Motor imagery in conversion paralysis

Abstract

Introduction : Motor imagery was implicitly and explicitly cued in patients with conversion paralysis. Patients' explicit motor imagery of affected limbs was expected to be slowed. Methods : Six patients and six healthy controls performed an implicit mental motor rotation task (a hand and foot judgement task), an explicit mental motor rotation task, and two control reaction time (RT) tasks. Results : On the implicit task patients showed a significantly larger increase in RT per degree of rotation (RTR) than controls. There was a nonsignificant trend showing a larger RTR for the most severely affected limb in patients. This effect was stronger for the explicit hand rotation task, in which patients’ RTR was larger for the most severely affected arm. Furthermore, in 9% of the explicit hand rotation trials and in 51% of the explicit foot rotation trials patients showed a complete inability to form a mental image of their most severely affected limb. Patients were also slower on two control RT tasks. Conclusion : General slowing most explicitly manifested itself in tasks that chiefly draw on intentional operations (i.e., the explicit mental rotation task) and is strongest in the most severely affected limb. The findings suggest a general slowing of motor initiation, due to impaired functioning of explicit, intentional processes in patients with conversion paralysis.