Vecchio Fabrizio, Miraglia Francesca, Curcio Giuseppe, Altavilla Riccardo, Scrascia Federica, Giambattistelli Federica, Quattrocchi Carlo Cosimo, Bramanti Placido, Vernieri Fabrizio, Rossini Paolo Maria
Brain Connectivity Laboratory, IRCCS San Raffaele Pisana, Rome, Italy.
Department of Life, Health and Environmental Sciences, University of L'Aquila, L'Aquila, Italy.
J Alzheimers Dis. 2015;45(3):745-56. doi: 10.3233/JAD-142484.
A relatively new approach to brain function in neuroscience is the "functional connectivity", namely the synchrony in time of activity in anatomically-distinct but functionally-collaborating brain regions. On the other hand, diffusion tensor imaging (DTI) is a recently developed magnetic resonance imaging (MRI)-based technique with the capability to detect brain structural connection with fractional anisotropy (FA) identification. FA decrease has been observed in the corpus callosum of subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI, an AD prodromal stage). Corpus callosum splenium DTI abnormalities are thought to be associated with functional disconnections among cortical areas. This study aimed to investigate possible correlations between structural damage, measured by MRI-DTI, and functional abnormalities of brain integration, measured by characteristic path length detected in resting state EEG source activity (40 participants: 9 healthy controls, 10 MCI, 10 mild AD, 11 moderate AD). For each subject, undirected and weighted brain network was built to evaluate graph core measures. eLORETA lagged linear connectivity values were used as weight of the edges of the network. Results showed that callosal FA reduction is associated to a loss of brain interhemispheric functional connectivity characterized by increased delta and decreased alpha path length. These findings suggest that "global" (average network shortest path length representing an index of how efficient is the information transfer between two parts of the network) functional measure can reflect the reduction of fiber connecting the two hemispheres as revealed by DTI analysis and also anticipate in time this structural loss.
神经科学中一种相对较新的研究脑功能的方法是“功能连接性”，即解剖结构上不同但功能协作的脑区活动在时间上的同步性。另一方面，扩散张量成像（DTI）是一种最近开发的基于磁共振成像（MRI）的技术，能够通过分数各向异性（FA）识别来检测脑结构连接。在患有阿尔茨海默病（AD）和轻度认知障碍（MCI，AD前驱阶段）的受试者的胼胝体中观察到FA降低。胼胝体压部的DTI异常被认为与皮质区域之间的功能断开有关。本研究旨在调查通过MRI-DTI测量的结构损伤与通过静息态脑电图源活动中检测到的特征路径长度测量的脑整合功能异常之间的可能相关性（40名参与者：9名健康对照者、10名MCI患者、10名轻度AD患者、11名中度AD患者）。对于每个受试者，构建无向加权脑网络以评估图核心指标。eLORETA滞后线性连接值用作网络边的权重。结果表明，胼胝体FA降低与脑半球间功能连接性丧失有关，其特征是δ波增加和α波路径长度减少。这些发现表明，“全局”（平均网络最短路径长度代表网络两部分之间信息传递效率的指标）功能测量可以反映DTI分析所揭示的连接两个半球的纤维减少情况，并且还能及时预测这种结构损失。
