Department of Experimental Psychology, University of Oxford, OX1 3SR, Oxford, UK.
Graduate School of Frontier Biosciences, Osaka University, Osaka, 565-0871, Japan.
Nat Commun. 2023 Aug 19;14(1):5054. doi: 10.1038/s41467-023-40676-1.
While classic views proposed that working memory (WM) is mediated by sustained firing, recent evidence suggests a contribution of activity-silent states. Within WM, human neuroimaging studies suggest a switch between attentional foreground and background, with only the foregrounded item represented in active neural firing. To address this process at the cellular level, we recorded prefrontal (PFC) and posterior parietal (PPC) neurons in a complex problem-solving task, with monkeys searching for one or two target locations in a first cycle of trials, and retaining them for memory-guided revisits on subsequent cycles. When target locations were discovered, neither frontal nor parietal neurons showed sustained goal-location codes continuing into subsequent trials and cycles. Instead there were sequences of timely goal silencing and reactivation, and following reactivation, sustained states until behavioral response. With two target locations, goal representations in both regions showed evidence of transitions between foreground and background, but the PFC representation was more complete, extending beyond the current trial to include both past and future selections. In the absence of unbroken sustained codes, different neuronal states interact to support maintenance and retrieval of WM representations across successive trials.
虽然经典观点认为工作记忆 (WM) 是由持续放电介导的，但最近的证据表明活动静默状态也有贡献。在 WM 中，人类神经影像学研究表明注意力的前景和背景之间存在切换，只有前景项目在活跃的神经放电中被表示。为了在细胞水平上解决这个问题，我们在一个复杂的解决问题任务中记录了前额叶 (PFC) 和顶后 (PPC) 神经元，在最初的试验循环中，猴子寻找一个或两个目标位置，并在随后的循环中保留它们以进行记忆引导的重访。当目标位置被发现时，无论是额皮质还是顶皮质神经元都没有显示出持续的目标位置编码，这些编码会持续到后续的试验和循环中。相反，有一系列及时的目标沉默和重新激活，并且在重新激活之后，会有持续的状态直到行为反应。对于两个目标位置，两个区域的目标表示都显示出在前景和背景之间转换的证据，但 PFC 的表示更为完整，不仅包括当前试验，还包括过去和未来的选择。在没有持续不断的持续编码的情况下，不同的神经元状态相互作用，以支持连续试验中 WM 表示的维持和检索。
