Making sense of touch: Spatial tactile cues promote efficient visuo‐somatosensory integration and restore motor accuracy under sensory conflict
Maria Evangelia Vlachou, Eva Lafaverges, Laurence Mouchnino, Jean BlouinAbstract
Effective interaction with complex environments relies on the integration of somatosensory and visual signals into coherent spatial representations of the body in external space. When these signals conflict, as during goal‐directed hand movements under mirror‐reversed visual feedback, motor performance deteriorates. Despite this conflict, the visual mapping between the hand and the environment remains preserved, and visual information typically facilitates motor performance, whereas tactile feedback impairs it. Here, we tested whether providing tactile input with explicit spatial structure renders visuo‐somatosensory integration functionally relevant and stabilizes motor behaviour under sensory conflict. Healthy adults performed a mirror‐tracing task, tracing a shape's contour with the index finger while tactile feedback conveyed either motion‐related cues alone or additional discrete spatial landmarks aligned with the outline. Spatially structured tactile cues preserved movement accuracy and smoothness relative to motion‐related tactile input, indicating more effective online motor control. EEG source analyses further revealed that, when spatial tactile cues were present, somatosensory activity increased and functional connectivity was largely restricted to sensorimotor areas. In contrast, when tactile cues did not convey spatial information, sensory conflict was associated with widespread reductions in cortical activity, including in somatosensory and parietal areas, and with a diffuse functional connectivity pattern consistent with elevated sensorimotor uncertainty. Together, these findings indicate that providing spatial structure to tactile input can mitigate the detrimental effects of visuo‐somatosensory conflict on motor performance and support more efficient integration of visual and somatosensory information during action.
Key points
Accurate movements depend on combining visual and somatosensory information to estimate the position of the body in external space. When these signals conflict, motor performance usually deteriorates and tactile feedback can become disruptive. We tested whether tactile feedback becomes useful for movement control when it provides explicit spatial landmarks, rather than only motion‐related information from finger–surface contact. During a tracing task under visuo‐somatosensory conflict, spatially structured tactile cues preserved movement accuracy and smoothness compared with when touch conveyed motion cues alone. Spatial tactile cues were associated with increased somatosensory cortical activity and a more spatially restricted pattern of functional coupling within sensorimotor networks, whereas their absence was associated with reduced somatosensory and parietal activity and a more distributed connectivity profile. Spatial structure in touch promotes multisensory integration, helping stabilize motor control under sensory conflict and highlighting how tactile cue design may improve sensorimotor function.