With an increasing prevalence of mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in response to an aging population, it is critical to identify and understand neuroprotective mechanisms against cognitive decline. One potential mechanism is redundancy: the existence of duplicate elements within a system that provide alternative functionality in case of failure. As the hippocampus is one of the earliest sites affected by AD pathology, we hypothesized that functional hippocampal redundancy is protective against cognitive decline. We compared hippocampal functional redundancy derived from resting-state functional MRI networks in cognitively normal older adults, with individuals with early and late MCI, as well as the relationship between redundancy and cognition. Posterior hippocampal redundancy was reduced between cognitively normal and MCI groups, plateauing across early and late MCI. Higher hippocampal redundancy was related to better memory performance only for cognitively normal individuals. Critically, functional hippocampal redundancy did not come at the expense of network efficiency. Our results provide support that hippocampal redundancy protects against cognitive decline in aging.

随着人口老龄化导致轻度认知障碍（MCI）和阿尔茨海默病（AD）的患病率不断增加，识别和了解对抗认知能力下降的神经保护机制至关重要。一种潜在的机制是冗余：系统中存在重复的元素，在发生故障时提供替代功能。由于海马体是最早受 AD 病理影响的部位之一，我们假设功能性海马体冗余可以防止认知能力下降。我们比较了认知正常老年人、早期和晚期 MCI 个体的静息态功能 MRI 网络衍生的海马功能冗余，以及冗余与认知之间的关系。认知正常组和 MCI 组之间后海马冗余减少，在早期和晚期 MCI 中趋于稳定。仅对于认知正常的个体来说，较高的海马冗余度与更好的记忆表现有关。至关重要的是，功能性海马冗余并不是以牺牲网络效率为代价的。我们的研究结果支持海马冗余可以防止衰老过程中的认知能力下降。