Section of Computational Cognitive Neuroscience, Department of Neurophysiology & Pathophysiology, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany
Department of Psychiatry, University Medical Center Hamburg-Eppendorf, Hamburg 20246, Germany.
J Neurosci. 2024 Jun 26;44(26):e1883232024. doi: 10.1523/JNEUROSCI.1883-23.2024.
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能力的下降，工作记忆是一种重要的认知能力，涉及到刺激选择神经活动，这种活动在刺激呈现后仍然存在。在这里，我们使用行为建模、神经心理学评估和大脑活动的 MEG 记录，揭示了老年成年人（男性和女性），包括被诊断为轻度认知障碍（MCI）的成年人的工作记忆动态。年轻成年人（男性和女性）仅进行行为建模研究。参与者在系统地操纵延迟和样本与测试刺激之间的距离的情况下，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）与计算模型拟合，该模型允许将工作记忆表现背后的内部操作中的噪声与策略决策阈值分离开来。随着延迟持续时间和样本/测试接近度的增加，任务准确性降低。当样本/测试距离较小时，老年成年人比年轻成年人犯更多的误报。计算模型很好地解释了参与者的行为。反映内部噪声（而不是决策阈值）的模型参数与在延迟间隔期间使用 MEG 测量的刺激选择性皮质活动的精确性相关。该模型揭示了与年轻参与者相比，老年参与者的工作记忆噪声专门增加。此外，在 MCI 组中，但在老年健康对照组中，内部噪声与参与者的临床评估认知完整性相关。我们的结果与这样的观点一致，即工作记忆内容的稳定性在衰老过程中恶化，这种恶化与被诊断为 MCI 的个体的整体认知完整性特别相关。
