Department of Psychiatry and Behavioral Science, Duke University School of Medicine, Durham, North Carolina, United States of America.
Department of Neurology, Duke University School of Medicine, Durham, North Carolina, United States of America.
PLoS One. 2019 Mar 22;14(3):e0213707. doi: 10.1371/journal.pone.0213707. eCollection 2019.
Working memory is the ability to perform mental operations on information that is stored in a flexible, limited capacity buffer. The ability to manipulate information in working memory is central to many aspects of human cognition, but also declines with healthy aging. Given the profound importance of such working memory manipulation abilities, there is a concerted effort towards developing approaches to improve them. The current study tested the capacity to enhance working memory manipulation with online repetitive transcranial magnetic stimulation in healthy young and older adults. Online high frequency (5Hz) repetitive transcranial magnetic stimulation was applied over the left dorsolateral prefrontal cortex to test the hypothesis that active repetitive transcranial magnetic stimulation would lead to significant improvements in memory recall accuracy compared to sham stimulation, and that these effects would be most pronounced in working memory manipulation conditions with the highest cognitive demand in both young and older adults. Repetitive transcranial magnetic stimulation was applied while participants were performing a delayed response alphabetization task with three individually-titrated levels of difficulty. The left dorsolateral prefrontal cortex was identified by combining electric field modeling to individualized functional magnetic resonance imaging activation maps and was targeted during the experiment using stereotactic neuronavigation with real-time robotic guidance, allowing optimal coil placement during the stimulation. As no accuracy differences were found between young and older adults, the results from both groups were collapsed. Subsequent analyses revealed that active stimulation significantly increased accuracy relative to sham stimulation, but only for the hardest condition. These results point towards further investigation of repetitive transcranial magnetic stimulation for memory enhancement focusing on high difficulty conditions as those most likely to exhibit benefits.
工作记忆是指在灵活且容量有限的缓冲区中对存储的信息进行心理操作的能力。在工作记忆中操纵信息的能力是人类认知的许多方面的核心，但随着健康衰老，这种能力也会下降。鉴于这种工作记忆操作能力的重要性，人们正在共同努力开发改善这些能力的方法。本研究测试了在健康的年轻和老年成年人中通过在线重复经颅磁刺激来增强工作记忆操作的能力。在线高频（5Hz）重复经颅磁刺激施加于左背外侧前额叶皮层，以检验以下假设：与假刺激相比，主动重复经颅磁刺激将显著提高记忆召回准确性；在工作记忆操作条件下，这种效果在认知需求最高的情况下最为明显，而这种认知需求在年轻和老年成年人中都是最高的。在进行延迟反应字母排序任务时，对参与者施加重复经颅磁刺激，该任务有三个单独调整难度的级别。通过将电场建模与个体化功能磁共振成像激活图相结合来确定左背外侧前额叶皮层，并在实验过程中使用立体定向神经导航和实时机器人引导来靶向该区域，以在刺激过程中实现最佳线圈放置。由于在年轻和老年成年人之间未发现准确性差异，因此将两组的结果合并。随后的分析表明，与假刺激相比，主动刺激显著提高了准确性，但仅在最难的条件下如此。这些结果表明，进一步研究针对高难度条件的重复经颅磁刺激以增强记忆力是有必要的，因为这些条件最有可能受益。
