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  • Title: Hemisphere specific impairments in reach-to-grasp control after stroke: effects of object size.
    Author: Tretriluxana J, Gordon J, Fisher BE, Winstein CJ.
    Journal: Neurorehabil Neural Repair; 2009 Sep; 23(7):679-91. PubMed ID: 19411406.
    Abstract:
    BACKGROUND AND OBJECTIVE: The authors investigated hemispheric specialization for the visuomotor transformation of grasp preshaping and the coordination between transport and grasp in individuals poststroke. Based on a bilateral model, the authors hypothesized that after unilateral stroke there would be hemisphere-specific deficits revealed by the ipsilesional limb. METHODS: Right or left stroke and age- and limb-matched nondisabled participants performed rapid reach-to-grasp of 3 sized objects. The authors quantified grasp preshaping as the correlation between initial aperture velocity and peak aperture, and peak aperture and object diameter. A cross correlation analysis using transport velocity and aperture size was performed to quantify transport-grasp coordination. All statistical tests for hemisphere-specific deficits involved comparisons between each stroke group and the matched nondisabled group. RESULTS: Overall, the right stroke group, but not left stroke group, demonstrated prolonged movement time. For grasp preshaping there was a higher correlation between initial aperture velocity and peak aperture for the right stroke group and a lower correlation between peak aperture and object diameter for the left stroke group. For transport-grasp coordination the correlation between transport velocity and aperture size was higher for the left stroke group and lower for the right stroke group, which also demonstrated a higher standard deviation of time lag. CONCLUSIONS: After left stroke, there was deficient scaling of grasp preshaping and stronger transport-grasp coordination. In contrast, after right stroke, grasp preshaping began earlier and transport-grasp coordination was weaker. Together, these hemisphere-specific deficits suggest a left hemisphere specialization for the visuomotor transformation of grasp preshaping and a right hemisphere specialization for transport-grasp coordination.
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