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Fri, April 23

Speaker: Minos Niu (Postdoctoral Candidate)

Title: How position and velocity information from proprioception is used in controlling arm movements

Abstract: Human voluntary movements are controlled by a combination of feed-forward control and sensory feedback. Sensory feedback from muscle spindles provides velocity and position information of the ongoing movement. Previous studies have shown that proprioceptive feedback control is suppressed in the beginning of point-to-point movement, and is facilitated at the time of peak muscle torque (Shapiro, Niu et. al. 2009). Following this facilitation of proprioceptive feedback control, it is unknown how velocity information and position information are used to control the movement.  In particular, it remains a question that whether the motor system corrects velocity or position errors when the ongoing movement is disrupted.

In my PhD study, the objective is to dissociate velocity and position feedback control in arm reaching movements. The hypothesis is that the control of arm reaching movement includes an absence of proprioceptive feedback followed by an interval of velocity feedback control, and then an interval of position feedback control. We experimentally tested this hypothesis by perturbing the movement using a servo-controlled robot. The responses in muscle surface electromyograms (EMGs) to the perturbations showed that 1) no EMG response was observed in the beginning of the movement; 2)  in the middle of the movement, the response consists of a main burst that terminated when the velocity deviation diminished; 3) at the end of the movement, the amplitude of the response was proportional to the position deviation from the target. These results suggested that the proprioceptive feedback control is temporally organized as a period without feedback, followed by a velocity feedback in the middle of the movement, and finally switches to a position feedback. The rationale for this investigation is that a better understanding of proprioceptive feedback will contribute to the knowledge of how accurate movements are performed. As such, it allows movement disorders to be explained as malfunctions in proprioceptive feedback control, therefore the current study is essential for innovative treatment and assessment of movement disorders.

Host: Eric Perreault