Motor imagery in spinal cord injury patients: moving makes the difference.

Both real actions control and execution and motor imagery abilities require knowledge of the spatial location of body parts, in other words efference copy information and feedbacks from the sensory system (Frith, Blakemore, & Wolpert, 2000). Spinal cord injuries induce severe motor disability, due to a damage of the descending motor pathways (Cramer, Orr, Cohen, & Lacourse, 2007). Patients' motor imagery competences are variably reported either normal or defective (Decety & Boisson, 1990; Lacourse, Cohen, Lawrence, & Romero, 1999). We explored biomechanical constraints effects in SCI patients, as they are considered the most reliable indexes of motor imagery abilities (Parsons, 1987b). Sixteen spinal cord injuries patients and 16 neurologically unimpaired subjects have been administered with (i) the Hand Laterality Task, in which subjects were asked to judge the laterality of a rotated hand and (ii) the Mirror Letter Discrimination Task, in which subjects were asked to judge if a rotated character was in its correct upright position or mirror-reversed form. Our patients did not present the effect of stimulus orientation neither they showed any effect related to biomechanical constraints. Basing on these data, the hypothesis is that SCI patients' performance may be ascribed to the use of a different strategy to solve the tasks, based on memory rather than on mental rotation.