Single-tensor diffusion imaging (DTI) has traditionally been used to assess integrity of white matter. For example, we previously showed that integrity of limbic white matter tracts declines in healthy aging and relates to episodic memory performance. However, multi-compartment diffusion models may be more informative about microstructural properties of gray matter. The current study examined hippocampal gray matter integrity using both single-tensor and multi-compartment (neurite orientation dispersion and density imaging, NODDI) diffusion imaging. Younger (20-38 years) and older (59-84 years) adults also completed the Mnemonic Similarity Task to measure mnemonic discrimination performance. Results revealed age-related declines in both single-tensor (lower fractional anisotropy, higher mean diffusivity) and multi-compartment (higher restricted, hindered and free diffusion) measures of hippocampal gray matter integrity. As expected, NODDI measures (hindered and free diffusion) captured more age-related variance than DTI measures. Moreover, mnemonic discrimination of highly similar lure items in memory was related to hippocampal gray matter integrity in younger but not older adults. These findings support the notion that age-related differences in gray matter integrity are better captured by multi-compartment versus single-tensor diffusion models and show that the relationship between mnemonic discrimination and hippocampal gray matter integrity is moderated by age.

中文翻译：

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与单张量扩散成像相比，NODDI 可以更好地捕获海马灰质完整性中与年龄和记忆相关的差异


单张量扩散成像（DTI）传统上用于评估白质的完整性。例如，我们之前表明，边缘白质束的完整性在健康衰老过程中会下降，并且与情景记忆表现有关。然而，多室扩散模型可能提供更多有关灰质微观结构特性的信息。当前的研究使用单张量和多室（神经突定向弥散和密度成像，NODDI）扩散成像检查海马灰质完整性。较年轻（20-38 岁）和较年长（59-84 岁）的成年人也完成了助记符相似性任务，以衡量助记符辨别表现。结果显示，海马灰质完整性的单张量（分数各向异性较低，平均扩散率较高）和多室（较高的受限、受阻和自由扩散）测量值均出现与年龄相关的下降。正如预期的那样，NODDI 测量（受阻扩散和自由扩散）比 DTI 测量捕获了更多与年龄相关的方差。此外，记忆中高度相似的诱饵项目的记忆辨别与年轻人的海马灰质完整性有关，但与老年人无关。这些发现支持这样的观点，即与单张量扩散模型相比，多室扩散模型可以更好地捕获与年龄相关的灰质完整性差异，并表明助记辨别力和海马灰质完整性之间的关系受到年龄的调节。