Structural integrity of the human hippocampus is widely acknowledged to be necessary for the successful encoding and retrieval of autobiographical memories. However, evidence for an association between hippocampal volume and the ability to recall such memories in healthy individuals is mixed. Here we examined this issue further by combining two approaches. First, we focused on the anatomically distinct subregions of the hippocampus where more nuanced associations may be expressed compared to considering the whole hippocampal volume. A manual segmentation protocol of hippocampal subregions allowed us to separately calculate the volumes of the dentate gyrus/CA4, CA3/2, CA1, subiculum, pre/parasubiculum and uncus. Second, a critical feature of autobiographical memories is that they can span long time periods, and so we sought to consider how memory details persist over time by conducting a longitudinal study whereby participants had to recall the same autobiographical memories on two visits spaced 8 months apart. Overall, we found that there was no difference in the total number of internal (episodic) details produced at Visits 1 and 2. However, further probing of detail subcategories revealed that specifically the amount of subjective thoughts and emotions included during recall had declined significantly by the second visit. We also observed a strong correlation between left pre/parasubiculum volume and the amount of autobiographical memory internal details produced over time. This positive relationship was evident for particular facets of the memories, with remembered events, perceptual observations and thoughts and emotions benefitting from greater volume of the left pre/parasubiculum. These preliminary findings expand upon existing functional neuroimaging evidence by highlighting a potential link between left pre/parasubiculum volume and autobiographical memory. A larger pre/parasubiculum appears not only to protect against memory decay, but may possibly enhance memory persistence, inviting further scrutiny of the role of this brain region in remote autobiographical memory retrieval.

中文翻译：

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海马亚区体积与自传体记忆持久性的关系

人类海马体的结构完整性被广泛认为是成功编码和检索自传记忆所必需的。然而，海马体积与健康个体回忆此类记忆的能力之间存在关联的证据好坏参半。在这里，我们通过结合两种方法进一步研究了这个问题。首先，我们专注于海马体解剖学上不同的亚区，与考虑整个海马体体积相比，这些亚区可能表达更细微的关联。海马亚区的手动分割协议使我们能够分别计算齿状回/CA4、CA3/2、CA1、下托、前/副下托和钩部的体积。其次，自传式记忆的一个关键特征是它们可以跨越很长的时间段，因此，我们试图通过进行一项纵向研究来考虑记忆细节如何随着时间的推移而持续存在，参与者必须在相隔 8 个月的两次访问中回忆相同的自传记忆。总体而言，我们发现在访问 1 和 2 中产生的内部（情节）细节的总数没有差异。但是，对细节子类别的进一步探索显示，特别是回忆期间包含的主观思想和情绪的数量显着下降了第二次访问。我们还观察到左前/副下颌骨体积与随时间产生的自传记忆内部细节的数量之间存在很强的相关性。这种积极的关系在记忆的特定方面很明显，记忆中的事件，感知观察、思想和情绪受益于更大的左侧前/副下颌骨。这些初步发现通过突出左侧前/副下颌骨体积与自传体记忆之间的潜在联系，扩展了现有的功能性神经影像学证据。更大的前/副下骨似乎不仅可以防止记忆衰退，而且可能会增强记忆持久性，从而进一步审查该大脑区域在远程自传记忆检索中的作用。