The hippocampus is a brain structure that plays key roles in a variety of cognitive processes. Critically, a wide range of neurological disorders are associated with degeneration of the hippocampal microstructure, defined as neurons, dendrites, glial cells, and more. Thus, the hippocampus is a key target for methods that are sensitive to these microscale properties. Diffusion MRI is one such method, which can noninvasively probe neural architecture. Here we review the extensive use of diffusion MRI to capture hippocampal microstructure in both health and disease. The results of these studies indicate that (1) diffusion tensor imaging is sensitive but not specific to the hippocampal microstructure; (2) biophysical modeling of diffusion MRI signals is a promising avenue to capture more specific aspects of the hippocampal microstructure; (3) use of ultra-short diffusion times have shown unique laminar-specific microstructure and response to hippocampal injury; (4) dispersion of microstructure is likely abundant in the hippocampus; and (5) the angular richness of the diffusion MRI signal can be leveraged to improve delineation of the internal hippocampal circuitry. Overall, extant findings suggest that diffusion MRI offers a promising avenue for characterizing hippocampal microstructure.

海马体是一种大脑结构，在各种认知过程中发挥着关键作用。重要的是，多种神经系统疾病都与海马微观结构（定义为神经元、树突、神经胶质细胞等）的退化有关。因此，海马体是对这些微观特性敏感的方法的关键目标。扩散磁共振成像就是这样一种方法，它可以无创地探测神经结构。在这里，我们回顾了扩散磁共振成像在健康和疾病中捕获海马微观结构的广泛应用。这些研究结果表明：（1）扩散张量成像对海马微观结构敏感但不具有特异性； (2) 扩散 MRI 信号的生物物理建模是捕获海马微结构更具体方面的有前途的途径； (3)利用超短扩散时间显示出独特的层状特异性微观结构和对海马损伤的反应； (4)海马体内微结构的分散性可能很丰富； (5) 可以利用扩散 MRI 信号的角度丰富度来改善海马内部电路的描绘。总体而言，现有研究结果表明，扩散 MRI 为表征海马微观结构提供了一种有前景的途径。