Experiments on rodents have demonstrated that transecting the white matter fibre pathway linking the hippocampus with an array of cortical and subcortical structures - the fornix - impairs flexible navigational learning in the Morris Water Maze (MWM), as well as similar spatial learning tasks. While diffusion magnetic resonance imaging (dMRI) studies in humans have linked inter-individual differences in fornix microstructure to episodic memory abilities, its role in human spatial learning is currently unknown. We used high-angular resolution diffusion MRI combined with constrained spherical deconvolution-based tractography, to ask whether inter-individual differences in fornix microstructure in healthy young adults would be associated with spatial learning in a virtual reality navigation task. To efficiently capture individual learning across trials, we adopted a novel curve fitting approach to estimate a single index of learning rate. We found a statistically significant correlation between learning rate and the microstructure (mean diffusivity) of the fornix, but not that of a comparison tract linking occipital and anterior temporal cortices (the inferior longitudinal fasciculus, ILF). Further, this correlation remained significant when controlling for both hippocampal volume and participant gender. These findings extend previous animal studies by demonstrating the functional relevance of the fornix for human spatial learning in a virtual reality environment, and highlight the importance of a distributed neuroanatomical network, underpinned by key white matter pathways, such as the fornix, in complex spatial behaviour.

中文翻译：

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穹窿在人类导航学习中的作用。


对啮齿动物的实验表明，横断连接海马体与一系列皮质和皮质下结构（穹窿）的白质纤维通路会损害莫里斯水迷宫（MWM）中的灵活导航学习以及类似的空间学习任务。虽然人类扩散磁共振成像（dMRI）研究已将穹窿微观结构的个体差异与情景记忆能力联系起来，但其在人类空间学习中的作用目前尚不清楚。我们使用高角分辨率扩散 MRI 与基于约束球面解卷积的纤维束成像技术相结合，探讨健康年轻人穹窿微结构的个体间差异是否与虚拟现实导航任务中的空间学习相关。为了有效地捕获试验中的个体学习，我们采用了一种新颖的曲线拟合方法来估计单个学习率指数。我们发现学习率和穹窿的微观结构（平均扩散率）之间存在统计上显着的相关性，但与连接枕叶和前颞皮质（下纵束，ILF）的比较束之间没有相关性。此外，当控制海马体积和参与者性别时，这种相关性仍然显着。这些发现扩展了先前的动物研究，证明了穹窿与虚拟现实环境中人类空间学习的功能相关性，并强调了以穹窿等关键白质通路为基础的分布式神经解剖网络在复杂空间行为中的重要性。