Effects of expertise and age on reaching movements guided by vision, memory and proprioception.

Our ability to effortlessly sense our self-movement in space is a proprioceptive ability that is often overlooked. Without proprioception, a mundane task such as walking can become a challenging task. We recently showed how virtual reality (VR) can be used to quickly and precisely measure reaching behavior and also offer easy ways to isolate effects of proprioception and memory (Isenstein et. al., 2022, Plos ONE). Here, we aimed to elucidate the effects of expertise and age on reaching behavior. The subjects’ task was to simply reach out forward to “touch” a virtual ball. Critically, the subjects’ hand was either visible (rendered in VR) or invisible; a manipulation used to isolate proprioception. To assess effects of memory, subjects reach for the target 1 second after it was made invisible. In our published work, we found a large amount of individual variability in the reaching accuracy. This motivated our hypothesis that this variability may be due to individual differences in experiences with self-movement, such as dancing. Dancers train to make precise and rhythmic movements, often without the full use of vision. Interestingly, after testing 17 dancers and 14 non-dancers, we found no significant differences in the accuracy of reaching movements guided, in separate conditions, by vision, proprioception, or memory. Next, we investigated effects of age on vision- and proprioception-guided movements in 18 older adults (ages 58-74). We found a significant correlation between age and the accuracy of proprioception-guided movements (r=0.44, p=0.032, one tailed), but not between age and visually-guided movements. This suggests that effects of age become more prominent when subjects cannot rely on vision to aid their movements. In summary, we found that dance experience does not affect the accuracy of reaching behavior. In contrast, we found that aging does affect reaching behavior, especially when vision of the movement is unavailable.