Wang Liping, Li Xianchun, Hsiao Steven S, Lenz Fred A, Bodner Mark, Zhou Yong-Di, Fuster Joaquín M
Key Laboratory of Brain Functional Genomics (Ministry of Education & Science and Technology Commission of Shanghai Municipality), Institute of Cognitive Neuroscience, School of Psychology and Cognitive Science, East China Normal University, Shanghai 200062, China; NYU-ECNU Institute of Brain and Cognitive Science at NYU Shanghai, Shanghai 200062, China;
Key Laboratory of Brain Functional Genomics (Ministry of Education & Science and Technology Commission of Shanghai Municipality), Institute of Cognitive Neuroscience, School of Psychology and Cognitive Science, East China Normal University, Shanghai 200062, China;
Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):E214-9. doi: 10.1073/pnas.1410130112. Epub 2014 Dec 24.
Previous studies have shown that neurons of monkey dorsolateral prefrontal cortex (DLPFC) integrate information across modalities and maintain it throughout the delay period of working-memory (WM) tasks. However, the mechanisms of this temporal integration in the DLPFC are still poorly understood. In the present study, to further elucidate the role of the DLPFC in crossmodal WM, we trained monkeys to perform visuo-haptic (VH) crossmodal and haptic-haptic (HH) unimodal WM tasks. The neuronal activity recorded in the DLPFC in the delay period of both tasks indicates that the early-delay differential activity probably is related to the encoding of sample information with different strengths depending on task modality, that the late-delay differential activity reflects the associated (modality-independent) action component of haptic choice in both tasks (that is, the anticipation of the behavioral choice and/or active recall and maintenance of sample information for subsequent action), and that the sustained whole-delay differential activity likely bridges and integrates the sensory and action components. In addition, the VH late-delay differential activity was significantly diminished when the haptic choice was not required. Taken together, the results show that, in addition to the whole-delay differential activity, DLPFC neurons also show early- and late-delay differential activities. These previously unidentified findings indicate that DLPFC is capable of (i) holding the coded sample information (e.g., visual or tactile information) in the early-delay activity, (ii) retrieving the abstract information (orientations) of the sample (whether the sample has been haptic or visual) and holding it in the late-delay activity, and (iii) preparing for behavioral choice acting on that abstract information.
以往的研究表明，猴子背外侧前额叶皮质（DLPFC）的神经元能够跨模态整合信息，并在工作记忆（WM）任务的延迟期内保持该信息。然而，DLPFC中这种时间整合的机制仍知之甚少。在本研究中，为了进一步阐明DLPFC在跨模态WM中的作用，我们训练猴子执行视觉-触觉（VH）跨模态和触觉-触觉（HH）单模态WM任务。在两项任务的延迟期记录到的DLPFC神经元活动表明，早期延迟差异活动可能与根据任务模态以不同强度对样本信息进行编码有关，晚期延迟差异活动反映了两项任务中触觉选择的相关（模态无关）动作成分（即对行为选择的预期和/或对样本信息的主动回忆及维持以用于后续动作），而持续的整个延迟期差异活动可能连接并整合了感觉和动作成分。此外，当不需要触觉选择时，VH晚期延迟差异活动显著减弱。综上所述，结果表明，除了整个延迟期差异活动外，DLPFC神经元还表现出早期和晚期延迟差异活动。这些先前未被发现的结果表明，DLPFC能够（i）在早期延迟活动中保存编码的样本信息（如视觉或触觉信息），（ii）提取样本的抽象信息（方向）（无论样本是触觉还是视觉的）并将其保存在晚期延迟活动中，以及（iii）为基于该抽象信息的行为选择做准备。
