Abnormal cognitive planning and movement smoothness control for a complex shoulder/elbow motor task in stroke...

Cortical function is not well understood in stroke survivors with persistent dyscoordination. The study purpose was two-fold: 1) characterize cognitive planning time and cognitive effort level for a circle-drawing motor task in stroke survivors using shoulder/elbow muscles and 2) identify the relationship between cognitive effort level and movement smoothness.

Twelve stroke survivors with shoulder/elbow coordination deficits (>12 mo) and eight controls were enrolled. The motor task was to draw a circle on a horizontal surface using only shoulder/elbow muscles. Outcome measures were: EEG-derived cognitive planning time, cognitive effort level, and movement smoothness. Comparisons between stroke and controls were made using t-tests. The Pearson's correlation model was analyzed to determine the relationship between movement smoothness and cognitive effort level.

Stroke subjects showed a statistically significant prolonged motor planning time versus controls for both lesion and non-lesion sides (p=0.013 and 0.049, respectively). They also showed a statistically significant elevated effort level versus controls for both sides (p=0.016 and 0.013). The patients exhibited statistically significant poor movement smoothness in the medial/lateral and forward/backward movement directions versus controls (p=0.035 and 0.037, respectively). For stroke, there was a significant correlation between cognitive effort level on the non-lesion side and smoothness of movement in the medial/lateral and forward/backward directions (r=0.54, p=0.036 and r=0.76, p=0.002, respectively). On the lesion side, results were mixed (r=0.268, p=0.2 r=0.59, p=0.023, respectively).

Stroke survivors with upper limb motor deficits exhibit a longer cognitive planning time and elevated cognitive effort for performance of a complex shoulder/elbow motor coordination task. The elevated cognitive effort level was associated with poor (jerky) motor performance, suggesting a potential role of the CNS in controlling movement smoothness of the arm.