Department of Psychology, University of Notre Dame, Notre Dame, Indiana 46556,
Center for Vital Longevity, University of Texas at Dallas, Dallas, Texas 75235.
J Neurosci. 2019 Jan 2;39(1):149-162. doi: 10.1523/JNEUROSCI.1498-18.2018. Epub 2018 Nov 2.
Healthy aging is associated with decreased neural selectivity (dedifferentiation) in category-selective cortical regions. This finding has prompted the suggestion that dedifferentiation contributes to age-related cognitive decline. Consistent with this possibility, dedifferentiation has been reported to negatively correlate with fluid intelligence in older adults. Here, we examined whether dedifferentiation is associated with performance in another cognitive domain-episodic memory-that is also highly vulnerable to aging. Given the proposed role of dedifferentiation in age-related cognitive decline, we predicted there would be a stronger link between dedifferentiation and episodic memory performance in older than in younger adults. Young (18-30 years) and older (64-75 years) male and female humans underwent fMRI scanning while viewing images of objects and scenes before a subsequent recognition memory test. We computed a differentiation index in two regions of interest (ROIs): parahippocampal place area (PPA) and lateral occipital complex (LOC). This index quantified the selectivity of the BOLD response to preferred versus nonpreferred category of an ROI (scenes for PPA, objects for LOC). The differentiation index in the PPA, but not the LOC, was lower in older than in younger adults. Additionally, the PPA differentiation index predicted recognition memory performance for the studied items. This relationship was independent of and not moderated by age. The PPA differentiation index also predicted performance on a latent "fluency" factor derived from a neuropsychological test battery; this relationship was also age invariant. These findings suggest that two independent factors, one associated with age, and the other with cognitive performance, influence neural differentiation. Aging is associated with neural dedifferentiation-reduced neural selectivity in "category-selective" cortical brain regions-which has been proposed to contribute to cognitive aging. Here, we examined whether neural differentiation is predictive of episodic memory performance, and whether the relationship is moderated by age. A neural differentiation index was estimated for scene-selective (PPA) and object-selective (LOC) cortical regions while participants studied images for a subsequent memory test. Age-related reductions were observed for the PPA, but not for the LOC, differentiation index. Importantly, the PPA differentiation index demonstrated age-invariant correlations with subsequent memory performance and a fluency factor derived from a neuropsychological battery. Together, these findings suggest that neural differentiation is associated with two independent factors: age and cognitive performance.
健康的衰老与类别选择性皮质区域的神经选择性降低（去分化）有关。这一发现促使人们提出去分化有助于与年龄相关的认知能力下降。与这种可能性一致，去分化已被报道与老年人的流体智力呈负相关。在这里，我们研究了去分化是否与另一个认知领域——情景记忆——的表现有关，情景记忆也非常容易受到衰老的影响。鉴于去分化在与年龄相关的认知能力下降中的作用，我们预测去分化与老年人情景记忆表现之间的联系比年轻人更强。年轻（18-30 岁）和年长（64-75 岁）的男性和女性在观看物体和场景的图像后，进行 fMRI 扫描，然后进行后续的识别记忆测试。我们在两个感兴趣的区域（ROI）计算了分化指数：海马旁回位置区（PPA）和外侧枕叶复合体（LOC）。该指数量化了 ROI 中对首选与非首选类别的 BOLD 反应的选择性（PPA 为场景，LOC 为物体）。与年轻人相比，老年人的 PPA 分化指数较低。此外，PPA 的分化指数预测了对所研究项目的识别记忆表现。这种关系独立于年龄，不受年龄调节。PPA 的分化指数还预测了神经心理测试组合中得出的潜在“流畅性”因素的表现；这种关系也与年龄无关。这些发现表明，两个独立的因素，一个与年龄有关，另一个与认知表现有关，影响神经分化。衰老与神经去分化有关，即“类别选择性”皮质大脑区域的神经选择性降低，这被认为是认知衰老的原因。在这里，我们研究了神经分化是否可以预测情景记忆表现，以及这种关系是否受年龄调节。在参与者为后续记忆测试学习图像时，估计了场景选择性（PPA）和物体选择性（LOC）皮质区域的神经分化指数。与年轻人相比，PPA 的分化指数呈年龄相关的下降，但 LOC 的分化指数没有下降。重要的是，PPA 的分化指数与随后的记忆表现和神经心理测试组合中得出的流畅性因素呈年龄不变的相关性。综上所述，神经分化与两个独立的因素有关：年龄和认知表现。
