Reduced task-switching flexibility in parietal-cingulate and frontal circuits associated with brooding

Ruminative brooding is marked by its perseverative nature. Existing mechanistic theories attribute this to cognitive control deficits linked to elevated functional connectivity within the default mode network and abnormal prefrontal activity. Here, we conceptualize ruminative brooding as an emergent property of a neural attractor state within the default mode network. Stable attractors are mathematically defined by two key properties: 1) convergence over time (assessing attractivity), and 2) resistance to perturbation (assessing stability). We tested whether brain states associated with brooding exhibited these properties in healthy volunteers using EEG during a task-switching protocol that interleaved cued rumination, working memory, and autobiographical memory tasks. Since cued rumination and working memory are thought to engage anticorrelated networks (default mode vs. central executive), switching from cued rumination to working memory effectively “perturbs” this system. Cued rumination was associated with beta power in the posterior cingulate cortex, with rumination disengagement marked by a reduction in beta power in posterior parietal and cingulate cortices. Moreover, high trait rumination was associated with impaired disengagement of these rumination-related dynamics and reduced recruitment of the dlPFC when transitioning from cued rumination to the working memory task, consistent with the “resistance to perturbation” criterion of a stable attractor. Furthermore, trait brooding was positively associated with a reduction in variance in posterior parietal and cingulate cortices time series over the course of cued rumination trials, consistent with the “convergence” criterion. These results provide support for framing brooding-related neural dynamics as pathological attractor states, providing a mechanistic account of rumination’s perseverative quality.