Eye-hand coordination in rapid, goal directed movements

Abstract

Background: During rapid, goal directed reaches, a saccade typically lands close to the goal of the reach. However, it is not clear how eye-hand coordination impacts endpoint precision and accuracy of both movements. Aim: We investigated whether eye-hand coordination and overall reach performance is significantly impacted by target duration and eccentricity. Method: Participants pointed rapidly to a high contrast target (white dot) that appeared at 1 of 8 different locations with equal probability. Each target was presented at a fixed eccentricity (range: 2–12°) using a block design. In separate conditions, the stimulus was displayed for 100ms, or until the participant hit the screen with her finger. On each trial, the participant held a key down and maintained central fixation until the target appeared, then released the key and hit the target as quickly and accurately as possible. We recorded participants' eye movements, response latency, movement time and endpoint location. Results: For trials in which the target was displayed for 100ms, saccade latencies were distributed bimodally. For closer targets (2°), observers tended to initiate a hand movement before deploying a saccade. For further targets, saccades were deployed before hand movements. When the target was displayed until the touch, however, saccade latencies were consistently shorter than reach latencies across all target eccentricities. In both stimulus duration conditions, saccade accuracy was more strongly correlated with hand accuracy at 10–12° than for closer targets. Conclusion: Spatial and temporal correlations of eye and hand movements vary as a function of target eccentricity. We suggest this may be due to significant differences in the ability to localise targets at eccentricities greater than 10°. Results suggest eye and hand movements are coordinated with respect to a common map of visual space and are coordinated to improve accuracy and precision of both eye and hand movements.