1 2 3 4 5 6 Motor Learning and its Sensory Effects : The Time Course of Perceptual Change , 7 and its Presence with Gradual Introduction of Load 8 9 10 11 12

22 A complex interplay has been demonstrated between motor and sensory systems. We 23 have recently shown that motor learning leads to changes in the sensed position of the 24 limb (Ostry et al. 2010). Here, we document further the links between motor learning and 25 changes in somatosensory perception. To study motor learning, we used a force field 26 paradigm in which subjects learn to compensate for forces applied to the hand by a 27 robotic device. We used a task in which subjects judge lateral displacements of the hand 28 to study somatosensory perception. In a first experiment, we divided the motor learning 29 task into incremental phases, and tracked sensory perception throughout. We found that 30 changes in perception occurred at a slower rate than changes in motor performance. A 31 second experiment tested whether awareness of the motor learning process is 32 necessary for perceptual change. In this experiment, subjects were exposed to a force 33 field that grew gradually in strength. We found that the shift in sensory perception 34 occurred even when awareness of motor learning was reduced. These experiments 35 argue for a link between motor learning and changes in somatosensory perception, and 36 they are consistent with the idea that motor learning drives sensory change. 37 38