Evidence from animal and histological studies has indicated that accumulation of iron in the brain results in reactive gliosis that contributes to cognitive deficits. The current study extends these findings to human cognitive aging and suggests that magnetic resonance imaging (MRI) techniques like quantitative relaxometry can be used to study iron and its effects in vivo. The effects of iron on microstructure and memory performance were examined using a combination of quantitative relaxometry and multicompartment diffusion imaging in 35 young (21.06 ± 2.18 years) and 28 older (72.58 ± 6.47 years) adults, who also completed a memory task. Replicating past work, results revealed age-related increases in iron content (R2*) and diffusion, and decreases in memory performance. Independent of age group, iron content was significantly related to restricted (intracellular) diffusion in regions with low-moderate iron (hippocampus, caudate) and to all diffusion metrics in regions with moderate-high iron (putamen, globus pallidus). This pattern is consistent with different stages of iron-related gliosis, ranging from astrogliosis that may influence intracellular diffusion to microglial proliferation and increased vascular permeability that may influence all sources of diffusion. Further, hippocampal restricted diffusion was significantly related to memory performance, with a third of this effect related to iron content; consistent with the hypothesis that higher iron-related astrogliosis in the hippocampus is associated with poorer memory performance. These results demonstrate the sensitivity of MRI to iron-related gliosis and extend our understanding of its impact on cognition by showing that this relationship also explains individual differences in memory performance.

中文翻译：

---

铁和神经胶质增生的神经影像学测量解释了衰老中的记忆表现

动物和组织学研究的证据表明，铁在大脑中的积累会导致反应性神经胶质增生，从而导致认知缺陷。目前的研究将这些发现扩展到人类认知老化，并表明磁共振成像 (MRI) 技术（如定量弛豫测量法）可用于研究铁及其在体内的影响。在 35 名年轻（​​21.06 ± 2.18 岁）和 28 名老年人（72.58 ± 6.47 岁）成年人中，使用定量弛豫测量法和多室扩散成像相结合，检查了铁对微观结构和记忆性能的影响，他们也完成了一项记忆任务。复制过去的工作，结果显示与年龄相关的铁含量（R2*）和扩散增加，以及记忆力下降。不分年龄组，铁含量与中低铁区域（海马、尾状核）的受限（细胞内）扩散和中高铁区域（壳核、苍白球）的所有扩散指标显着相关。这种模式与铁相关神经胶质增生的不同阶段一致，从可能影响细胞内扩散的星形胶质细胞增生到可能影响所有扩散来源的小胶质细胞增殖和血管通透性增加。此外，海马受限扩散与记忆能力显着相关，其中三分之一与铁含量有关；与海马中较高的铁相关星形胶质细胞增生与较差的记忆表现相关的假设一致。