The confusing role of visual motion detection acuity in postural stability in young and older adults

Background: Vision is commonly reported to play a crucial role in postural control and even more so in advancing age. Among its functions, visual motion perception provides the brain with information about self-motion and the motion of the surrounding environment. Objectives: To clarify the nature of the relationship between visual motion acuity and postural control and its modulation with age. Methods: 66 healthy participants took part in the study. They were divided into two groups: a younger group of 32 participants (15 females) with a mean age of 25.5 years (SD = 2.9), and 34 healthy older participants (18 females; 72.1 +/- 6.0 years). Participants completed a visual motion detection test (VMDT) that assessed the minimal speed of Gabor patch that could be detected. Following, participants stood on a force plate in 4 conditions, either with eyes open or closed and standing on either a hard surface or foam. Their stability was assessed by the mean velocity of their center of pressure. Results: Younger participants exhibited better visual motion acuity (p = 0.0097) and better postural performance across all conditions (p < 0.0001), and were less affected by the increase in task complexity compared to older participants. Furthermore, a linear mixed-effects model revealed a significant influence of visual motion acuity on postural performance (p = 0.032). This association was modulated by the condition (p = 0.047), and showed a trend of modulation by the age group (p = 0.066). Pearson's analysis revealed a positive association between visual motion acuity and postural stability in young but not in older individuals in all conditions. Conclusion: Our findings suggest that visual motion acuity, assessed using VMDT, is linked to stability even with eyes closed. This connection could be explained by light transmission through the eyelids or by the presence of a confounding variable such as visuo-spatial attention, which is known to decrease with aging.