Is bimanual interference affected in the case of a central proprioceptive loss? New insight from a left-brain-damaged single-case study

OBJECTIVE It was suggested that the bimanual coupling effect might be linked to motor intentionality and planning, which are the top-down components of motor execution. However, previous results in pathological and healthy individuals have also underlined the pivotal role of bottom-up sensorimotor information. METHOD In this single-case study, the Circles-Lines Coupling Task was administered to a left-parietal-brain-damaged individual. The cerebral lesion caused a central proprioceptive loss, relative to the impaired right hand, when out of the visual control. For the 1st time in literature, we sought to investigate whether the movement of the unaffected hand induced an efficient coupling effect on the movement of the affected one. The bimanual task was performed in the presence and absence of visual input. The patient's performance was compared with that of healthy controls. RESULTS We observed the traditional bimanual coupling effect in healthy controls. Moreover, we also replicated the effect when they performed the task blindfolded. In the case of the patient, both hands showed the typical ovalization of the line trajectory when the task was performed in visual modality. It is interesting that when the patient performed the task blindfolded, the trajectories of the impaired right hand seemed to be not influenced by the concomitant circular movement of the spared left hand. CONCLUSIONS The movement of the unaffected hand induced a bimanual coupling effect on the movement of the affected one only when the visual input was available. In absence of a visual feedback, the aberrant proprioceptive information might preclude the emerging of bimanual coupling, even in the case of a preserved motor intentionality and planning. (PsycInfo Database Record (c) 2020 APA, all rights reserved).