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Introduction: For people who have had a stroke, recovering upper-limb function is a barrier to independence. When movement is difficult, mental practice can be used to complement physical therapy. In this within-participants study we investigated the effects of combined action observation and motor imagery (AO + MI) therapy on upper-limb recovery in chronic stroke survivors. Methods: A Graeco-Latin Square design was used to counterbalance four mental practice conditions (AO + MI, AO, MI, Control) across four cup-stacking tasks of increasing complexity. Once a week, for five consecutive weeks, participants (n = 10) performed 16 mental practice trials under each condition. Each trial displayed a 1st person perspective of a cup-stacking task performed by an experienced model. For AO, participants watched each video and responded to an occasional color cue. For MI, participants imagined the effort and sensation of performing the action; cued by a series of still-images. For combined AO + MI, participants observed a video of the action while they simultaneously imagined performing the same action in real-time. At three time points (baseline; post-test; two-week retention test) participants physically executed the three mentally practiced cup-stacking tasks, plus a fourth unpractised sequence (Control), as quickly and accurately as possible. Results: Mean movement execution times were significantly reduced overall in the post-test and the retention test compared to baseline. At retention, movement execution times were significantly shorter for combined AO + MI compared to both MI and the Control. Individual participants reported clinically important changes in quality of life (Stroke Impact Scale) and positive qualitative experiences of AO + MI (social validation). Discussion: These results indicate that when physical practice is unsuitable, combined AO + MI therapy could offer an effective adjunct for neurorehabilitation in chronic stroke survivors.

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Children with developmental coordination disorder (DCD) exhibit deficits both in imitation and motor imagery (MI) compared to typically developing children. Combined action observation and motor imagery (AO + MI) instructions can however enhance automatic imitation in both groups. In the present study we investigated the effects of AO + MI instructions on intentional imitation in children both with (n = 13) and without DCD (n = 12). On each trial participants observed and/or imagined before executing a familiar rhythmical pantomime action. These target actions were either habitually fast (tooth brushing or window wiping) or habitually slow (paint brushing or face washing), in the vertical or horizontal plane. Within each habitual speed, the target action speed was subtly manipulated across trials (fast vs. slow). Instruction condition was manipulated across three blocks of 16 trials: (1) observe before imitating the target action; (2) observe then imagine the action before imitating; (3) observe while imagining the same action before imitating (AO + MI). Kinematic analyses revealed typically developing children imitated the observed cycle times significantly better than children with DCD. A main effect of instruction showed imitation improved for AO + MI compared to the other two instructions. Within-group analyses found a significant advantage in DCD for AO + MI compared to observe then imagine. In typically developing children, imitation was significantly enhanced for AO + MI compared to observe then imitate. Combined AO + MI instructions therefore represent a promising new approach to refining performance of everyday rhythmical actions in children both with and without DCD, with implications for movement therapy and sports training.

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RESUMEN

Developmental coordination disorder (DCD) is a neurodevelopmental condition characterized by uncoordinated movement relative to age. While action observation (AO) and motor imagery (MI) can both independently enhance movement skills in children, we report the first study to assess the effects of combined action observation and motor imagery (AO + MI) on automatic imitation in children aged 7-12 years both with DCD (n = 12) and without DCD (n = 12). On each trial, participants planned to execute an instructed rhythmical action (face washing or paint brushing). Before responding, participants observed a rhythmical distractor showing the same or a different action with a subtle speed manipulation across trials (fast vs. slow). Automatic imitation was quantified as an imitation bias in subsequent response cycle times. Across blocks of trials, participants engaged in AO, MI, or combined AO + MI during the distractor phase or intentionally imitated the distractor speeds. Although there were no between groups differences, combined AO + MI instructions produced a significantly greater imitation bias (115%) than both AO (109%) and MI (109%), with intentional imitation yielding the strongest effects overall (128%). Within groups analyses revealed a significant bias for AO and MI in both groups. Combined AO + MI effects were significantly greater than AO in typically developing children and were greater than both AO and MI in children with DCD. These results demonstrate a clear capacity for different forms of motor simulation in children both with and without DCD. Moreover, combined AO + MI instructions represent an advantageous method for training movements in children with different motor abilities compared with separate AO and MI instructions.

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