Zhou Ashley X, Duncan John, Mitchell Daniel J
MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom.
Imaging Neurosci (Camb). 2024 Jun 3;2. doi: 10.1162/imag_a_00185. eCollection 2024.
Default mode network (DMN) activity, measured with fMRI, typically increases during internally directed thought, and decreases during tasks that demand externally focused attention. However,Crittenden et al. (2015)andSmith et al. (2018)reported increased DMN activity during demanding external task switches between different cognitive domains, compared to within-domain switches and task repeats. This finding is hard to reconcile with many dominant views of DMN function. Here, we aimed to replicate this DMN task-switch effect in a similar paradigm and test whether it reflects increased representation of broader context, specifically of a scene presented behind the focal task. In the Core DMN, we found significant activity for all task switches, compared to task repeats, and stronger activity for switches between rest and task. Although the content of the background scene was attended, recalled, and neurally decodable, there was no evidence that this differed by switch type. Therefore, external task switches activated DMN without enhanced processing of the surrounding background. Surprisingly, DMN activity at within-domain switches was no less than at between-domain switches. We suggest that modulation of DMN activity by task switches reflects a shift in the current cognitive model and depends on the overall complexity of that model.
使用功能磁共振成像（fMRI）测量的默认模式网络（DMN）活动，通常在内部导向思维期间增加，而在需要外部注意力集中的任务期间减少。然而，克里滕登等人（2015年）和史密斯等人（2018年）报告称，与域内切换和任务重复相比，在不同认知域之间进行要求较高的外部任务切换期间，DMN活动增加。这一发现很难与许多关于DMN功能的主流观点相协调。在这里，我们旨在在类似的范式中复制这种DMN任务切换效应，并测试它是否反映了更广泛背景的增加表征，特别是焦点任务背后呈现的场景。在核心DMN中，与任务重复相比，我们发现所有任务切换都有显著活动，而休息与任务之间的切换活动更强。尽管背景场景的内容被关注、回忆且可通过神经解码，但没有证据表明这种情况因切换类型而异。因此，外部任务切换激活了DMN，但没有增强对周围背景的处理。令人惊讶的是，域内切换时的DMN活动不少于域间切换时的活动。我们认为，任务切换对DMN活动的调节反映了当前认知模型的转变，并取决于该模型的整体复杂性。
