Aging is accompanied by a decline of working memory, an important cognitive capacity that involves stimulus-selective neural activity that persists after stimulus presentation. Here, we unraveled working memory dynamics in older human adults (male and female) including those diagnosed with mild cognitive impairment (MCI) using a combination of behavioral modeling, neuropsychological assessment, and MEG recordings of brain activity. Younger adults (male and female) were studied with behavioral modeling only. Participants performed a visuospatial delayed match-to-sample task under systematic manipulation of the delay and distance between sample and test stimuli. Their behavior (match/nonmatch decisions) was fit with a computational model permitting the dissociation of noise in the internal operations underlying the working memory performance from a strategic decision threshold. Task accuracy decreased with delay duration and sample/test proximity. When sample/test distances were small, older adults committed more false alarms than younger adults. The computational model explained the participants’ behavior well. The model parameters reflecting internal noise (not decision threshold) correlated with the precision of stimulus-selective cortical activity measured with MEG during the delay interval. The model uncovered an increase specifically in working memory noise in older compared with younger participants. Furthermore, in the MCI group, but not in the older healthy controls, internal noise correlated with the participants’ clinically assessed cognitive integrity. Our results are consistent with the idea that the stability of working memory contents deteriorates in aging, in a manner that is specifically linked to the overall cognitive integrity of individuals diagnosed with MCI.

衰老伴随着工作记忆的衰退，工作记忆是一种重要的认知能力，涉及刺激呈现后持续存在的刺激选择性神经活动。在这里，我们结合行为建模、神经心理学评估和大脑活动的 MEG 记录，揭示了老年人（男性和女性）的工作记忆动态，包括那些被诊断为轻度认知障碍 (MCI) 的人。仅通过行为建模对年轻人（男性和女性）进行研究。参与者在系统控制样本和测试刺激之间的延迟和距离的情况下执行视觉空间延迟匹配样本任务。他们的行为（匹配/不匹配决策）符合计算模型，允许将工作记忆性能背后的内部操作中的噪声与战略决策阈值分离。任务准确性随着延迟持续时间和样本/测试接近度而降低。当样本/测试距离很小时，老年人比年轻人误报更多。计算模型很好地解释了参与者的行为。反映内部噪声（而非决策阈值）的模型参数与延迟间隔期间用 MEG 测量的刺激选择性皮层活动的精度相关。该模型发现，与年轻参与者相比，老年人的工作记忆噪音明显增加。此外，在 MCI 组中，内部噪音与参与者临床评估的认知完整性相关，但在老年健康对照组中则不然。 我们的结果与这样的观点是一致的，即工作记忆内容的稳定性随着年龄的增长而恶化，其方式与被诊断为 MCI 的个体的整体认知完整性特别相关。