Lu-Chun Yeh¹ (), Marius V. Peelen², Daniel Kaiser^1,3; ¹Justus Liebig University Gießen, Germany, ²Donders Institute for Brain, Cognition and Behaviour, Radboud University, The Netherland, ³Center for Mind, Brain and Behavior (CMBB), Philipps University Marburg, Justus Liebig University Gießen, and Technical University Darmstadt, Germany

In real-world scenes, objects reliably appear alongside other objects (e.g., pots, forks, mugs, and food can all be found in the kitchen). Prior fMRI work suggests that object representations in the parahippocampal place area are organized by such co-occurrence statistics among objects. However, it remains unclear when these representations emerge, whether they differ from other representational dimensions (e.g., category), and whether they reflect a mutual priming between co-occurring objects or the activation of shared scene representations. To investigate these questions, we conducted an EEG experiment where participants viewed individual objects while performing a one-back task. We orthogonally manipulated the objects’ co-occurrence context (kitchen vs. garden) and category (tool vs. non-tool), and matched their overall shape across the contexts and categories. To characterize the time course of representations related to co-occurrence and category, linear classifiers were trained on EEG response patterns from a subset of objects across the co-occurrence contexts or object categories and tested on an independent subset of objects. Results revealed orthogonal representations of co-occurrence and category, which both emerged during an early (co-occurrence: 116–263 ms, category: 170–255 ms) and a late (co-occurrence: 368–467 ms, category: 274–499 ms) time window. To examine whether representations of co-occurrence are driven by the activation of common scene representations, we trained classifiers on EEG response patterns evoked by kitchens and gardens (obtained in separate runs) and tested them on response patterns evoked by objects associated with the two contexts. Accurate cross-classification from 360–499 ms suggested that late representations of object co-occurrence are indeed driven by the activation of the associated scene context, while earlier representations likely reflect a co-activation of objects. Together, our findings delineate how objects are rapidly associated with one another and, in turn, their common context to facilitate behavior in typically structured environments.

Acknowledgements: LCY is supported by the MSCA programme (101149060). DK is supported by the DFG (SFB/TRR135,222641018; KA4683/5-1, 518483074, KA4683/6-1, 536053998), “The Adaptive Mind”, and an ERC Starting Grant (PEP, ERC-2022-STG 101076057).