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Grall, C.

Publications and source records attributed to Grall, C..

2 recordsLinked to original sources

Narrative 'twist' shifts within-individual neural representations of dissociable story features

Given the same input, understanding of that input can differ depending on context. How does the brain represent the latent mental frameworks that support different interpretations of the same sensory information? In this study, participants listened to the same auditory narrative twice; the narrative had a plot twist in the middle that dramatically shifted interpretations of the story. Using a within-subject design that held both the stimulus and the individual constant, we leveraged reinterpretation-driven shifts in neural activity between the two listens to identify where representations of different narrative elements are updated under a new interpretative framework. We separated the narrative into three interrelated levels--the overall narrative model, episodes, and characters--to determine where reinterpretation-driven updates to each element were reflected in brain activity. Neural activity patterns associated with interpretations and reinterpretations of these three elements were observed in overlapping but partially distinct sets of temporal, parietal, and prefrontal regions. Results suggest that heteromodal cortex represents specific narrative elements according not to their surface features, but to latent conceptual frameworks for understanding those elements, which can shift under a new narrative interpretation. Significance statementInformation is never experienced the same way twice. Here, we investigated where and how interpretations are updated in the brain when sensory input remains identical but contextual knowledge changes how we interpret that input. We used a unique narrative stimulus with a mid-story plot twist, which participants listened to twice. We found that sets of relatively dissociable regions across the brain represent three distinct narrative elements--narrative models, episodes, and characters. These findings reveal the neural basis for how identical information is processed differently through the mental frameworks we bring to understanding it.

neuroscience↗

Reliability of fMRI time series:Similarity of neural processing during movie viewing

Despite its widespread use in neuroscience, the reliability of fMRI remains insufficiently understood. One powerful way to tap into aspects of fMRI reliability is via the inter-subject correlation (ISC) approach, which exposes different viewers to the same time-locked naturalistic stimulus and assesses the similarity of neural time series. Here we examined the correlations of fMRI time series from 24 participants who watched the same movie clips across three repetitions. This enabled us to examine inter-subject correlations, intra-subject correlations, and correlations between aggregated time series, which we link to the notions of inter-rater reliability, stability, and consistency. In primary visual cortex we found average pairwise inter-subject correlations of about r = 0.3, and intra-subject correlations of similar magnitude. Aggregation across subjects increased inter-subject (inter-group) correlations to r = 0.87, and additional intra-subject averaging before cross-subject aggregation yielded correlations of r = 0.93. Computing the same analyses for parietal (visuospatial network) and cingulate cortices (saliency network) revealed a gradient of decreasing ISC from primary visual to higher visual to post-perceptual regions. These latter regions also benefitted most from the increased reliability due to aggregation. We discuss theoretical and practical implications of this link between neural process similarity and psychometric conceptions of inter-rater reliability, stability, and internal consistency.

neuroscience↗