Interplay of compensation and true recovery in upper limb movements post-stroke: a computational model

Personalized technology-assisted neurorehabilitation should rely on understanding the mechanisms of spontaneous recovery. We describe a minimal model of neural control of arm movements and neuromotor recovery, consisting of an optimal feedback controller, responsible for generating the motor command, and a corticospinal model, responsible for transferring the motor command to the muscles. Impairment is described as a lack or reduced gain in specific corticospinal pathways. Recovery is modeled as the interplay between restitution or true recovery - through the reorganization of the spared cortico-spinal connectivity, mediated by a form of use-dependent plasticity - and compensation - determining the high-level commands that lead to movements that maximize the desired payoff by minimizing the effect of impairment.True recovery relies on the amount of activation of the impaired actuators. Compensatory strategies emerge as a consequence of adaptation of the internal model of the body to incorporate the impairment.Clinical relevance Modeling the mechanisms underlying recovery after brain injury may provide insights for developing patient digital twins, which can be embedded in robot controllers to allow for personalized rehabilitation.