Neuropsychological and functional magnetic resonance imaging (MRI) evidence suggests that the ability to vividly remember our personal past, and imagine future scenarios, involves two closely connected regions: the hippocampus and ventromedial prefrontal cortex (vmPFC). Despite evidence of a direct anatomical connection from hippocampus to vmPFC, it is unknown whether hippocampal-vmPFC structural connectivity supports both past and future-oriented episodic thinking. To address this, we applied diffusion-weighted magnetic resonance imaging (dMRI) and a novel deterministic tractography protocol to reconstruct distinct subdivisions of the fornix previously detected in axonal tracer studies, namely pre-commissural (connecting the hippocampus to vmPFC) and post-commissural (linking the hippocampus and medial diencephalon) fornix, in a group of healthy young adult humans who undertook an adapted past-future autobiographical interview (portions of this data were published in Hodgetts et al., 2017). As predicted, we found that inter-individual differences in pre-commissural - but not post-commissural - fornix microstructure (fractional anisotropy) were significantly correlated with the episodic richness of both past and future autobiographical narratives. Notably, these results remained significant when controlling for non-episodic narrative content, verbal fluency, and grey matter volumes of the hippocampus and vmPFC. This study provides novel evidence that reconstructing events from one's personal past, and constructing possible future events, involves a distinct, structurally-instantiated hippocampal-vmPFC pathway.

神经心理学和功能性磁共振成像 (MRI) 证据表明，生动地记住个人过去和想象未来情景的能力涉及两个紧密相连的区域：海马体和腹内侧前额叶皮层 (vmPFC)。尽管有证据表明海马与 vmPFC 之间存在直接的解剖学联系，但海马-vmPFC 结构连接是否支持过去和面向未来的情景思维尚不清楚。为了解决这个问题，我们应用扩散加权磁共振成像（dMRI）和一种新颖的确定性纤维束成像方案来重建先前在轴突示踪剂研究中检测到的穹窿的不同细分，即前连合（将海马体连接到 vmPFC）和后连合（连接海马体和内侧间脑）穹窿，在一组健康的年轻成年人中，他们进行了改编的过去未来自传式访谈（部分数据发表在 Hodgetts 等人，2017 年）。正如预测的那样，我们发现连合前（而非连合后）穹窿微结构（分数各向异性）的个体间差异与过去和未来自传叙事的情节丰富度显着相关。值得注意的是，在控制非情景叙事内容、语言流畅性以及海马体和 vmPFC 的灰质体积时，这些结果仍然很显着。这项研究提供了新的证据，表明从一个人的个人过去重建事件并构建未来可能的事件涉及一个独特的、结构实例化的海马-vmPFC 通路。