Department of Neuroscience, McGill Univ., Montreal, QC, H3A 2 T5, Canada.
Douglas Mental Health University Institute Department of Psychiatry, McGill Univ., Montreal, QC, H4H 1R3, Canada.
Neuroimage. 2014 Apr 1;89:244-55. doi: 10.1016/j.neuroimage.2013.11.050. Epub 2013 Dec 6.
We investigated the role of distinct regions of the default-mode network (DMN) during memory encoding with fMRI. Subjects encoded words using either a strategy that emphasized self-referential (pleasantness) processing, or one that emphasized semantic (man-made/natural) processing. During encoding subjects were intermittently presented with thought probes to evaluate if they were concentrated and on-task or exhibiting task-unrelated thoughts (TUT). After the scanning session subjects performed a source retrieval task to determine which of two judgments they performed for each word at encoding. Source retrieval accuracy was higher for words encoded with the pleasantness vs. the man-made/natural task and there was a trend for higher performance for words preceding on-task vs. TUT reports. fMRI results show that left anterior medial PFC and left angular gyrus activity was greater during successful vs. unsuccessful encoding during both encoding tasks. Greater activity in left anterior cingulate and bilateral lateral temporal cortex was related successful vs. unsuccessful encoding only in the pleasantness task. In contrast, posterior cingulate, right anterior cingulate and right temporoparietal junction were activated to a greater extent in unsuccessful vs. successful encoding across tasks. Finally, activation in posterior cingulate and bilateral dorsolateral prefrontal cortex was related to TUT across tasks; moreover, we observed a conjunction in posterior cingulate between encoding failure and TUT. We conclude that DMN regions play dissociable roles during memory formation, and that their association with subsequent memory may depend on the manner in which information is encoded and retrieved.
我们使用 fMRI 研究了默认模式网络（DMN）不同区域在记忆编码过程中的作用。被试者使用强调自我参照（愉悦感）处理的策略或强调语义（人为/自然）处理的策略来编码单词。在编码过程中，被试者会间歇性地接受思维探针，以评估他们是否专注和在任务中，或者是否表现出与任务无关的思维（TUT）。扫描会话结束后，被试者执行源检索任务，以确定他们在编码时对每个单词执行了哪两个判断。与在人为/自然任务中相比，用愉悦感任务编码的单词的源检索准确性更高，并且在与任务相关的报告相比，在任务相关的报告之前的单词表现出更高的性能趋势。 fMRI 结果表明，在两种编码任务中，左前内侧额上回和左角回在成功编码与不成功编码期间的活动更大。在愉悦感任务中，左前扣带和双侧外侧颞叶皮层的更大活动与成功与不成功的编码相关，而在其他任务中则没有。相比之下，后扣带、右前扣带和右颞顶连接在所有任务中不成功编码与成功编码相比激活程度更高。最后，后扣带和双侧背外侧前额叶皮层的激活与所有任务中的 TUT 相关；此外，我们在后扣带中观察到与编码失败和 TUT 的联合。我们得出的结论是，DMN 区域在记忆形成过程中发挥着不同的作用，并且它们与随后的记忆的关联可能取决于信息编码和检索的方式。
