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Exp Brain Res (2009) 195:445454 DOI 10.1007/s00221-009-1812-7
RESEARCH ARTICLE
The hands automatic pilot can update visual information while the eye is in motion
Brendan D. Cameron James T. Enns Ian M. Franks Romeo Chua
Received: 29 July 2008 / Accepted: 8 April 2009 / Published online: 29 April 2009 Springer-Verlag 2009
Abstract When participants reach for a target, their hand can adjust to a change in target position that occurs while their eyes are in motion (the hands automatic pilot) even though they are not aware of the targets displacement (saccadic suppression of perceptual experience). However, previous studies of this eVect have displayed the target without interruption, such that the new target position remains visible during the Wxation that follows the saccade. Here we test whether a change in target position that begins and ends during the saccade can be used to update aiming movements. We also ask whether such information can be acquired from two targets at a time. The results showed that participants responded to single and double target jumps even when these targets were extinguished prior to saccade termination. The results imply that the hands automatic pilot is updated with new visual information even when the eye is in motion.
Keywords Saccade Manual aiming Online control Sequential aiming
Introduction
When we reach for an object, the object is usually the target of our visual Wxation before our hand contacts the object. Studies of rapid aiming suggest that a rough command to
move the limb is generated ahead of an orienting saccade. The action command is then reWned online, once the eyes acquire the target (Desmurget and Grafton 2000; Gribble et al. 2002). Double-step studies (so called because the target is displaced twice: once ahead of the orienting saccade and once during the saccade) have demonstrated that the motor command to the hand is modiWed in response to the displaced target, even though the participant is unaware of the jump (e.g., Bridgeman et al. 1979; Goodale et al. 1986; Prablanc and Martin 1992). These rapid corrections to target jumps are thought to be under the control of an automatic pilot (Pisella et al. 2000), which guides the hand independently of conscious intention or awareness.1
The lack of awareness experienced during the eye movement...