Age-related preservation of proprioception- and vision-guided virtual hand movements

Our ability to sense self-movement is a proprioceptive ability that is often overlooked. Without proprioception, a mundane task like reaching for a water bottle can become challenging, especially when out of sight. With a goal of studying interactions between vision and proprioception, we recently developed a virtual reality (VR) approach that can quickly and precisely measure reaching behavior, and empirically isolate proprioceptive function (Isenstein et. al., 2022). In the present work, we aimed to elucidate the effects of age on reaching behavior and proprioception. We compared healthy older adults (ages 58-74; N = 30) to young adults (ages 18-28; N = 37) using the aforementioned VR reaching task. The task was to simply reach out forward to “touch” a virtual ball. Critically, the subject’s hand was either visible (rendered in VR) or invisible; a manipulation used to isolate proprioception. Based on previous research, we hypothesized that older adults would make less accurate reaches, especially when proprioception was isolated. However, our results showed no difference in performance between age groups in either visual- or proprioception-guided reaching (main effect of age: p = 0.058; main effect of removing vision: p < 0.001; interaction: p = 0.228). Notably, the marginal effect of age reflected numerically better performance in older adults. This finding cannot be explained by group differences in speed/accuracy (similar reaching times; p = 0.41) or differences in data quality (split-half reliability > 0.97 and > 0.93 for older and younger adults). This finding reveals a preservation of upper limb proprioception in older adults. To further investigate what other types of experience may affect proprioception-guided reaching, our ongoing work is now focusing on schizophrenia. Schizophrenia has been associated with impairments in visual perception and motor function, along with accelerated brain aging, motivating our aim to determine their relative contribution to reaching behavior.