eLife assessment
This valuable study extends the previous interesting work of this group to address the potentially differential control of movement and posture. Through experiments in which stroke participants used a robotic manipulandum, the authors provide evidence supporting a lack of a relation between the resting force postural bias they measure (closely related to the flexor synergy in stroke) and kinematic deficits during movement. Based on these results, the authors propose a conceptual framework that differentially weights the two main descending pathways (corticospinal tract and reticulospinal tract) for neurologically intact and stroke patients. The reviewers point out that some of the evidence supporting the authors' conclusions is incomplete, and that the study would benefit from considering alternative explanations involving other mechanisms, which could be addressed with additional experiments and analyses.