Brain meta-state transitions demarcate thoughts across task contexts, exposing the mental noise of trait neuroticism

Using new methods to capture streams of neural meta-state transitions in single participants, we characterize the psychological meaning of these regular neural events. Similar to past group-average-based analyses, participants individual transition streams aligned to meaningful events during movie-viewing. However, our individual-based approach also afforded observation of participants idiosyncratic transition timing at rest. Across these two dramatically different task contexts, transitions featured similar trait-like frequency, concurrence with activation of regions associated with spontaneous thought, and suppression by attention regions. Based on this generalization, as well as the centrality of semantics to thought, we argue transitions serve as a general, implicit neurobiological marker of new thoughts, and that their frequency therefore approximates participants mentation rate. Finally, to contribute convergent validity and illustrate the utility of our approach for thought dynamics, we regressed resting transition rate and movie-viewing group temporal conformity against trait neuroticism, yielding a first neural confirmation of the \"mental noise\" theory.