Neural Evidence for Representational Persistence Within Events

Abstract

How does the brain process continuous experiences so they can be remembered? Evidence suggests that people perceive their experience as a series of distinct and meaningful events. Information encountered within the same event shows greater temporal integration into memory as well as enhanced neural representational similarity. Although these data support the theory that the brain builds and maintains a mental model of the current event that represents recently encountered stimulus information, this hypothesis has not been directly tested. We used fMRI in humans (N = 21, 13 female) to test whether within-event neural similarity indicates the persistence of stimulus representations in a mental model. Participants viewed trial-unique visual images that were grouped into events. We calculated neural pattern similarity across time in the category-selective visual cortex to measure stimulus persistence. Pattern similarity was enhanced within, compared with between, events in the object-sensitive left lateral occipital (LO) cortex. This was specific to situations when objects could persist within a mental model, suggesting modulation of neural activity based on the features and structure of the event. Left LO object persistence was correlated with activity in a medial prefrontal cortex (mPFC) region linked to representing mental models within events. mFPC activity also correlated with pattern similarity in the hippocampus but more generally across stimulus categories. Critically, left LO similarity was related to estimates of temporal proximity in memory. The data suggest that temporal neural stability reflects stimulus persistence in mental models and highlight the importance of within-event representational stability in the transformation of experience to memory.

SIGNIFICANCE STATEMENT How does the brain process continuous experiences so they can be remembered? One idea is that information persists in mental models during stable events, facilitating the organization of events in memory. Using fMRI pattern similarity analysis, we found enhanced similarity within, compared with between, events in the object-sensitive LO but only when objects could persist within a mental model. mPFC activity correlated with left LO similarity when objects persisted within an event; in contrast, mPFC activity correlated with hippocampal similarity across stimulus categories. Left LO persistence was also related to the remembered temporal proximity of stimuli. The data suggest the brain dynamically maintains stimulus information in mental models during events, supporting the transformation of experience into memory.