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George E. Carvell, PhD, PT   University of Pittsburgh
 
DISTRIBUTED MOTOR CONTROL: Reaching and Grasping
Corticocortical inputs to Premotor Areas PMd & PMv arise from different portions of the posterior parietal cortex. The two parietal areas have separate streams of visual inputs. This provides parallel pathways for two visuomotor tasks: Reaching and Grasping.
MOTOR CONTROL REQUIRES A DISTRIBUTED SYSTEM WITH TASK- RELATED PARALLEL PATHWAYS
KS&J
Fig 38-20, p 775
Reaching to grasp an object results in a nearly linear motion path (solid line fig 7.3 ) and a continuous ‘programmed’ movement profile having a single velocity peak (typical of well rehearsed motor tasks) as shown by dashed line fig 7.3. The finger aperture changes as the hand approaches the object, I.e., grasp and reach are controlled simultaneously, not sequentially. Depending on the size and other physical characteristics of the object, we alter the opening aperture of the fingers and the motion profile of the hand in space in a feed-forward manner.
CONTROL OF REACH AND GRASP GO “HAND IN HAND”
GMOMM  © 2001
Hand Motion
Kinematics
Finger Opening During Reach
(20 msec between dots)
Brooks fig 7.3 p 133