Visual motion adaptation induces a tactile motion after effect
Konkle, Wang, Hayward, & Moore
Touch and vision provide information from a common external reality, suggesting they may share common neural representations of stimulus features such as motion. Indeed, there is increasing evidence that tactile input drives 'visual' areas in normally sighted individuals, including the MT+ complex, the lateral occipital complex, and V1. To the extent that these shared networks support conscious perception, adaptation in one modality is predicted to impact perception of the other.
During visual motion adaptation, observing one direction of motion for a sustained period subsequently causes a static visual stimulus to appear to move in the opposite direction, the 'motion after effect'. In a first experiment, tactile motion sweeps were presented to the fingertip using a novel 6x10 array of independently driven stimulators. Rows of vibration were sequentially presented at 5-80 mm/s, creating a percept of apparent motion over the fingertip in a single direction. Following 20s of motion, a tactile 'bar' (vibrating row) was presented for 1s, and observers reported the perceived direction. Opposite motion was perceived on ~80% of the trials when velocities exceeded 10 mm/s (N=8 subjects). To test the prediction that cross-modal transfer should occur, visual drifting gratings (0.5 cpd) were presented on a computer screen in front of the visible fingertip while a single non-moving collinear tactile bar was presented at the same rate. Following 20s, the visual display was removed and the same tactile bar presented for 1s, and subjects reported the direction of perceived bar motion and provided a confidence rating. On the high confidence trials, the opposite direction of tactile motion was perceived on ~80% of trials. On low confidence trials, the illusion rate was ~65%. This after effect was not observed in control conditions when a bistable visual grating or no visual stimulation was presented (N=8 subjects).
These data reveal a robust cross-modal transfer of motion after effects from vision to touch, consistent with the prediction that neural dynamics recruited through one modality impact perception in either modality through the shared neural representations.
Konkle, T., Wang, Q., Hayward, V., & Moore, C. I. Visual motion adaptation induces a tactile motion after effect. Program No. 662.6. 2007 Neuroscience Meeting Planner. San Diego, CA: Society for Neuroscience, 2007. Online.