Modulation in the use of multisensory information during voluntary action

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As you lift a water bottle and bring it over a glass, the receptors in your muscles and eyes are exposed to different excitation patterns. Lifting the bottle first requires adjusting the initial forces generated by your limb muscles, which is known as impulse regulation. After, bringing the spout over the glass requires additional adjustments, known as limb-target regulation. Although these sensorimotor processes have been discovered through studies of visual-motor functions, little is known about the contribution of muscle receptors (i.e., proprioception) to these processes. Thus, the current research program will unravel the contribution of vision and proprioception to the impulse and limb-target regulation processes. The first series of sensorimotor studies will present brief flashes of vision at different portions of a reaching movement, while employing different movement amplitudes and durations. Building upon theoretical debates about when vision is utilized during a voluntary movement, parsimonious frameworks of the different sensorimotor processes taking place during movements of different durations and amplitudes will be developed. The second series of sensorimotor studies will add visual perturbations during the brief flashes of vision. That will include moving a cloud of random dots forming a visual background and/ or a shift in target location. Because impulse regulation is thought to occur before limb-target regulation, it is expected that background perturbations will have significant effects on limb trajectories when presented early during the movement. In turn, target jumps are expected to have significant effects on limb trajectories when presented later during the movement. The third series of sensorimotor studies will incorporate a tendon vibration manipulation that is presented between trials and reduces the sensitivity of muscle receptors (i.e., proprioception). Using selected studies from the two series above, tendon vibration studies will test for the contribution of proprioception for impulse and limb-target regulation processes. As well, when combined with visual perturbations (i.e., background and/ or target), these studies will help determine if vision and proprioception are integrated for impulse and limb-target regulation. The last series will employ perceptual reports (e.g., "Did your limb final position undershot or overshot the target?"). The influence of vision and/or proprioceptive perturbations on the perceived limb endpoint are expected to corroborate the results from the sensorimotor studies. Overall, determining which sources of sensory information predominantly contribute to impulse vs. limb-target regulation will refine models of sensorimotor control. As well, these models will inform various practical designs (e.g., human-machine interfaces, rehabilitation programs and robots, sport training protocols).