MOTOR EXPERIENCE SHAPES THE RESPONSE OF THE MIRROR NEURON SYSTEM IN CHILDREN WITH CEREBRAL PALSY

Recent findings indicate that in children with Unilateral Cerebral Palsy (UCP) the observation of actions performed by pathological models, as compared to observation of actions performed by typically developing models, determines an increased activation of the Mirror Neuron System (MNS). However, the relationship between MNS activation during observation of pathological models and individual motor ability remains still to be explored. In the present fMRI study, sixteen UCP children (aged 9 to 14 years), with mild to moderate hand impairment, performed two functional tasks: (a) observation of grasping actions executed by healthy and pathological models; (b) execution of grasping actions and simple movements using the more affected hand. Clinical assessment included measures of unimanual and bimanual motor ability. The results showed that observation of the pathological model elicited stronger activation in the main nodes of the MNS, namely ventral premotor and inferior parietal cortices, compared to observation of the healthy model. Conjunction analysis revealed shared activations of areas belonging to the MNS during the observation of the pathological model and grasping action execution, whereas no overlap emerged between observation of the healthy model and grasping execution. Importantly, premotor activity during observation of pathological vs. healthy model was negatively associated with functional scores, while parietal activation showed a positive association with these measures. These two different associations suggest that children with more severe motor impairment rely more strongly on premotor, kinematic-based simulation mechanisms, while those with better motor abilities engage parietal regions more robustly, consistent with a goal-oriented mode of action encoding.