Evidence for a sensorimotor prediction in action observation

The mirror neuron network is activated during both execution and observation of the same action, enabling visual-to-motor transformation. Two main hypotheses account for this process: the direct matching hypothesis proposes a direct link between visual cues and the observer's motor representations, whereas the predictive hypothesis suggests that motor predictions are generated and compared with visual information. We tested these hypotheses during a locomotion task. Motor prediction was assessed by comparing actual and imagined walking (forward or backward) over a 9 m path. Action observation (AO) was examined through a time-estimation inference task in which participants observed an agent walking 3 m before occlusion and estimated when the agent would reach the end of the 9 m path. We manipulated these tasks by mechanically vibrating the leg muscles, creating sensory illusions. We found that vibration-induced sensory illusions altered motor imagery timing, affecting sensorimotor prediction. Opposite effects on AO and numerical simulations supported the predictive hypothesis.