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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)
1. The control of pointing arm movements in the absence of visual guidance was investigated in unpracticed human subjects. The right arm grasped a lever which restricted the movement of the right index fingertip to a horizontal arc, centered between the axes of eye rotation. A horizontal panel directly above the arm prevented visual feedback of the(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 how sensorimotor adaptation acquired during one experimental session influenced the adaptation in a subsequent session. The subjects' task was to track a visual target using a joystick-controlled cursor, while the relationship between joystick and cursor position was manipulated to introduce a sensorimotor discordance. Each subject(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)
Human subjects pointed, without seeing their arm, at visual targets presented in repeated sequences in a frontal plane. Required movement direction could change within the sequence by 0, 45, 90, 135 or 180°. Hand position was recorded contact-free in three dimensions (3D). From the recordings, the pointing errors towards each target were transformed into a(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)
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° larger or smaller than in the first.(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)
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)