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Alt Murphy M.1,2, Baniña M.C.2,3, Levin M.F.2,3
1Gothenburg University, Inst. Neuroscience and Physiology, Rehabilitation Medicine, Gothenburg, Sweden, 2McGill University, Center for Interdisciplinary Research in Rehabilitation (CRIR), Montreal, Canada, 3McGill University, School of Physical and Occupational Therapy, Montreal, Canada
Background: Contextual constraints, such as object properties, object location with respect to the body and object affordances, impact motor planning and execution. In healthy young adults, movements are planned beyond the first phase of the task and the initial grasp position on the object is modulated based on the final goal of the task. This perceptuo-motor coupling has been described as the end-state comfort (ESC) effect. How these aspects of motor control are influenced by perceptual or motor deficits after stroke is, however, largely unknown.
Purpose: This study aimed to determine the extent to which visuo-perceptual and motor deficits due to stroke impact the ESC, specifically the grasp height effect.
Methods: Thirty-four older adults (17 controls, 17 chronic stroke) performed a functional goal-directed two sequence task with each arm, consisting of reaching and transporting a cylindrical object (a plunger) from a standard height to 4 different target heights. Kinematics of the arm and trunk were recorded and Fugl-Meyer Motor Assessment and Motor free Visual Perception Test scored. Mixed model analysis was used to determine the ESC effect.
Results: The ESC, studied as grasp height effect, was present to some degree among all participants, but the extent of this effect was decreased in those with visuo-perceptual deficits due to stroke, regardless of the side tested. Sensorimotor impairments alone, also confirmed with changed kinematics, in individuals with stroke did not to influence the grasp height effect to a large extent compared to controls.
Conclusion(s): Perceptuo-motor coupling, expressed as the grasp height effect, is decreased in individuals with visuo-perceptual deficits due to stroke, but not in those with sensorimotor deficits alone. Increased knowledge of the impact of visuo-perceptual deficits on movement planning and execution may assist clinicians in selecting more effective treatment strategies to improve perceptuo-motor skills and enhance motor recovery.
Implications: The results of this study suggest that in clinical settings, practice should include tasks that require planning over two steps, in order to facilitate improvement of perceptuo-motor skills. Furthermore, to develop the ability to modulate the grasp according to object affordances, practice with different locations in the arm workspace within a training session is recommended.
Funding acknowledgements: Project was supported by Swedish Brain Foundation (MAM) and Canada Research Chairs in Motor Recovery and Rehabilitation (MFL).
Topic: Neurology: stroke
Ethics approval: The study protocol was approved by the Centre for Interdisciplinary Research in Rehabilitation of Great Montreal (CRIR), Canada.
All authors, affiliations and abstracts have been published as submitted.
