Roberts Brooke M, Libby Laura A, Inhoff Marika C, Ranganath Charan
Center for Neuroscience, University of California at Davis, Davis, CA 95618, United States.
Department of Psychology, University of California at Davis, Davis, CA 95616, United States.
Behav Brain Res. 2018 Nov 15;354:55-63. doi: 10.1016/j.bbr.2017.05.068. Epub 2017 Jun 8.
Maintaining items in an appropriate sequence is important for many daily activities; however, remarkably little is known about the neural basis of human temporal working memory. Prior work suggests that the prefrontal cortex (PFC) and medial temporal lobe (MTL), including the hippocampus, play a role in representing information about temporal order. The involvement of these areas in successful temporal working memory, however, is less clear. Additionally, it is unknown whether regions in the PFC and MTL support temporal working memory across different timescales, or at coarse or fine levels of temporal detail. To address these questions, participants were scanned while completing 3 working memory task conditions (Group, Position and Item) that were matched in terms of difficulty and the number of items to be actively maintained. Group and Position trials probed temporal working memory processes, requiring the maintenance of hierarchically organized coarse and fine temporal information, respectively. To isolate activation related to temporal working memory, Group and Position trials were contrasted against Item trials, which required detailed working memory maintenance of visual objects. Results revealed that working memory encoding and maintenance of temporal information relative to visual information was associated with increased activation in dorsolateral PFC (DLPFC), and perirhinal cortex (PRC). In contrast, maintenance of visual details relative to temporal information was characterized by greater activation of parahippocampal cortex (PHC), medial and anterior PFC, and retrosplenial cortex. In the hippocampus, a dissociation along the longitudinal axis was observed such that the anterior hippocampus was more active for working memory encoding and maintenance of visual detail information relative to temporal information, whereas the posterior hippocampus displayed the opposite effect. Posterior parietal cortex was the only region to show sensitivity to temporal working memory across timescales, and was particularly involved in the encoding and maintenance of fine temporal information relative to maintenance of temporal information at more coarse timescales. Collectively, these results highlight the involvement of PFC and MTL in temporal working memory processes, and suggest a dissociation in the type of working memory information represented along the longitudinal axis of the hippocampus.
在许多日常活动中，以适当的顺序维持事物很重要；然而，对于人类颞叶工作记忆的神经基础，我们所知甚少。先前的研究表明，前额叶皮层（PFC）和内侧颞叶（MTL），包括海马体，在表征时间顺序信息方面发挥作用。然而，这些区域在成功的颞叶工作记忆中的参与情况尚不清楚。此外，PFC和MTL中的区域是否在不同时间尺度上，或在时间细节的粗略或精细水平上支持颞叶工作记忆也未知。为了解决这些问题，在参与者完成3种工作记忆任务条件（组、位置和项目）时对他们进行扫描，这些条件在难度和需要积极维持的项目数量方面相匹配。组和位置试验探测颞叶工作记忆过程，分别需要维持层次组织的粗略和精细时间信息。为了分离与颞叶工作记忆相关的激活，将组和位置试验与项目试验进行对比，项目试验需要对视觉对象进行详细的工作记忆维持。结果显示，相对于视觉信息，颞叶信息的工作记忆编码和维持与背外侧前额叶皮层（DLPFC）和鼻周皮层（PRC）的激活增加有关。相比之下，相对于颞叶信息，视觉细节的维持表现为海马旁皮层（PHC）、内侧和前额叶皮层以及压后皮层的更大激活。在海马体中，观察到沿纵轴的分离，即相对于颞叶信息，前海马体在视觉细节信息的工作记忆编码和维持方面更活跃，而后海马体则表现出相反的效果。后顶叶皮层是唯一在不同时间尺度上对颞叶工作记忆敏感的区域，并且特别参与相对于更粗略时间尺度上的颞叶信息维持的精细时间信息的编码和维持。总的来说，这些结果突出了PFC和MTL在颞叶工作记忆过程中的参与，并表明在海马体纵轴上所表征的工作记忆信息类型存在分离。
