Rac-Lubashevsky Rachel, Kessler Yoav
Department of Brain and Cognitive Sciences and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Israel.
Department of Psychology and Zlotowski Center for Neuroscience, Ben-Gurion University of the Negev, Israel.
Neuropsychologia. 2016 Sep;90:190-9. doi: 10.1016/j.neuropsychologia.2016.07.013. Epub 2016 Jul 15.
Working memory (WM) has two major functions: Maintenance, which is the ability to shield information from being overwritten by irrelevant information, and updating, the ability to modify the maintained information when needed. These two conflicting demands are suggested to be controlled by a gating mechanism (for review see O'Reilly (2006)) which enables selective control over updating. Information is robustly maintained in WM when the gate is closed, while opening the gate enables updating. In the present study, we utilized the reference-back paradigm in order to examine their unique contribution to individual differences in n-back, presumably the most widely-used WM updating task. The reference-back is composed of two types of trials: reference trials which require both matching (i.e., a same/different judgment) and WM updating, and comparison trials which require matching and maintenance. Eighty-eight participants performed the following tasks: 2-choice RT, 1-back, 2-back and the reference-back task. A multiple regression approach was taken in order to explain individual differences in 1-back and 2-back. The reference-back task enabled separating the contribution of the matching decision (difference between mismatch and match), gate-opening (the switch cost in reference trials), gate closing (the switch cost in comparison trials) and WM updating (the difference between reference and comparison trials) to task performance. An intrusion component (WM based proactive interference) was also calculated from 2-back performance. The results indicate that RT in 1-back is mainly predicted by gate opening and by WM updating while 2-back is mainly predicted by gate closing and intrusion. These results confirmed that n-back is not merely an updating task, but also that controlling the contents of WM is the main source of individual differences in the task. The implications for understanding the n-back task and WM updating in general are discussed.
工作记忆（WM）有两个主要功能：维持，即保护信息不被无关信息覆盖的能力；更新，即根据需要修改已维持信息的能力。这两种相互冲突的需求被认为是由一种门控机制控制的（综述见奥赖利（2006年）），该机制能够对更新进行选择性控制。当门关闭时，信息在工作记忆中得到稳健维持，而打开门则允许更新。在本研究中，我们采用回溯参照范式来检验它们对n-back任务中个体差异的独特贡献，n-back任务可能是使用最广泛的工作记忆更新任务。回溯参照由两种类型的试验组成：需要匹配（即相同/不同判断）和工作记忆更新的参照试验，以及需要匹配和维持的比较试验。88名参与者完成了以下任务：二选一反应时任务、1-back任务、2-back任务和回溯参照任务。为了解释1-back和2-back任务中的个体差异，我们采用了多元回归方法。回溯参照任务能够区分匹配决策（错配与匹配之间的差异）、开门（参照试验中的切换成本）、关门（比较试验中的切换成本）和工作记忆更新（参照试验与比较试验之间的差异）对任务表现的贡献。还根据2-back任务的表现计算了一个干扰成分（基于工作记忆的前摄干扰）。结果表明，1-back任务的反应时主要由开门和工作记忆更新预测，而2-back任务的反应时主要由关门和干扰预测。这些结果证实，n-back任务不仅仅是一个更新任务，而且控制工作记忆的内容是该任务中个体差异的主要来源。本文还讨论了这些结果对理解n-back任务和一般工作记忆更新的意义。
