Ocular Gaze is Anchored to the Target of an Ongoing Pointing Movement

Abstract

It is well known that, typically, saccadic eye movements precede goal-directed hand movements to a visual target stimulus. Also pointing in general is more accurate when the pointing target is gazed at. In this study, it is hypothesized that saccades are not only preceding pointing but that gaze also is stabilized during pointing in humans. Subjects, whose eye and pointing movements were recorded, had to make a hand movement and a saccade to a first target. At arm movement peak velocity, when the eyes are usually already fixating the first target, a new target appeared, and subjects had to make a saccade toward it (dynamical trial type). In the statical trial type, a new target was offered when pointing was just completed. In a control experiment, a sequence of two saccades had to be made, with two different interstimulus intervals (ISI), comparable with the ISIs found in the first experiment for dynamic and static trial types. In a third experiment, ocular fixation position and pointing target were dissociated, subjects pointed at not fixated targets. The results showed that latencies of saccades toward the second target were on average 155 ms longer in the dynamic trial types, compared with the static trial types. Saccades evoked during pointing appeared to be delayed with approximately the remaining deceleration time of the pointing movement, resulting in "normal" residual saccadic reaction times (RTs), measured from pointing movement offset to saccade movement onset. In the control experiment, the latency of the second saccade was on average only 29 ms larger when the two targets appeared with a short ISI compared with trials with long ISIs. Therefore the saccadic refractory period cannot be responsible for the substantially bigger delays that were found in the first experiment. The observed saccadic delay during pointing is modulated by the distance between ocular fixation position and pointing target. The largest delays were found when the targets coincided, the smallest delays when they were dissociated. In sum, our results provide evidence for an active saccadic inhibition process, presumably to keep steady ocular fixation at a pointing target and its surroundings. Possible neurophysiological substrates that might underlie the reported phenomena are discussed.

The relative timing between eye and hand in rapid sequential pointing is affected by time pressure, but not by advance knowledge

“…This was based on the finding that eye movements to the second target in a doublestep task occurred prior to the arrival of the finger at the first target, thus necessitating temporary storage of both ocular proprioception and efference commands. Contradictory findings indicating gaze 'anchoring' (Neggers and Bekkering 2000;Neggers and Bekkering 2001) have been explained by the absence of need to make a finger movement to a second target. However, the results of the current study suggest a more complementary account.…”

“…However, rather than being in direct opposition, it is possible that 'gaze anchoring' Bekkering 2000, 2001) and 'buffering' (Wilmut et al 2006) reflect two modes of the visuo-motor system, which operate under different task constraints. A comparison of the experimental methods indicates that the time lag between the two visual stimuli in the study of Neggers and Bekkering (2000) was significantly longer compared (i.e. 585-607 ms) with that in Wilmut et al (2006), i.e., 200 ms.…”

Learning robotic eye–arm–hand coordination from human demonstration: a coupled dynamical systems approach

“…Physiological studies of prehensile motion report that the arm transport and the hand preshape components are coordinated by the motor system in reach-for-grasp maneuvers, even in the presence of perturbations (Castiello et al 1993;Haggard and Wing 1995). Furthermore, there is a strong evidence that control signals also flow from the hand to the eyes, not only in the opposite direction (Fisk and Goodale 1985;Neggers and Bekkering 2000).…”

“…However, some studies report that the control signals also flow from the hand to the eyes (Fisk and Goodale 1985;Neggers and Bekkering 2000), and from the hand to the arm (Timmann et al 1996). Hence, it could be worth addressing the potential benefits of modeling and using bidirectional visuomotor control schemes in robotics.…”

Gaze–mouse coordinated movements and dependency with coordination demands in tracing

“…Eye-hand coordination has been studied in various human behavioural tasks, including object reaching and pointing (Biguer et al 1982;Neggers and Bekkering 2000;Ariff et al 2002;Crawford et al 2004;Masia et al 2009), web browsing (Chen et al 2001;Rodden et al 2008;Guo and Agichtein 2010), goal-directed aiming (Binsted et al 2001;Behan and Wilson 2008), visually guided tracking (Gauthier et al 1988;Vercher and Gauthier 1992;Xia and Barnes 1999;Tramper and Gielen 2011), drawing (Reina and Schwartz 2003;Gowen and Miall 2006;Coen-Cagli et al 2009;Tchalenko and Chris Miall 2009), and trajectory tracing (Gowen and Miall 2006;Tramper and Gielen 2011). Other more complex tasks or applications that combine sequential movements have also attracted growing research interests, such as object manipulation (Johansson et al 2001;Bowman et al 2009) and virtual laparoscopic surgery (Yamaguchi et al 2007).…”