Motor imagery development and proprioceptive integration: Which sensory reweighting during childhood?

It is widely accepted that motor imagery development during childhood may be due to refinement of internal models of action. At the same time, gradual improvement of predictive motor control in children may reflect an increasing ability to integrate the proprioceptive afferences with other sources of sensory information (especially vision). The current study investigated the extent to which motor imagery refinement observed between 5 and 9 years of age was related to the increasing ability to integrate proprioceptive afferences with vision and audition signals. To attain this goal, we compared motor imagery performances of 96 children (32 5-year-olds, 32 7-year-olds, and 32 9-year-olds) who received either visual and auditory inputs (VA condition) or visual, auditory, and proprioceptive inputs (VAP condition) during the imagery task. Motor imagery capacity was evaluated by means of mental chronometry paradigm based on a walking task. Our results revealed that correlations between overt and covert movements gradually increased across age in either the VA or VAP condition. Most important, in 5- and 7-year-olds, covert walking times were significantly longer than overt walking times in the VAP condition, whereas covert walking times were not different from actual walking times in the VA condition. In 9-year-olds, covert walking times were not different from overt walking times in either the VAP or VA condition. We suggest that motor imagery refinement during childhood can be partially related to the ability to integrate proprioceptive inputs with other sources of sensory information. Furthermore, our results shed light on the sensory content of motor images in children.