Modelling gait processes as a combination of sensory-motor and cognitive controls in an attempt to describe accidents on the level in occupational situations.

In occupational situations, accidents referred to as accidents on the level (AoLs) occur most of the time when locomotion control fails. This control is determined by the interactions between the operator and the environment, the task and the used tools. Hence, AoLs prevention requires developing ways to optimise these interactions.

Influence of feedback modality on sensorimotor adaptation: contribution of visual, kinesthetic, and verbal cues.

In 4 studies, the authors tested the contributions of visual, kinesthetic, and verbal knowledge of results to the adaptive control of reaching movements toward visual targets. The same apparatus was used in all experiments, but the procedures differed in the sensory modality of the feedback that participants (N s = 5, 5, 6, and 6, respectively, in Experiments 1, 2, 3, and 4) received about their performances. Using biased visual, proprioceptive, or verbal feedback, the authors introduced a 5 degrees shift in the visuomanual relationship.

Evidence for distinct, differentially adaptable sensorimotor transformations for reaches to visual and proprioceptive targets.

Recent evidence suggests that planning a reaching movement entails similar stages and common networks irrespective of whether the target location is defined through visual or proprioceptive cues. Here we test whether the transformations that convert the sensory information regarding target location into the required motor output are common for both types of reaches. To do so, we adaptively modified these sensorimotor transformations through exposure to displacing prisms and hypothesized that if they are common to both types of reaches, the aftereffects observed for reaches to visual targets would generalize to reaches to a proprioceptive target.

Adaptive control: a review of the ability to acquire and maintain high sensorimotor performance.

When the relationship which relates us to the environment through vision, often named visual mapping, is durably modified, our behaviour is altered at sensory, motor and cognitive levels. The brain has the ability through the so-called adaptive control to progressively decrease the motor errors despite visual image alteration. Adaptive control in both the visuo-manual and the vestibulo-ocular systems is reviewed.

Internally driven control of reaching movements: a study on a proprioceptively deafferented subject.

We investigated the possibility of controlling reaching movements on the sole basis of central mechanisms, i.e., without peripheral feedback on hand and target positions.

On the nature of the vestibular control of arm-reaching movements during whole-body rotations.

Recent studies report efficient vestibular control of goal-directed arm movements during body motion. This contribution tested whether this control relies (a) on an updating process in which vestibular signals are used to update the perceived egocentric position of surrounding objects when body orientation changes, or (b) on a sensorimotor process, i.e.

Head positioning control in a gravito-inertial field and in normal gravity.

The way in which the head is controlled in roll was investigated by dissociating the body axis and the gravito-inertial force orientation. Seated subjects (N = 8) were requested to align their head with their trunk, 30 degrees to the left, 30 degrees to the right or with the gravito-inertial vector, before, during (Per Rotation), after off-center rotation and on a tilted chair without rotation (Tilted). The gravito-inertial vector angle during rotation and the chair tilt angle were identical (17 degrees ).

Shifts in the retinal image of a visual scene during saccades contribute to the perception of reached gaze direction in humans.

We tested whether the perception of gaze direction is affected by the shifts in the retinal image of the visual scene during eye movements. To do so, we displaced the visual scene during saccadic eye movements and measured whether these unconsciously-detected shifts altered subjects' perception of the reached gaze direction. While facing a visual environment composed of light-emitting diodes, subjects first performed a rightward saccade of a great amplitude before producing a leftward saccade towards a target that appeared in the environment.

Online control of the direction of rapid reaching movements.

Online visual control of the direction of rapid reaching movements was assessed by evaluating how human subjects reacted to shifts in seen hand position near movement onsets. Participants ( N=10) produced saccadic eye and rapid arm movements (mean duration = 328 ms) towards a peripheral visual target in complete darkness. During the saccade, visual feedback of hand position could be shifted by 1, 2, 3 or 4 cm perpendicularly to the main movement direction.

Target and hand position information in the online control of goal-directed arm movements.

The present study compared the contribution of visual information of hand and target position to the online control of goal-directed arm movements. Their respective contributions were assessed by examining how human subjects reacted to a change of the position of either their seen hand or the visual target near the onset of the reaching movement. Subjects, seated head-fixed in a dark room, were instructed to look at and reach with a pointer towards visual targets located in the fronto-parallel plane at different distances to the right of the starting position.

[Targets of the memorized position and visual contexts].

The goal of this study was to determine whether a sensorimotor or cognitive encoding is used to encode a target position and save it into iconic memory. The methodology consisted of disrupting a manual aiming movement to a memorized visual target by displacing the visual field containing the target. The nature of the encoding was inferred from the nature and the size of the errors relative to a control.

On-line versus off-line vestibular-evoked control of goal-directed arm movements.

The present study tested whether vestibular input can be processed on-line to control goal-directed arm movements towards memorized visual targets when the whole body is passively rotated during movement execution. Subjects succeeded in compensating for current body rotation by regulating ongoing arm movements. This performance was compared to the accuracy with which subjects reached for the target when the rotation occurred before the movement.

Visual signals contribute to the coding of gaze direction.

Accurate information about gaze direction is required to direct the hand towards visual objects in the environment. In the present experiments, we tested whether retinal inputs affect the accuracy with which healthy subjects indicate their gaze direction with the unseen index finger after voluntary saccadic eye movements. In experiment 1, subjects produced a series of back and forth saccades (about eight) of self-selected magnitudes before positioning the eyes in a self-chosen direction to the right.