Deciphering key factors contributing to age-related decline in visuomotor tracking through the manipulation of target refresh rate and gaze contingency

The ability to continuously adjust hand movements using visual information is critical for success in many everyday tasks. To further characterize the age-related decline in visuomotor processes, here we investigated a task in which participants had to track with the hand, by means of a joystick, a visual target whose position was updated at different rates on a screen (from 1.5 to 240 Hz). This procedure was selected to grade the necessity for online control. As the target refresh rate increased, the need to continuously update hand motor commands became greater. We also manipulated gaze contingency and asked participants to perform this tracking task under gaze-free and gaze-fixed conditions, a procedure chosen to assess the contribution of eye movements and peripheral vision. The comparison between 30 older (71 yrs, 17 females) and 28 younger (21 yrs, 17 females) participants revealed detrimental effects of aging on tracking accuracy, notably through greater mean cursor-target distance and lag. Importantly, temporally realigning hand and target signals did not erase the gap in tracking performance between young and older participants. Moreover, we noticed that the effect of age was greater under higher target refresh rates and gaze-free conditions. Finally, sex/gender differences were found in each age group with men generally outperforming women. Overall, we interpret these observations as evidence that the age-related decline in manual tracking is driven by both slower and less accurate visuomotor loops, particularly when eye movements are engaged.