Target selection in eye-hand coordination: Do we reach to where we look or do we look to where we reach?
A. Horstmann & K.-P. Hoffmann
Exp.Brain Res., on-line Juli 2005
- During a goal-directed movement of the hand to a visual target the controlling nervous system depends on information
provided by the visual system. This suggests that a coupling between these two systems is rucial. In a choice condition
with two or more equivalent objects present at the same time the question arises whether we (a) reach for the object
we have selected to look at or (b) look to the object we have selected to grasp. Therefore, we examined the preference
of human subjects selecting the left or the right target and its correlation to the action to be performed (eye-,
arm- or coordinated eye-arm movement) as well as the horizontal position of the target. Two targets were presented
at the same distance to the left and right of a fixation point and the stimulus onset asynchrony (SOA) was adjusted
until both targets were selected equally often. This balanced SOA was then taken as a quantitative measure of selection
preference. We compared these preferences at three horizontal positions for the different movement types (eye,
arm, both). The preferences of the 'arm' and 'coordinated eye-arm' movement types were correlated more strongly
than the preferences of the other movement types. Thus, we look to where we have already selected to grasp. These
findings provide evidence that in a coordinated movement of eyes and arm the control of gaze is a means to an end,
namely a tool to conduct the arm movement properly.
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