Visibility manipulations affect the functional connectivity related to illusory body ownership

The rubber hand illusion is a multisensory phenomenon where congruent visual and tactile stimulation induces ownership over a visible dummy hand. Manipulating visual inputs during the RHI experimental procedure may affect the strength of the illusion and alter the activation of relevant brain regions. This suggests that visual input modifications could influence the normal interconnectivity among brain regions. To test this hypothesis, we used functional magnetic resonance imaging (fMRI) data from 45 neurotypical adults to assess how functional connectivity (FC) was influenced by changes in the visibility of a virtual hand during the visuo-tactile stimulation related to a virtual hand illusion (VHI). The visibility manipulations concerned only the virtual hand, not the entire visual scene, and were accomplished through video editing. Tactile stimulation was administered by an MRI-compatible robot capable of delivering precise, repeatable stroking patterns on the participant's hand. Visibility and visuo-tactile congruence modulated FC between occipital, sensorimotor, and default mode regions. FC between these regions also modulated with the time phase of VHI induction. These findings suggest that reducing visibility of the virtual hand shifted the balance between vision and touch in the mental representation of the body, especially in later stages of visuo-tactile stimulation. Revealing that altered hand visibility dynamically modulates the FC related to multisensory integration during the VHI, our study underscores the critical role of visual input in shaping body representation.