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J Neurophysiol (July 16, 2008). doi:10.1152/jn.90518.2008
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Submitted on April 30, 2008
Revised on June 22, 2008
Accepted on July 13, 2008

Gaze Behavior When Reaching to Remembered Targets

J Randall Flanagan1, Yasuo Terao, and Roland S. Johansson2*

1 Queen's University
2 University of Umea

* To whom correspondence should be addressed. E-mail: roland.s.johansson{at}physiol.umu.se.

People naturally direct their gaze to visible hand movement goals. Doing so improves reach accuracy through use of signals related to gaze position and visual feedback of the hand. Here, we investigated where people naturally look when acting on remembered target locations. Four targets were presented on a screen, in peripheral vision, while participants fixed a central cross (encoding phase). Four seconds later participants used a pen to mark the remembered locations while free to look wherever they wished (recall phase). Visual references, including the screen and the cross, were present throughout. During recall, participants neither looked at the marked locations nor prevented eye movements. Instead, gaze behavior was erratic and comprised gaze shifts loosely coupled in time and space with hand movements. To examine if eye and hand movements during encoding affected gaze behavior during recall, in additional encoding conditions participants marked the visible targets with either free gaze or with central cross fixation, or just looked at the targets. All encoding conditions yielded similar erratic gaze behavior during recall. Furthermore, encoding mode did not influence recall performance, suggesting that participants, during recall, did not exploit sensorimotor memories related to hand and gaze movements during encoding. Finally, we recorded a similar lose coupling between hand and eye movements during an object manipulation task performed in darkness after participants had viewed the task environment. We conclude that acting on remembered versus visible targets can engage fundamentally different control strategies, with gaze largely de-coupled from movement goals during memory-guided actions.







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Copyright © 2008 by the The American Physiological Society.