Hemisphere specific impairments in reach-to-grasp control after stroke: effects of object size.
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.
Tretriluxana
Jarugool
J
Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, Department of Neurology, Keck School of Medicine, Los Angeles, CA 90033, USA.
Gordon
James
J
Fisher
Beth E
BE
Winstein
Carolee J
CJ
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D001132:Arm / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D004292:Dominance, Cerebral; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time; D020521:Stroke / Q000503:physiopathology*; D013647:Task Performance and Analysis; D013997:Time Factors