Schedule of Events | Symposia

Symposium Session 1 - Creating the structure of ongoing experience

Symposium Session 1: Sunday, March 30, 2025, 1:30 – 3:30 pm EDT, Grand Ballroom

Chair: James Antony¹; ¹California Polytechnic State University, San Luis Obispo
Presenters: Zachariah Reagh, Emily Finn, James Antony, Janice Chen

Although time flows continuously, we tend to chunk our experiences into discrete events. This chunking has been demonstrated behaviorally – via recall clustering within versus across events – and neurally – via stable neural patterns within events to rapid changes at event boundaries. However, real-world events are interrelated according to various forms of structure, meaning that successive neural states may reactivate prior states to link them and influence recall. In this symposium, we will tackle the behavioral and neural consequences of structure bridging across ongoing experiences. First, Zach Reagh will demonstrate that (1) similar neural states track individual people and relationships between people across multiple events, and that (2) memories of people distort the narrative timeline during recall. Next, Emily Finn will show (1) how the brain “unscrambles” chronological information from a nonlinear narrative by revisiting prior neural states and (2) how across-subject variability of neural event boundaries across the brain predicts interpretation and memory. Next, James Antony will present on (1) how causal structure among events influences recall organization in a nonlinear narrative, and (2) how the brain transitions during different event boundary types and reactivates prior neural states according to their causal structure. Finally, Janice Chen will show (1) how causal and semantic structure among events influences recall performance and its underlying neural substrates and (2) how human agency in a choose-your-own-adventure story affects the influence of these factors. Altogether, these synergistic approaches make substantial inroads into how the brain creates structure by loading and unloading neural states.

Presentations

People as anchors for event representations and memories

Zachariah Reagh¹; ¹Washington University in St. Louis

Despite the complex and continuous nature of everyday experiences, people tend to represent and remember those experiences as structured events. We can derive event structure from many different sources of information. Given that humans are social creatures, one potentially powerful source of information is that of people. However, the way in which the brain represents people and their significance, and the way this affects our memories is not clear. Here, I will present recent studies weighing in on this issue. First, I will describe an fMRI study demonstrating that anterior-temporal regions of the default mode network stably represent individual people across multiple events. I will then discuss another fMRI study revealing that these anterior-temporal default mode regions carry information about characters and relationships between those characters across an extended narrative. Finally, I will present behavioral evidence that characters in extended narratives serve as anchors, leading participants to “jump” across distant events, distorting the original narrative timeline in service of memory. Together, this set of findings indicates the importance of people in shaping our representations and memories of complex experiences.

Shared and individual encoding mechanisms for making sense of complex narratives

Emily Finn¹; ¹Dartmouth College

Although we must experience our lives chronologically, storytellers often manipulate the order in which they relay events. Furthermore, although neural and behavioral event segmentation show a degree of inter-subject consistency, meaningful individual variability exists atop these shared patterns. How does the brain support shared and/or individual-level processes for making sense of complex narratives during encoding? In this talk, I will cover two studies, one aimed at uncovering a group-level mechanism for encoding nonlinear narratives (i.e., those told out of order) and the second aimed at investigating individual differences in online event segmentation. In the first study, we found that when processing non-chronological narrative information, the precuneus and posterior cingulate engage in on-the-fly temporal unscrambling to represent information chronologically; we suggest that this unscrambling may support our ability to embed the causal structure of events in a mental situation model. In the second study, using four ambiguous short films, we found that across-subject alignment of neural event boundaries followed a posterior-to-anterior gradient that was tightly correlated with the rate of segmentation: slower-segmenting regions that integrate information over longer time periods showed more individual variability in their boundary locations. Furthermore, this variability was behaviorally significant in that similarity of neural boundary locations during movie-watching predicted similarity in how the movie was ultimately remembered and appraised.

Behavioral and neural effects of causal structure bridging across experiences

James Antony¹; ¹California Polytechnic State University, San Luis Obispo

While recounting experiences, one can transition between events via multiple forms of stimulus structure, including nearby events in time (temporal), similar events (semantic), or events influenced by the current event (causal). Here, I will discuss two experiments disentangling the behavioral and neural consequences of these factors. In a first experiment, participants watched the non-linear narrative, Memento, under different task instructions. For each scene, I computed semantic and causal networks, after which I contrasted the evidence for temporal, semantic, and causal recall strategies. Critically, there was stronger evidence for the causal than semantic or temporal strategies – even after asking participants to perform recall in the presented order. In a second, fMRI experiment, participants watched and recalled a TV show featuring five temporally interleaved storylines. Notably, some transitions across storylines featured spatiotemporal changes (ST), while others were storyline only (SO) (i.e., the conversation topic changed within-scene). Behaviorally, causal structure again significantly influenced recall organization. Neurally, boundary responses substantially differed across the brain between ST and SO transitions. Additionally, using greedy state boundary search, a (visual) control region showed neural event boundaries only at ST transitions, whereas the angular gyrus had boundaries in both cases. Moreover, pattern similarity analyses revealed that the angular gyrus was more similar for scenes within versus across storylines (while controlling for time), suggesting it supports mental bridging across temporal gaps. In sum, these findings highlight the importance of accounting for complex, causal networks – and their underlying neural substrates – in scaffolding knowledge building and organizing recall.

Causality and agency in memory for natural events

Janice Chen¹; ¹Johns Hopkins University

What will you remember from this day? Some details and moments of our experiences are forgotten or never encoded, while others are retained in memory for minutes, days, or even years. I will first describe experiments showing how the causal and semantic structure of experiences -- the network of causal and semantic connections between events in audiovisual movies -- predicts what we remember later, and how this structure is recapitulated during narrated recall. In the brain, hippocampal responses increase when event connections become more dense, and representations in default mode network areas synchronize across individuals during recall of these events. Next, I will show how causal and semantic structure's impact on memory changes when participants have agency, that is, when they choose their own path through an interactive story. Our results demonstrate that agency enhances idiosyncrasy in which details are later recalled, reduces the ability of NLP-derived semantic structure to predict memory, and increases clustering of recalled events; all three phenomena may reflect a "personalization" of semantic space when individuals have decision power over their own experience. Together, these studies reveal how event network structure and agency guide the flow of our ongoing experiences, shaping what and how we remember.