，我们在记忆编码期间收集了功能磁共振成像数据，并使用心理生理交互分析来检查 Framingham 风险评分（一种心血管风险指数）是否与认知健全的 65 至 85 岁老年人的编码相关海马连接和任务表现相关。我们的目标是更好地了解血管和代谢功能障碍在认知能力下降风险人群中的早期功能后果。
高 Framingham 风险评分与总脑容量较低有关。此外，与低 Framingham 风险评分者相比，高 Framingham 风险评分者的左海马-内侧前额叶耦合与任务表现之间的关系发生改变。具体而言，我们发现 Framingham 风险与学习之间存在显著的交互作用，这种交互作用影响了左海马与主要包括左前扣带回腹侧和内侧前额叶的左侧中线前额叶区域之间的连接。低 Framingham 风险评分者的左海马和内侧前额叶区域之间的连接较弱，与任务表现较好相关。高 Framingham 风险评分者则相反，较强的连接与更好的表现相关。
本研究的结果表明，在患有心血管疾病的老年人中，与 Framingham 风险较低者相比，较高的 Framingham 风险与较低的脑容量和任务表现期间左海马-内侧前额叶耦合改变有关。这可能反映了支持记忆功能的代偿机制，并表明心血管风险较高的老年人易患早期阿尔茨海默病样功能障碍的情景记忆系统。
