Center for Lifespan Changes in Brain and Cognition, University of Oslo, Norway.
Department of Radiology and Nuclear Medicine, Oslo University Hospital, Oslo, Norway.
Hippocampus. 2020 Jul;30(7):678-692. doi: 10.1002/hipo.23189. Epub 2020 Jan 21.
There is evidence for a hippocampal long axis anterior-posterior (AP) differentiation in memory processing, which may have implications for the changes in episodic memory performance seen across development and aging. The hippocampus shows substantial structural changes with age, but the lifespan trajectories of hippocampal sub-regions along the AP axis are not established. The aim of the present study was to test whether the micro- and macro-structural age-trajectories of the anterior (aHC) and posterior (pHC) hippocampus are different. In a single-center longitudinal study, 1,790 cognitively healthy participants, 4.1-93.4 years of age, underwent a total of 3,367 MRI examinations and 3,033 memory tests sessions over 1-6 time points, spanning an interval up to 11.1 years. T1-weighted scans were used to estimate the volume of aHC and pHC (macrostructure), and diffusion tensor imaging to measure mean diffusion (MD, microstructure) within each region. We found that the macro- and microstructural lifespan-trajectories of aHC and pHC were clearly distinguishable, with partly common and partly unique variance shared with age. aHC showed a protracted period of microstructural development, while pHC microstructural development as indexed by MD was more or less completed in early childhood. In contrast, pHC showed larger unique aging-related changes. An aHC-pHC difference was also observed for volume, with pHC changing relatively more with higher age. All regions showed age-dependent relationships with episodic memory. aHC micro- and macrostructure was significantly related to verbal memory independently of age, but the relationships were still strongest among the older participants. We suggest that memory processes supported by each sub-region improve or decline in concert with volumetric and microstructural changes in the same age-period. Future research should disentangle the lifespan relationship between changes in these structural properties and different memory processes, encoding versus retrieval in particular, as well as other cognitive functions depending on the hippocampal long-axis specialization.
有证据表明，在记忆处理过程中，海马体具有长轴从前到后的（AP）分化，这可能对整个发育和衰老过程中观察到的情景记忆表现的变化产生影响。随着年龄的增长，海马体发生了大量的结构变化，但沿着 AP 轴的海马体亚区的寿命轨迹尚未确定。本研究的目的是测试前（aHC）和后（pHC）海马体的微观和宏观结构的年龄轨迹是否不同。在一项单中心纵向研究中，1790 名认知健康的参与者，年龄在 4.1-93.4 岁之间，在 1-6 个时间点进行了总共 3367 次 MRI 检查和 3033 次记忆测试，间隔长达 11.1 年。T1 加权扫描用于估计 aHC 和 pHC 的体积（宏观结构），并使用弥散张量成像测量每个区域内的平均弥散（MD，微观结构）。我们发现，aHC 和 pHC 的宏观和微观结构的寿命轨迹是明显可区分的，与年龄共享部分共同和部分独特的方差。aHC 表现出微观结构发育的延长时期，而 pHC 微观结构的发展，如 MD 所表示的，在儿童早期基本完成。相比之下，pHC 显示出更大的与年龄相关的独特变化。在体积方面也观察到 aHC-pHC 差异，随着年龄的增长，pH 变化相对更大。所有区域的记忆表现都与情景记忆呈年龄依赖性关系。aHC 的微观和宏观结构与年龄独立相关，与语言记忆显著相关，但在年龄较大的参与者中，这种关系仍然最强。我们认为，每个亚区支持的记忆过程随着同一时期的体积和微观结构变化而改善或下降。未来的研究应该厘清这些结构特性的变化与不同记忆过程（特别是编码与检索）以及其他认知功能之间的寿命关系，这取决于海马体长轴的专业化。
