Murray Linda J, Ranganath Charan
Center for Neuroscience and Department of Psychology, University of California at Davis, Davis, California 95616, USA.
J Neurosci. 2007 May 16;27(20):5515-22. doi: 10.1523/JNEUROSCI.0406-07.2007.
Results from neuroimaging studies of long-term memory (LTM) encoding have contributed to the view that the ventrolateral prefrontal cortex (VLPFC) contributes to successful LTM formation, whereas the dorsolateral prefrontal cortex (DLPFC) does not. We hypothesized that the DLPFC does contribute to LTM, but under specific circumstances. That is, the DLPFC may be critical for building relationships between items during on-line processing, and this may promote LTM for associations between items. We used event-related functional magnetic resonance imaging (fMRI) to test this hypothesis by examining brain activity during sequential encoding of unrelated word pairs. During presentation of the second ("target") word in each pair, subjects either made a semantic judgment specific to the target word ("item-specific" trials), or a semantic judgment that involved a comparison between the target word and the first word in the pair ("relational" trials). Behaviorally, recognition memory for target words was equivalent between the two trial types but associative recognition of studied word pairs was significantly greater for relational trials. fMRI results showed that DLPFC activity was greater during relational compared with item-specific encoding and that DLPFC activity predicted successful memory for associations but not successful item memory. Activity in the VLPFC was also greater for relational compared with item-specific encoding, but VLPFC activation predicted successful memory for both associations and items. These results support the view that the DLPFC may contribute to LTM through its role in active processing of relationships during encoding, whereas the VLPFC may have a more general role in promoting successful LTM formation.
长期记忆（LTM）编码的神经影像学研究结果支持了这样一种观点，即腹外侧前额叶皮层（VLPFC）有助于成功形成长期记忆，而背外侧前额叶皮层（DLPFC）则不然。我们推测，DLPFC确实对长期记忆有贡献，但仅限于特定情况。也就是说，DLPFC可能在在线处理过程中对建立项目之间的关系至关重要，而这可能会促进对项目之间关联的长期记忆。我们使用事件相关功能磁共振成像（fMRI）来检验这一假设，通过检查无关单词对的顺序编码过程中的大脑活动。在每对单词中的第二个（“目标”）单词呈现期间，受试者要么对目标单词进行特定的语义判断（“特定项目”试验），要么进行涉及目标单词与该对中的第一个单词之间比较的语义判断（“关系”试验）。在行为上，两种试验类型中对目标单词的识别记忆相当，但关系试验中对所学单词对的关联识别明显更高。fMRI结果显示，与特定项目编码相比，关系编码期间DLPFC的活动更强，并且DLPFC的活动预测了关联记忆的成功而非项目记忆的成功。与特定项目编码相比，关系编码期间VLPFC的活动也更强，但VLPFC的激活预测了关联和项目记忆的成功。这些结果支持了这样一种观点，即DLPFC可能通过其在编码过程中对关系的主动处理作用而有助于长期记忆，而VLPFC可能在促进成功的长期记忆形成方面具有更普遍的作用。
