The status of the precommissural and postcommissural fornix in normal ageing and mild cognitive impairment: An MRI tractography study.
The status of the precommissural and postcommissural fornix in normal ageing and mild cognitive impairment: An MRI tractography study.
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DOI：
10.1016/j.neuroimage.2015.12.055
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发表时间：
2016-04-15
期刊：
影响因子：
5.7
通讯作者：
Metzler-Baddeley C
中科院分区：
文献类型：
--
作者：
Christiansen K;Aggleton JP;Parker GD;O'Sullivan MJ;Vann SD;Metzler-Baddeley C
穹窿连接海马结构和颞叶以外的结构。以前的纤维束成像研究通常将穹窿重建为一个统一的束。然而，穹窿包含两个吻部：前连合穹窿和后连合穹窿。每个分区都有不同的解剖学连接，因此可能有不同的功能。采用弥散加权MRI和基于球面去卷积的纤维束成像重建这些单独的穹窿分区，并检查健康老龄化和轻度认知障碍（MCI）患者的微结构特性。两组均实现了可靠的前连合和后连合纤维重建，其纤维在穹窿前体内保留了很大程度上独立的位置。老龄化和MCI对这两个部分的影响相当。老化与平均值，轴向和径向扩散率的变化，但不与改变纤维人口特定的扩散性能，估计与阻碍调制取向各向异性（HMOA）。个体HMOA变异后连合，但不precommissural，纤维呈正相关（与年龄无关）与视觉回忆性能。这提供了新的证据的作用后连合纤维，连接结构的扩展海马网络，情节记忆功能。将穹窿分为两个主要部分为区分不同的海马网络带来了新的机会。穹窿有两个吻侧分区，具有不同的解剖学连接分离连合前和连合后穹窿的新纤维束成像方案连合后HMOA和情景记忆之间的正相关性，扩散率增加，但穹窿的HMOA不增加轻度认知障碍影响两个分区的微结构
The fornix connects the hippocampal formation with structures beyond the temporal lobe. Previous tractography studies have typically reconstructed the fornix as one unified bundle. However, the fornix contains two rostral divisions: the precommissural fornix and the postcommissural fornix. Each division has distinct anatomical connections and, hence, potentially distinct functions. Diffusion weighted MRI and spherical deconvolution based tractography were employed to reconstruct these separate fornix divisions and to examine their microstructural properties in both healthy ageing and Mild Cognitive Impairment (MCI). Reliable reconstructions of precommissural and postcommissural fibres were achieved in both groups, with their fibres retaining largely separate locations within the anterior body of the fornix. Ageing and MCI had comparable effects on the two segments. Ageing was associated with changes in mean, axial and radial diffusivity but not with alterations of fibre population-specific diffusion properties, estimated with the hindrance modulated orientational anisotropy (HMOA). Individual HMOA variation in postcommissural, but not precommissural, fibres correlated positively (and unrelated to age) with visual recall performance. This provides novel evidence for a role of postcommissural fibres, which connect structures of the extended hippocampal network, in episodic memory function. Separating the fornix into its two principal divisions brings new opportunities for distinguishing different hippocampal networks. Fornix has two rostral divisions with distinct anatomical connections New tractography protocol for separating precommissural and postcommissural fornix Positive correlation between postcommissural HMOA and episodic memory Age-related increases in diffusivity but not in HMOA of fornix Mild Cognitive Impairment affects microstructure in both divisions