Emerging studies have emphasized the importance of the fidelity of cortical representation in forming enduring episodic memory. No study, however, has examined whether there are age-related reductions in representation fidelity that can explain memory declines in normal aging. Using functional MRI and multivariate pattern analysis, we found that older adults showed reduced representation fidelity in the visual cortex, which accounted for their decreased memory performance even after controlling for the contribution of reduced activation level. This reduced fidelity was specifically due to older adults' poorer item-specific representation, not due to their lower activation level and variance, greater variability in neuro-vascular coupling, or decreased selectivity of categorical representation (i.e., dedifferentiation). Older adults also showed an enhanced subsequent memory effect in the prefrontal cortex based on activation level, and their prefrontal activation was associated with greater fidelity of representation in the visual cortex and better memory performance. The fidelity of cortical representation thus may serve as a promising neural index for better mechanistic understanding of the memory declines and its compensation in normal aging.

译文

新兴研究强调了皮质表示的保真度在形成持久的情景记忆中的重要性。然而,没有研究检查是否存在与年龄相关的代表保真度降低,可以解释正常衰老时的记忆力下降。使用功能MRI和多变量模式分析,我们发现老年人在视觉皮层中的表现保真度降低,即使在控制了激活水平降低的贡献后,他们的记忆表现也会降低。保真度的降低是特别由于老年人的项目特异性表现较差,而不是由于其激活水平和差异较低,神经-血管偶联的变异性较大或分类表现的选择性降低 (即去分化)。老年人还显示出基于激活水平的前额叶皮层增强的后续记忆效应,并且他们的前额叶激活与视觉皮层中更大的表现保真度和更好的记忆性能相关。因此,皮质表示的保真度可以作为一种有前途的神经指标,以更好地从机械上理解记忆力下降及其在正常衰老中的补偿。

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