The social cost of iron: brain iron in face-processing regions links lower face-perception performance to reduced social connectedness in aging.

Face perception is fundamental to social interaction yet declines in older individuals. The social implications and mechanisms of this decline remain unclear. Here, we tested whether face-perception performance of 35 healthy, older adults is related to social connectedness and assessed regional brain iron as a hypothetical underlying mechanism. Face and non-face perception was assessed with the Cambridge Face and Cambridge Car Memory Test. Social connectedness was indexed as a composite of the Duke Social Support Index, UCLA Loneliness Scale, and Lubben Social Network Scale. A discrimination task to localize face- and house- processing was completed with fMRI data acquisition, and quantitative susceptibility mapping to index brain iron load was collected. Iron load in face-processing regions—but not in control regions—was associated with poorer face, but not non-face, perception, and poorer face-perception was also associated with lower social connectedness. Mediation analyses supported a perceptual-social pathway in aging whereby regional brain iron relates to lower social connectedness via face perception.

面部感知（face perception）是社会互动的核心基础，然而老年个体的面部感知能力会出现衰退。目前此类衰退的社会影响与潜在机制仍不明确。本研究纳入35名健康老年个体，测试其面部感知表现与社会联结程度的相关性，并以脑区铁含量作为假说中的潜在机制开展评估。研究采用剑桥面部记忆测试（Cambridge Face Memory Test）与剑桥车辆记忆测试（Cambridge Car Memory Test），分别评估面部感知与非面部感知能力。社会联结程度以杜克社会支持量表（Duke Social Support Index）、加州大学洛杉矶分校孤独感量表（UCLA Loneliness Scale）及鲁本社交网络量表（Lubben Social Network Scale）的综合得分作为量化指标。研究通过功能磁共振成像（fMRI）采集数据，完成定位面部与房屋加工的辨别任务，并通过定量磁化率成像（quantitative susceptibility mapping）量化脑内铁负荷水平。结果显示，面部加工脑区的铁负荷（而非对照脑区）与更差的面部感知能力相关，而与非面部感知能力无关联；同时，较差的面部感知能力也与更低的社会联结程度相关。中介分析验证了衰老过程中的感知-社会通路：脑区铁含量通过影响面部感知能力，进而与更低的社会联结程度相关联。