The various forms of sensorimotor plasticity following limb amputation and their link with rehabilitation strategies

Limb amputation is characterized by complex and intermingled brain reorganization processes combining sensorimotor deprivation induced by the loss of the limb per se, and compensatory behaviors, such as the over-use of the intact or remaining limb. While a large body of evidence documents sensorimotor representation plasticity following arm amputation, less investigations have been performed to fully understand the use-dependent plasticity phenomenon and the role of behavioral compensation in brain reorganization. In this article, I will review the findings on sensorimotor plasticity after limb amputation, focusing on these two aspects: sensorimotor deprivation and adaptive patterns of limb usage, and describe the models that attempt to link these reorganizational processes with phantom limb pain. Two main models have been proposed: the maladaptive plasticity model which states that the reorganization of the adjacent cortical territories into the representation of the missing limb is proportional to phantom pain intensity, and the persistent representation model, which rather suggests that the intensity of residual brain activity associated with phantom hand movements scales with phantom limb pain intensity. I will finally illustrate how this fundamental research helps designing new therapeutic strategies for phantom plain relief.