Error correction strategies for motor behavior after unilateral brain damage: short-term motor learning processes

In order to identify the mechanisms underlying motor impairments and motor learning following stroke-related brain damage, we analyzed correction strategies used by hemiparetic individuals to produce precise elbow flexion movements of the paretic arm and compared them to those of healthy individuals. Participants made rapid elbow flexion movements to a 6 degrees wide target and were instructed to correct movement errors as quickly as possible when a spring-like load was unexpectedly introduced. Angular positions and torques before correction were used to identify error patterns. Results showed that participants with mild hemiparesis minimized movement errors within three trials, as did healthy participants. In contrast, severely affected individuals needed more trials to diminish errors and their movements were inconsistent. Participants with a moderate motor disability used both typical and atypical correction strategies. The differences in correction behaviors likely reflect deficits in arm motor function (r=0.79) and executive function (r=0.58) rather than levels of intellectual function (IQ ratings). Results indicate that the deficits that individuals with stroke experience when adapting their movements to changed load conditions may be due to difficulty in rapidly integrating visual and proprioceptive information. Deficits in executive function could also contribute to problems in producing accurate and consistent movements from trial to trial. Taken together, these results imply that all hemiparetic individuals would not benefit equally from the same motor re-training approaches.