Advancing the understanding of fundamental principles of motor control.

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The proposed theory-driven research program is built on our earlier achievements under the tenure of previous NSERC grants (see Feldman 2015, book): (1) The corticospinal (CS) system originating from the primary motor cortex (M1) sets and resets, in a feedforward way, the threshold (referent) position of body segments at which appropriate muscles begin to be recruited (Raptis et al. 2010; Ilmane et al. 2013; Zhang et al. 2017); (2) Threshold position control mediated by CS pathways underlies anticipatory actions (Turpin et al. 2016; Zhang et al. 2017); (3) The theory has been generalized and validated for reaching, jumping, walking in humans and head motion in monkeys (Feldman 2015); (4) It was further extended to consider higher brain functions ? the origin of directional tuning of M1 neurons (Feldman, invited review, appended) and perception, with explanations of the phantom limb phenomenon and visual space constancy (Feldman 2016). The long-term objective of the program is to further advance understanding of basic principles underlying the control of motor actions. The first specific objective is to test the hypothesis that by shifting spatial thresholds for muscle activation, the nervous system transfers balance and stability from one place to another. By doing so, the system can elicit a single step and continuous locomotion at a desired speed. In response to a transient perturbation, the system may be forced to temporarily decrease the rate of shifts in the referent body location such that the whole gait pattern will be shifted in time, a phenomenon called long-lasting ("permanent") phase resetting. We will test whether vestibular, corticospinal and/or visual systems are responsible for such phase resetting and thus involved in the control of gait speed. Testing will be done by applying Transcranial Magnetic stimulation (TMS), Galvanic Vestibular Stimulation (GVS) or visual perturbations, respectively. The second specific objective is to test the role of the ipsilateral CS tract in the control of spatial thresholds during uni- and bi-manual movements, which will help advance the theory beyond its present point, thus meeting the long-term objective. The uniqueness of this program is that it represents cutting-edge research in the further development and testing of the empirical (non-computational) threshold position control theory in comparison to the alternative, computational theory of motor control in the hope that the controversy between them will eventually be resolved. This multidisciplinary program will benefit the training of HQP by substantially contributing to the understanding of how biological movements are controlled. The applied aspect of this program can also be significant as has been demonstrated by our team by elaborating a device for identification of post-stroke spasticity (patented) and by the use of the physiological principles of referent control in improving human-like motions of robots (e.g. Bicchi et al. 2002).