The somatosensory side of the affordance: How seeing an object influences touch

Object perception is inherently multisensory, as the brain integrates information across sensory modalities to facilitate the interaction with them. This intrinsic 'action potential' of objects is described by the concept of affordance, which refers to the opportunities for interaction that an object offers to an organism, depending on both the object's physical characteristics and the organism's sensorimotor abilities. Converging evidence demonstrated that seeing affordable objects modulates motor activity. Coherently, viewing graspable objects can also induce a somatosensory activation associated with their tactile manipulation. Yet, little is known about the representation of affordances in the somatosensory system. Here, we investigated whether visual perception of affordable objects modulates somatosensory evoked activity. Participants viewed images of affordable and non-affordable objects, while concomitantly probing the somatosensory system with tactile stimuli delivered to both index fingers. We found that viewing graspable objects enhances somatosensory processing, as indicated by higher somatosensory evoked potentials to tactile stimuli when paired with images of affordable objects compared to non-affordable objects. These findings suggest that the observation of affordable objects triggers somatosensory responses associated with potential actions, supporting the view that object perception is a dynamic multisensory process. In everyday interactions, objects like cups are consistently grasped, leading to the formation of strong multisensory associations between objects' visual features and tactile afferences. Once well-established, these associations may allow vision alone to activate stored tactile representations, enhancing somatosensory engagement, as observed in our study.