ABSTRACT

The aim of the present discussion paper was to identify whether any fMRI studies have provided convincing evidence that the hippocampus is associated with working memory. The key outcome variable was the phase in which hippocampal activity was observed: study, early delay, late delay, and/or test. During working memory tasks, long-term memory processes can operate during the study phase, early delay phase (due to extended encoding), or test phase. Thus, working memory processes can be isolated from long-term memory processes during only the late delay period. Twenty-six working memory studies that reported hippocampal activity were systematically analyzed. Many experimental protocol and analysis parameters were considered including number of participants, stimulus type(s), number of items during the study phase, delay duration, task during the test phase, behavioral accuracy, relevant fMRI contrast(s), whether the information was novel or familiar, number of phases modeled, and whether activation timecourses were extracted. For studies that were able to identify activity in different phases, familiar information sometimes produced activity during the study phase and/or test phase, but never produced activity during the delay period. When early-delay phase and late-delay phase activity could be distinguished via modeling these phases separately or inspecting activation timecourses, novel information could additionally produce activity during the early delay phase. There was no convincing evidence of hippocampal activity during the late delay period. These results indicate that working memory does not activate the hippocampus and suggest a model of working memory where maintenance of novel information can foster long-term memory encoding.

摘要

本讨论文件的目的是确定是否有任何功能磁共振成像研究提供了令人信服的证据证明海马体与工作记忆相关。关键结果变量是观察海马活动的阶段：研究、早期延迟、晚期延迟和/或测试。在工作记忆任务期间，长期记忆过程可以在学习阶段、早期延迟阶段（由于扩展编码）或测试阶段运行。因此，工作记忆过程可以仅在后期延迟期间与长期记忆过程隔离。系统分析了 26 项报告海马活动的工作记忆研究。考虑了许多实验方案和分析参数，包括参与者数量、刺激类型、研究阶段的项目数量、延迟持续时间、测试阶段的任务、行为准确性、相关功能磁共振成像对比、信息是新颖的还是熟悉的、建模的阶段数量以及是否提取了激活时间过程。对于能够识别不同阶段活动的研究，熟悉的信息有时会在研究阶段和/或测试阶段产生活动，但在延迟期间不会产生活动。当早期延迟阶段和晚期延迟阶段活动可以通过单独建模这些阶段或检查激活时间过程来区分时，新信息还可以在早期延迟阶段产生活动。在延迟后期没有令人信服的海马活动证据。