AbstractLimb disuse has overt substantial measurable maladaptive consequences, which are reinforced during the sleep consolidation process, hence highlighting that a continuous stream of sensory inputs and motor outputs are necessary for the maintenance of intact brain organization. Motor Imagery (MI), which corresponds to the mental representation of movement without its actual execution, is known to significantly activate motor networks, even when overt movement are no longer possible.

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... MI might rapidly compensate the maladaptive neuroplasticity elicited by immobilization remains however a working hypothesis, which has received far less attention. Here, we investigated the potential benefits of MI practice during 12 hr of unilateral arm-immobilization on the sensorimotor and cortical representations of the arms, as well as during subsequent sleep. Using a within-subject design, fourteen participants were first tested after a normal day of motor activity (without immobilization, NoImmo), followed by two randomized 12 hr conditions separated by 1 week, whereby their right (dominant) arm was immobilized either with MI practice 15 min every two hours (ImMI), or without MI (ImCtrl). After each daytime condition, participants were tested on a hand laterality judgment task to assess changes in the sensorimotor representation of the hands, followed by the measure of cortical excitability over both primary motor cortices (M1). Polysomnography recordings were also monitored overnight to investigate the sleep-related consolidation effects. Data revealed that MI practice prevented i) the slow-down in the sensorimotor representation of hands, ii) the cortical excitability depression over the M1 contralateral to arm-immobilization, iii) the sleep spindles reduction over both M1s, and iv) extended the time spent in REM sleep. Altogether, these results provide strong evidence that implementing MI within the context of limb-immobilization contributes to substantially limit the deleterious effect of disuse, and may further promote recovery of motor function.HighlightsMI prevents impaired sensorimotor representation caused by immobilizationM1 excitability contralateral to immobilization is preserved with mental practiceREM sleep duration is prolonged following MI practiceThe impact of immobilization on spindles occurrence over both M1s is counteracted by MI practice