Multisensory integration and behavioral stability.

Information coming from multiple senses, as compared to a single one, typically enhances our performance. The multisensory improvement has been extensively examined in perception studies, as well as in tasks involving a motor response like a simple reaction time. However, how this effect extends to more complex behavior, typically involving the coordination of movements, such as bimanual coordination or walking, is still unclear. A critical element in achieving motor coordination in complex behavior is its stability. Reaching a stable state in the coordination pattern allows to sustain complex behavior over time (e.g., without interruption or negative consequences, like falling). This study focuses on the relation between stability in the coordination of movement patterns, like walking, and multisensory improvement. Participants walk with unimodal and audio-tactile metronomes presented either at their preferred rate or at a slower walking rate, the instruction being to synchronize their steps to the metronomes. Walking at a slower rate makes gait more variable than walking at the preferred rate. Interestingly however, the multimodal stimuli enhance the stability of motor coordination but only in the slower condition. Thus, the reduced stability of the coordination pattern (at a slower gait rate) prompts the sensorimotor system to capitalize on multimodal stimulation. These findings provide evidence of a new link between multisensory improvement and behavioral stability, in the context of ecological sensorimotor task.