Shared multivariate brain patterns during recall associated with greater overlap in recalled information

Poster Session D - Monday, April 15, 2024, 8:00 – 10:00 am EDT, Sheraton Hall ABC

June-Kyo Kim¹ (junekyo.kim@mail.utoronto.ca), Charan Ranganath², Alexander Barnett¹; ¹University of Toronto, Department of Psychology, ²University of California, Davis, Center for Neuroscience

During encoding and recall of naturalistic events people instate shared multivariate patterns throughout higher order cortical regions of the brain. These shared patterns are thought to reflect shared mental models of the encoded and recalled events. We explored whether neural patterns are more correlated in participants who recall events more similarly to each other. Participants were scanned using fMRI as they encoded two 15-minute movies and verbally recalled those movies either immediately or after a 2-day delay. Intersubject pattern similarity (ISPS) was calculated from fMRI data for four default mode subnetworks previously shown to be connected to the hippocampus. Verbal recall was transcribed, segmented into events, and fitted to topic models. This produces a vector of “topic activations” that represents the abstract concepts present in recall for each event. We calculated how similar each participant’s recall was compared to the group by correlating the vector of topic activations for each subject, for each event to the group. Further, we manually scored each recall transcript for details using published methods. We found that topic similarity is strongly associated with recall ISPS in posterior medial, medial prefrontal and medial temporal networks, particularly at the 2-day delay. This suggests that when participants recall events similarly after a delay, their pattern of brain activation is also more similar. However, ISPS was not related to the number of details recalled suggesting that shared activation patterns between people are not simply reflective of how well something is remembered, but how similarly it is remembered to others.

Topic Area: LONG-TERM MEMORY: Episodic