Voluntary modification of rapid tactile-motor responses during reaching differs from its visuo-motor counterpart

People commonly hold and manipulate a variety of objects in everyday life, and these objects have different physical properties. In order to successfully control this wide range of objects, people must associate new patterns of tactile stimuli with appropriate motor outputs. We performed a series of experiments investigating the extent to which people can voluntarily modify tactile-motor associations in the context of a rapid tactile-motor response guiding the hand to a moving target (previously described in Pruszynski et al. 2016) by using an anti-reach paradigm in which participants were instructed to move their hands in the opposite direction of a target jump. We compared performance to that observed when people make visually guided reaches to a moving target (cf. Day & Lyon 2000, Pisella et al. 2000). When participants had visual feedback, motor responses during the anti-reach task showed early automatic responses toward the moving target before voluntary modification to move in the instructed direction. When the same participants had only tactile feedback, however, they were able to suppress this early phase of the motor response, which occurs less than 100 ms after the target jump. Our results indicate that, while the tactile motor and visual motor systems both support rapid responses that appear similar under some conditions, these responses show sharp distinctions in terms of their malleability.