The sensory-motor overlap in motor imitation: evidence from motor imagery

Motor imitation is crucial for acquiring motor skills and social cognition, yet the theoretical understanding of its underlying mechanism remains partial. The direct matching hypothesis suggests that the overlap between observed and executed motions is crucial for effective motor imitation. This study aimed to investigate the behavioral benefits of motor imitation, and to validate its theoretical basis by examining its brain activation pattern during motor imagery. We recruited 56 college students and compared their motor proficiency and imagery quality after different learning strategies. Participants were randomly assigned to observation, observation with disturbance, imitation, or control groups. The observation with disturbance group was designed as a sensory-motor conflict condition to contrast with imitation where the sensory and motor representations aligned. The results showed that both motor imitation and observation enhanced motor proficiency with only imitation outperforming control group, and only imitation improved imagery quality. The functional near-infrared spectroscopy (fNIRS) analysis revealed a significant increase in the primary somatosensory cortex activation following imitation, and a contrasting change pattern following observation with disturbance. The fNIRS results highlighted the necessity of sensory-motor overlap for effective motor imitation. These findings confirmed that motor imitation was an optimal strategy for motor learning, with the primary somatosensory cortex as the key neural substrate, and validated the direct matching hypothesis.