Evidence of motor resonance in stroke patients with severe upper limb function impairments: stimuli and data
Patients with severe upper limb function impairments and matched controls were presented with videos showing grasping movements, and requested to press a key at the contact time between the hand and the object (i.e., action prediction time). In half of the trials the kinematics of the videos was kept unchanged and the object replaced with an ungraspable one. The instant in which the hand touched the object in the different videos was always the same. This experimental paradigm has proved capable of providing neurophysiological and behavioural indices of the presence of motor resonance (i.e., sub-threshold simulation of the observed action) in healthy individuals. Specifically, corticospinal activation was present only when the observed movement was suitable to grasp the object, and in the same trials the response times were more accurate (i.e., the time lag between the instant the agent touched the object and the response was shorter), an index of action prediction (Craighero et al., 2014, doi.org/10.1080/13506285.2014.904460). It is assumed that a modulation of response times in this experimental paradigm is an indirect evidence of motor resonance. All participants were asked to perform the task with both hands. Despite the serious difficulty of movement, 8 out of 18 patients were able to perform the task with their impaired hand. We found that the responses given by the paretic hand showed a modulation of the action prediction time no different from that showed by the no paretic hand, which, in turn, did not differ from that showed by the matched control participants. These results indicate that action observation involves the efferent motor system even when the hand used to respond is unable to perform the observed action due to a cortical lesion.