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In human subjects, we investigated the accuracy of goal-directed arm movements performed without sight of the arm; errors of target localization and of motor control thus remained uncorrected by visual feedback, and became manifest as pointing errors. Target position was provided either as retinal eccentricity or as eye position. By comparing the results to(More)
We investigated whether deficits of adaptive improvement in seniors are related to an age-dependent decay of the brain's executive functions. Younger and older subjects completed a battery of cognitive tests, and preformed aimed arm movements before and during exposure to rotated visual feedback. In accordance with previous work, we found that adaptive(More)
Previous studies have found that sensorimotor adaptation to visual distortions is degraded in seniors compared with younger subjects, whereas after-effects on removal of the distortion are age-independent. The latter finding was interpreted as evidence that adaptive recalibration is not affected by old age, and that the observed degradation is therefore due(More)
We investigated visual localization by asking humans to point at visual objects without vision of their hand. The objects were luminous discs, presented stereoscopically at different distances, eccentricities and meridians with respect to the subjects' straight-ahead. Final pointing position was recorded by an electromagnetic search-coil technique. We found(More)
The present study investigates if sensorimotor adaptation to large visual rotations is achieved by a continuous angular change of the internal representation of space. Human subjects performed manual tracking movements under rotated visual feedback in two sessions; the magnitude of rotation in the second session was 45 degrees larger or smaller than in the(More)
Human subjects pointed, without sight of their arm, at visual targets presented on a mirror-viewed monitor screen. During the adaptation period of each experiment, the position of the pointing fingertip was continuously recorded and displayed on the screen along with the targets. This visual feedback was not always veridical; rather, it was manipulated to(More)
The present study investigated the mechanisms involved in the preparation of pointing movements in humans. We provided visual precues on the location of the upcoming target, and registered the effect of these precues on the reaction time (RT = interval between target appearance and movement onset). Generally, precues were found to reduce RT, suggesting that(More)
Previous research has shown that subjects can adapt with either arm to an opposite visual distortion, and the two adaptive states can then be used in sequence to control the respective arm. To extend this finding, we exposed the left and right arms of our subjects to opposite-directed rotations of the visual field alternately for 20 s each, and determined(More)
This review summarizes our present knowledge about elderly people's problems with walking. We highlight the plastic changes in the brain that allow a partial compensation of these age-related deficits and discuss the associated costs and limitations. Experimental evidence for the crucial role of executive functions and working memory is presented, leading(More)
We investigated the mechanisms of sensorimotor adaptation by sequentially exposing human subjects to different visual distortions. Subjects performed a manual tracking task, while the relationship between their actual finger movement and its visual feedback was manipulated either by a position-to-position (PP), or by a position-to-velocity (PV)(More)