Contextual Role Modulates Object Representational Geometry in the Human Brain

Abstract

The human brain represents objects in a way that is both invariant across instances and flexible enough to support different contexts and tasks. Yet it remains unknown how object representations are dynamically remapped as the same object shifts across contextual roles. Using fMRI during naturalistic movie viewing we investigated how the same objects are represented when they are passive scene elements versus targets of goal-directed actions. Action targets engaged a parietal action network centered in the supramarginal and postcentral gyri, while passive objects recruited a distributed occipito-temporal network involved in visual object recognition. Within context-selective networks, representational geometry showed a double dissociation: target objects were organized by action affordance and hand posture affordance dimensions, while passive objects aligned with semantic dimensions. Visual representational structure was invariant to context. Outside these networks, representational content retained invariance, indicating that flexibility and invariance operate at different levels of the same representational system. These findings demonstrate neural remapping of object representations depending on moment-to-moment changes in contextual roles during a naturalistic scene.