Bergmann Heiko C, Daselaar Sander M, Beul Sarah F, Rijpkema Mark, Fernández Guillén, Kessels Roy P C
Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands.
Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, Netherlands ; Department of Computational Neuroscience, University Medical Center Hamburg-Eppendorf Hamburg, Germany.
Front Hum Neurosci. 2015 Sep 2;9:479. doi: 10.3389/fnhum.2015.00479. eCollection 2015.
Performance on working memory (WM) tasks may partially be supported by long-term memory (LTM) processing. Hence, brain activation recently being implicated in WM may actually have been driven by (incidental) LTM formation. We examined which brain regions actually support successful WM processing, rather than being confounded by LTM processes, during the maintenance and probe phase of a WM task. We administered a four-pair (faces and houses) associative delayed-match-to-sample (WM) task using event-related functional MRI (fMRI) and a subsequent associative recognition LTM task, using the same stimuli. This enabled us to analyze subsequent memory effects for both the WM and the LTM test by contrasting correctly recognized pairs with incorrect pairs for either task. Critically, with respect to the subsequent WM effect, we computed this analysis exclusively for trials that were forgotten in the subsequent LTM recognition task. Hence, brain activity associated with successful WM processing was less likely to be confounded by incidental LTM formation. The subsequent LTM effect, in contrast, was analyzed exclusively for pairs that previously had been correctly recognized in the WM task, disclosing brain regions involved in successful LTM formation after successful WM processing. Results for the subsequent WM effect showed no significantly activated brain areas for WM maintenance, possibly due to an insensitivity of fMRI to mechanisms underlying active WM maintenance. In contrast, a correct decision at WM probe was linked to activation in the "retrieval success network" (anterior and posterior midline brain structures). The subsequent LTM analyses revealed greater activation in left dorsolateral prefrontal cortex and posterior parietal cortex in the early phase of the maintenance stage. No supra-threshold activation was found during the WM probe. Together, we obtained clearer insights in which brain regions support successful WM and LTM without the potential confound of the respective memory system.
工作记忆（WM）任务的表现可能部分由长期记忆（LTM）处理所支持。因此，最近与WM相关的大脑激活实际上可能是由（偶然的）LTM形成所驱动的。我们研究了在WM任务的维持和探测阶段，哪些大脑区域实际上支持成功的WM处理，而不是被LTM过程所混淆。我们使用事件相关功能磁共振成像（fMRI）进行了一项四对（面孔和房屋）联想延迟匹配样本（WM）任务，并使用相同的刺激进行了后续的联想识别LTM任务。这使我们能够通过对比两项任务中正确识别的对与错误的对，来分析WM和LTM测试的后续记忆效应。至关重要的是，关于后续的WM效应，我们仅针对在后续LTM识别任务中被遗忘的试验进行了此分析。因此，与成功的WM处理相关的大脑活动不太可能被偶然的LTM形成所混淆。相比之下，后续的LTM效应仅针对先前在WM任务中被正确识别的对进行了分析，揭示了成功的WM处理后参与成功LTM形成的大脑区域。后续WM效应的结果显示，WM维持阶段没有显著激活的脑区，这可能是由于fMRI对活跃WM维持背后的机制不敏感。相比之下，WM探测时的正确决策与“检索成功网络”（大脑前后中线结构）的激活有关。后续的LTM分析显示，在维持阶段的早期，左背外侧前额叶皮层和顶叶后皮层有更大的激活。在WM探测期间未发现超阈值激活。总之，我们更清楚地了解了哪些大脑区域支持成功的WM和LTM，而没有各自记忆系统的潜在混淆。
