Brains striving for coherence: Long-term cumulative plot formation in the default mode network

Abstract

Many everyday activities, such as engaging in conversation or listening to a story, require us to sustain attention over a prolonged period of time while integrating and synthesizing complex episodic content into a coherent mental model. Humans are remarkably capable of navigating and keeping track of all the parallel social activities of everyday life even when confronted with interruptions or changes in the environment. However, the underlying cognitive and neurocognitive mechanisms of such long-term integration and profiling of information remain a challenge to neuroscience. While brain activity is generally traceable within the short time frame of working memory (milliseconds to seconds), these integrative processes last for minutes, hours or even days. Here we report two experiments on story comprehension. Experiment I establishes a cognitive dissociation between our comprehension of plot and incidental facts in narratives: when episodic material allows for long-term integration in a coherent plot, we recall fewer factual details. However, when plot formation is challenged, we pay more attention to incidental facts. Experiment II investigates the neural underpinnings of plot formation. Results suggest a central role for the brain's default mode network related to comprehension of coherent narratives while incoherent episodes rather activate the frontoparietal control network. Moreover, an analysis of cortical activity as a function of the cumulative integration of narrative material into a coherent story reveals to linear modulations of right hemisphere posterior temporal and parietal regions. Together these findings point to key neural mechanisms involved in the fundamental human capacity for cumulative plot formation.

Revealing the neural networks that extract conceptual gestalts from continuously evolving or changing semantic contexts

“…Accordingly, in this functional magnetic resonance imaging (fMRI) study we established the brain regions and networks that support time-extended semantic integration (formation of the semantic gestalt), as well as those that are sensitive to changes in semantic context (update of the semantic gestalt). Importantly, in doing so we provide some timely evidence that bridges the existing work on narratives (Hasson et al, 2008;Lerner et al, 2011;Simony et al, 2016;Tylen et al, 2015) with the broader neurocognitive theories of semantic cognition .…”

“…Other studies, instead, have measured multi-item semantic combinations without task manipulations that distinguish between brain structures involved in semantic integration (or formation of the semantic gestalt) from those involved in extrasemantic neurocomputations (e.g., working memory (WM), attentional control, etc. : e.g., (Hasson et al, 2008;Lerner et al, 2011;Simony et al, 2016;Tylen et al, 2015). Accordingly, in this functional magnetic resonance imaging (fMRI) study we established the brain regions and networks that support time-extended semantic integration (formation of the semantic gestalt), as well as those that are sensitive to changes in semantic context (update of the semantic gestalt).…”

“…In detail, the networks associated with dorsal executive and semantic control should be critically important for update of the semantic gestalt (i.e., LC>HC), as they have been shown to engage whenever semantic processing is demanding Noonan et al, 2013;Tylen et al, 2015) or after changes of non-semantic rules (Vatansever et al, 2017b). Furthermore, the DMN -a network comprising midline brain regions and the angular gyrus (AG) -which is often anticorrelated with the dorsal executive network (Fox et al, 2005;Humphreys and Lambon Ralph, 2017;Spreng et al, 2010;Vincent et al, 2008, but see Dixon et al, 2017 -might also be a crucial network for the formation of conceptual gestalts.…”

Psychology, meaning making, and the study of worldviews: Beyond religion and non-religion.

“…The hypothetical slow process is effectively an extension of working memory, integrating episodic and semantic content over longer spans of time in order to guide long-term patterns of behavior across changing contexts. Neuroimaging studies suggest that narrative synthesis is mediated by major hubs of the DMN, including the medial prefrontal cortex, posterior cingulate/precuneus, and temporo-parietal junction, which integrate multisensory information across medium-to-long spans of time (Tylen et al, 2015;Lerner et al, 2011 The emergence and development of ToM, MTT, and the "slow process" of narrative synthesis all reflect a more basic cognitive shift in the nature of representation, from concrete to abstract (Donald, 1991;Deacon, 1997). The objects of cognition are no longer bound to physical referents in the present situation, but include counterfactual worlds and abstract concepts that can be shared through language.…”

Time regained: how the human brain constructs memory for time

“…In these studies, brain activity is examined during processing of a stream of audio or film clips, from which the content of temporally separate clips can be meaningfully integrated into a coherent sequence of events. One such study [48] found that activity in the PM network was higher in magnitude during processing of coherent audio clips when compared with clips that did not comprise a coherent sequence of events (incoherent). Milivojevic et al [49] compared brain activity patterns as participants watched a continuous movie in which odd-numbered and even-numbered scenes depicted two different coherent narratives involving the same characters and spatial contexts.…”