Effects of a Seen Hand on Visuo-Haptic Motion Processing

It has been shown that adaptation to tactile motion across the observer's hand induces a visual motion aftereffect (MAE). This crossmodal aftereffect supports the view that MAEs originate from adaptation in neural substrates underlying multisensory integration, challenging the conventional view that MAEs reflect modality-specific processing in early cortical areas. However, it is not clear how information about a seen hand influences visuo-haptic motion processing. We measured the strength of the visual MAE after visuo-haptic adaptation to the rotation of a radial grating presented with a realistic virtual hand. During the adaptation period, observers moved the arm of a force-feedback device with the right hand, and the grating and the virtual hand moved in synchrony with the observer's hand movements. We found that, after adaptation to visuo-haptic movements, the visual MAE was enhanced when the orientation of the virtual hand was aligned with the unseen observer's own hand. Our results suggest the presence of a visual motion system that is sensitive to both to visual and haptic information about one's own hand.