Advancing the understanding of fundamental principles of motor control.

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The proposed program has been built on our several major achievements under the tenure of the previous NSERC grants. (1) The discovery that the corticospinal system, rather than directly programming kinematics and motor commands to muscles, sets and resets the threshold position of body segments at which appropriate muscles begin to be recruited (Raptis et al. 2010). (2) Threshold position control mediated by corticospinal pathways underlies not only regular but also anticipatory motor actions (Sangani et al. 2011). (3) The notion of threshold position control has been generalized to multi-muscle and multi-joint control of motor actions (arm reaching, jumping, dancing, and walking in humans; Feldman et al. 2011). (4) Several classical problems in motor control has been solved, such as the posture-movement problem and the redundancy problems in multi-muscle and multi-joint control (Feldman 2011). (5)We established that weakness and spasticity in post-stroke subjects result from deficits in the central regulation of the threshold arm position and elaborated a diagnostic device to help clinicians in identifying these deficits (Patent, Feldman et al. 2006). (6) Our multidisciplinary team has developed a substantial expertise in modeling of not only single- but also whole body movements and experimentally tested predictions of these models (Pilon et al. 2005, 2006; Feldman et al. 2007; Latash et al. 2010; Gorniak et al. 2010; Yang and Feldman 2010; Feldman 2011). In the proposed program, we will analyze how the corticospinal system uses threshold position resetting to control involuntary (unloading reflex), anticipatory (self-unloading of the arm) and voluntary reaching for an object at different locations in the environment. The fundamental principles of motor control will be validated by numerical simulations of whole body movements (sit-to-stand then jump, walk and run). The program is intended to substantially contribute to the understanding of how complex movements are centrally controlled, which will be used in elaborating several devices to help clinicians in rehabilitation of post-stroke subjects with neurological deficits in the multi-muscle coordination.