AbstractImplicit sensorimotor adaptation is driven by the difference between the expected and actual sensory consequences of a movement, known as a sensory prediction error (SPE). In a visuomotor rotation task, adaptation is assumed to be driven by the SPE between the rotated visual feedback and the sensory prediction based on the intended action. Via adaptation, movements shift away from the target in the opposite direction of the perturbation, thus reducing the SPE based on visual feedback. However, as a result of adaptation, an SPE resulting from the mismatch between the expected and actual proprioceptive feedback increases. Thus, one constraint on the extent of adaptation to the visual rotation may lie in how visual SPEs interact with proprioceptive SPEs (Morehead et al., 2017). As a starting point, we asked how the perceived trajectory of self-selected reaching movements is affected by the addition of proprioceptive noise. Participants (10) performed rapid reaching movements and judged whether visual cursor feedback representing fingertip position was rotated clockwise or counterclockwise with respect to their reach (Synofzik et al., 2010). We used simultaneous biceps-triceps tendon vibration during the movement to implement proprioceptive noise (Bock & Thomas, 2011). We derived estimates of discrimination sensitivity (JND) under conditions of tendon vibration and no vibration. Contrary to our expectations, all participants' JNDs improved with concurrent vibration (8.2 deg) compared to no vibration (16.5 deg). We speculate that the presence of proprioceptive noise may increase the weight given to the visual prediction, resulting in the paradoxical improvement of the JND.
Acknowledgments: Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC).