fMRI unit, Neurology department, Hadassah Medical Center and Faculty of Medicine, Hebrew University of Jerusalem, Israel.
fMRI unit, Neurology department, Hadassah Medical Center and Faculty of Medicine, Hebrew University of Jerusalem, Israel.
J Neurol Sci. 2023 Nov 15;454:120826. doi: 10.1016/j.jns.2023.120826. Epub 2023 Oct 5.
Posterior Cortical Atrophy (PCA), a visual variant of Alzheimer's disease, initially manifests with higher-order visual disorders and parieto/temporo-occipital atrophy. Recent studies have shown remote functional impairment in both distant brain networks and along the calcarine sulcus (V1). Functional alteration in the calcarine differs along its length, reflecting center to periphery visual space differences. Herein, we aim to connect between these two sets of findings by looking at the retinotopic patterns of functional connectivity between large-scale brain networks and V1, comparing patients with normally sighted subjects.
Resting state functional magnetic resonance imaging (fMRI) and T1 anatomical scans were obtained from 11 PCA patients and 17 age-matched healthy volunteers. Default mode network (DMN) and fronto parietal network (FPN) were defined and differences between the networks in patients and healthy controls were evaluated at the whole brain level, specifically their connectivity to V1.
Connectivity patterns within the DMN and the FPN were similar between the groups, although differences were found in regions within and beyond the networks. Focusing on V1, in the control group we identified the expected pattern of a distributed connectivity along eccentricity, with foveal regions showing stronger connectivity to the FPN and peripheral regions showing stronger connectivity to the DMN. However, in PCA patients we could not identify a clear difference in connectivity along the eccentricities.
Lost specialization of function along the calcarine in PCA patients may have further implications on large-scale networks or vice versa. This impairment, distant from the core pathology, might explain patients' visual disabilities.
后部皮质萎缩（PCA）是阿尔茨海默病的一种视觉变异，最初表现为高级视觉障碍和顶颞枕叶萎缩。最近的研究表明，在远距离脑网络和距状沟（V1）沿线都存在远程功能障碍。V1 沿其长度的功能改变不同，反映了中心到外周视觉空间的差异。在此，我们旨在通过观察大尺度脑网络与 V1 之间功能连接的视网膜空间模式，将这两组发现联系起来，比较 PCA 患者与视力正常的受试者。
从 11 名 PCA 患者和 17 名年龄匹配的健康志愿者中获得静息状态功能磁共振成像（fMRI）和 T1 解剖扫描。定义默认模式网络（DMN）和额顶网络（FPN），并在全脑水平评估网络在患者和健康对照组之间的差异，特别是它们与 V1 的连接。
两组之间 DMN 和 FPN 内的连接模式相似，但在网络内和网络外的区域存在差异。关注 V1，在对照组中，我们发现了沿着离焦分布的连接的预期模式，中央区域与 FPN 的连接更强，周边区域与 DMN 的连接更强。然而，在 PCA 患者中，我们无法沿着离焦确定连接的明显差异。
PCA 患者距状沟功能的丧失可能对大尺度网络有进一步的影响，反之亦然。这种远离核心病理的损害可能解释了患者的视觉障碍。
