Although hippocampal volume has served as a long-standing predictor of cognitive decline, diffusion magnetic resonance imaging studies of white matter have shown similar relationships. Still, it remains unclear if gray matter and white matter interact to predict cognitive impairment and longitudinal decline. Here, we investigate whether free-water (FW) and FW-corrected fractional anisotropy (FAT) within medial temporal lobe white matter tracts provides meaningful contribution to cognition and cognitive decline beyond hippocampal volume. Using data from the Vanderbilt Memory & Aging Project (n = 319), we found that FW was associated with baseline memory and executive function beyond that of hippocampal volume and other comorbidities. Longitudinal analyses demonstrated significant interactions of hippocampal volume and inferior longitudinal fasciculus (p = 0.043) and cingulum bundle (p = 0.025) FAT on memory decline and with fornix FAT (p = 0.025) on decline in executive function. Results suggest that FW metrics of white matter have a unique role in cognitive decline and should be included in theoretical models of aging, cerebrovascular disease, and Alzheimer's disease.

中文翻译：

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内侧颞叶白质束预测中的自由水指标与纵向认知衰退有关

尽管海马体积一直是认知能力下降的一个长期预测指标，但对白质的弥散磁共振成像研究显示出类似的关系。尽管如此，灰质和白质是否相互作用以预测认知障碍和纵向衰退仍不清楚。在这里，我们调查内侧颞叶白质束内的游离水 (FW) 和 FW 校正分数各向异性 (FAT) 是否对海马体积以外的认知和认知能力下降提供了有意义的贡献。使用 Vanderbilt Memory & Aging Project (n = 319) 的数据，我们发现 FW 与基线记忆和执行功能相关，超出了海马体积和其他合并症。纵向分析表明，海马体积和下纵束 (p = 0.043) 和扣带束 (p = 0.025) FAT 之间存在显着的相互作用，记忆力下降，穹窿 FAT (p = 0.025) 与执行功能下降有关。结果表明，白质的 FW 指标在认知能力下降中具有独特的作用，应包括在衰老、脑血管疾病和阿尔茨海默病的理论模型中。