Cognitive flexibility allows us to adaptively switch between different responsibilities in important domains of our daily life. Previous work has elucidated the neurochemical basis underlying the ability to switch responses to a previously nonreinforced exemplar and to switch between attentional sets. However, the role of neuromodulators in task switching, the ability to rapidly switch between two or more cognitive tasks afforded by the same stimuli, is still poorly understood. We attempted to fill this gap by manipulating norepinephrine levels using stress manipulation (Study 1a, n = 48; between-group design), transcutaneous vagus nerve stimulation at two different intensities (Study 1b, n = 48; sham-controlled between-group design), and pharmacological manipulation (Study 2, n = 24; double-blind crossover design), all of which increased salivary cortisol measures. Participants repeatedly switched between two cognitive tasks (classifying a digit as high/low [Task 1] or as odd/even [Task 2]), depending on the preceding cue. On each trial, a cue indicated the task to be performed. The cue–stimulus interval was varied to manipulate the time to prepare for the switch. Participants showed typical switch costs, which decreased with the time available for preparation. None of the manipulations modulated the size of the switch costs or the preparation effect, as supported by frequentist and Bayesian model comparisons. Task-switching performance reflects a complex mix of cognitive control and bottom–up dynamics of task-set representations. Our findings suggest that norepinephrine does not affect either of these aspects of cognitive flexibility.

认知灵活性使我们能够自适应地在日常生活重要领域的不同职责之间切换。以前的工作已经阐明了将响应切换到以前未增强的示例和在注意力集之间切换的能力背后的神经化学基础。然而，神经调节剂在任务切换中的作用，即在相同刺激提供的两个或多个认知任务之间快速切换的能力，仍然知之甚少。我们试图通过使用压力操纵（研究 1a， n = 48；组间设计）、两种不同强度的经皮迷走神经刺激（研究 1b，n = 48；假控制组间设计）来操纵去甲肾上腺素水平来填补这一空白。) 和药理操作 (研究 2,n= 24; 双盲交叉设计），所有这些都增加了唾液皮质醇的测量。根据前面的提示，参与者在两个认知任务之间反复切换（将数字分类为高/低 [任务 1] 或奇数/偶数 [任务 2]）。在每次试验中，都会有一个提示指示要执行的任务。改变提示刺激间隔以控制准备转换的时间。参与者展示了典型的转换成本，随着准备时间的增加而降低。正如常客和贝叶斯模型比较所支持的那样，这些操作都没有调节转换成本或准备效果的大小。任务切换性能反映了认知控制和任务集表示的自下而上动态的复杂组合。