The control of manipulative skills and eye-hand coordination in older adults

Abstract

The ability to perform fine manipulative skills is a unique attribute of the human being and the interest in investigating manipulative motor skills in older adults is growing. The execution of manipulative tasks requires the mapping between sensory information and hand movement. Among the different sensorimotor systems, the visuomotor system plays an essential role in controlling manipulative skills, particularly in older adults. This system is involved in transforming visual information into the appropriate motor commands needed to perform the manual task efficiently. The organization and control of manipulative tasks rely on the adequate extraction of visual information, and gaze plays an essential role within this process. Although eye-hand coordination is a remarkable aspect of successful control of manipulative skills, this aspect has not been systematically investigated in older adults. Therefore, the present proposal focuses on these issues through three different studies. Study 1 aims to examine the linking of action phases and gaze behavior when learning a task involving both spatial and temporal demands in older adults. In this study, we will examine eye-hand coordination in older adults in a task in which participants will move a cursor to successively acquire visual targets, as quickly as possible, by actively keeping the cursor within the target zone (hold phase) for a required duration, before moving to the next target (transport phase). This study will allow us to investigate the skill acquisition and gaze behavior associated with such learning in older adults in a manipulative task that comprises a sequence of action phases. Skill acquisition in such tasks involves a transition from reactive control (motor commands triggered by sensory events signaling completion of the current phase) to predictive control (motor commands launched in anticipation of the actual phase completion). Examining gaze behavior in the course of skill acquisition in older adults would bring new insights about gaze control in older adults. Study 2 aims to investigate eye-hand coordination in a manipulative motor skill in which a cognitive task is used to compete for gaze in older adults. The use of competition for gaze may reveal the most critical functions of gaze in manual action. That is, because of the need to perform two tasks simultaneously, gaze will be directed to the manual task only when it is most necessary to complete the task successfully. The participants will reach for and grasp a marble, and then insert it in a slot using their dominant hand. There will be a stand with three slots, and the slot to insert the marble will be cued by a light located next to the slot. The appearance of the light cue will indicate the beginning of the task. The participants will simultaneously monitor a string of letters (Cs and Us) presented on a screen in front of them while performing the marble fitting task. They will press a button with the non-dominant hand when they see an occasional U in the screen. Study 3 aims to examine competition for gaze in a manipulative task in which two motor tasks will be performed simultaneously in older adults. Study 3 is an extension of Study 2, and it will examine eye-hand coordination when competition for gaze comes from performing two simultaneous motor tasks. In this study, a second stand (with slots and marble) will be used, and the participants will complete the task with both hands at the same time. Of particular interest is whether the older adults will move the two hands asynchronously, which may reduce the competition for gaze at crucial time points during the evolving task. This series of studies will provide new insights about eye-hand coordination in older adults, which is an essential component of several activities of daily living. (AU)