Abstract：
The hippocampal networks support multiple cognitive functions and may have biological roles and functions in pathological cognitive aging (PCA) and its associated diseases, which have not been explored. In the current study, a total of 116 older adults with 39 normal controls (NC) (mean age: 52.3 ± 13.64 years; 16 females), 39 mild cognitive impairment (MCI) (mean age: 68.15 ± 9.28 years, 14 females), and 38 dementia (mean age: 73.82 ± 8.06 years, 8 females) were included. The within-hippocampal subfields and the cortico-hippocampal circuits were assessed via a micro-structural similarity network approach using T1w/T2w ratio and regional gray matter tissue probability maps, respectively. An analysis of covariance was conducted to identify between-group differences in structural similarities among hippocampal subfields. The partial correlation analyses were performed to associate changes in micro-structural similarities with cognitive performance in the three groups, controlling the effect of age, sex, education, and cerebral small-vessel disease. Compared with the NC, an altered T1w/T2w ratio similarity between left CA3 and left subiculum was observed in the mild cognitive impairment (MCI) and dementia. The left CA3 was the most impaired region correlated with deteriorated cognitive performance. Using these regions as seeds for GM similarity comparisons between hippocampal subfields and cortical regions, group differences were observed primarily between the left subiculum and several cortical regions. By utilizing T1w/T2w ratio as a proxy measure for myelin content, our data suggest that the imbalanced synaptic weights within hippocampal CA3 provide a substrate to explain the abnormal firing characteristics of hippocampal neurons in PCA. Furthermore, our work depicts specific brain structural characteristics of normal and pathological cognitive aging and suggests a potential mechanism for cognitive aging heterogeneity.
摘要：
海马网络支持多种认知功能，在病理性认知衰老（PCA）及其相关疾病中可能具有生物学作用和功能。没有被探索过。在目前的研究中,共有116名老年人和39名正常对照（NC）（平均年龄：52.3±13.64岁；16名女性），39名轻度认知障碍（MCI）（平均年龄：68.15±9.28岁，14名女性），和38痴呆症（平均年龄：73.82±8.06岁，包括8名女性）。使用T1w/T2w比率和区域灰质组织概率图，通过微结构相似性网络方法评估海马内亚场和皮质-海马回路，分别。进行协方差分析以确定海马子场之间结构相似性的组间差异。进行了部分相关分析，以将三组的微观结构相似性的变化与认知表现相关联，控制年龄的影响，性别,教育,和脑小血管疾病。与NC相比,在轻度认知障碍（MCI）和痴呆患者中，观察到左CA3和左下膜之间的T1w/T2w比值相似性改变。左侧CA3是与认知能力下降相关的最受损区域。使用这些区域作为海马子场和皮质区域之间的转基因相似性比较的种子，组差异主要在左下膜和几个皮质区域之间观察到。通过利用T1w/T2w比率作为髓鞘含量的替代量度，我们的数据表明,海马CA3中突触重量的不平衡为解释PCA中海马神经元异常放电特征提供了基础.此外，我们的工作描述了正常和病理性认知老化的特定脑结构特征,并提示了认知老化异质性的潜在机制.
