ABSTRACT

According to the neural dedifferentiation hypothesis, age-related reductions in the distinctiveness of neural representations contribute to sensory, cognitive, and motor declines associated with aging: neural activity associated with different stimulus categories becomes more confusable with age and behavioral performance suffers as a result. Initial studies investigated age-related dedifferentiation in the visual cortex, but subsequent research has revealed declines in other brain regions, suggesting that dedifferentiation may be a general feature of the aging brain. In the present study, we used functional magnetic resonance imaging to investigate age-related dedifferentiation in the visual, auditory, and motor cortices. Participants were 58 young adults and 79 older adults. The similarity of activation patterns across different blocks of the same category was calculated (within-category correlation, a measure of reliability) as was the similarity of activation patterns elicited by different categories (between-category correlations, a measure of confusability). Neural distinctiveness was defined as the difference between the mean within- and between-category similarity. We found age-related reductions in neural distinctiveness in the visual, auditory, and motor cortices, which were driven by both decreases in within-category similarity and increases in between-category similarity. There were significant positive cross-region correlations between neural distinctiveness in different regions. These correlations were driven by within-category similarities, a finding that indicates that declines in the reliability of neural activity appear to occur in tandem across the brain. These findings suggest that the changes in neural distinctiveness that occur in healthy aging result from changes in both the reliability and confusability of patterns of neural activity.

摘要

根据神经去分化假说，与年龄相关的神经表征的独特性降低会导致与衰老相关的感觉、认知和运动能力下降：与不同刺激类别相关的神经活动随着年龄的增长而变得更加容易混淆，从而导致行为表现受到影响。最初的研究调查了视觉皮层中与年龄相关的去分化，但随后的研究显示其他大脑区域的衰退，这表明去分化可能是大脑衰老的一个普遍特征。在本研究中，我们使用功能性磁共振成像来研究视觉、听觉和运动皮层与年龄相关的去分化。参与者是 58 名年轻人和 79 名老年人。计算了同一类别的不同块之间激活模式的相似性（类别内相关性，可靠性的度量），以及不同类别引发的激活模式的相似性（类别间相关性，混淆性的度量）。神经独特性被定义为类别内和类别间的平均相似性之间的差异。我们发现与年龄相关的视觉、听觉和运动皮层的神经独特性降低，这是由于类别内相似性降低和类别间相似性增加所致。不同区域的神经独特性之间存在显着的跨区域正相关。这些相关性是由类别内的相似性驱动的，这一发现表明，神经活动可靠性的下降似乎在整个大脑中同时发生。这些发现表明，健康老龄化过程中发生的神经独特性变化是由神经活动模式的可靠性和易混淆性的变化引起的。