Biomedical subjects

Pierre-Michel Bernier

Publications and source records attributed to Pierre-Michel Bernier.

5 recordsLinked to original sources

PubMed2006

Updating of an internal model without proprioception: a deafferentation study.

This study sought to determine whether intact proprioception is required to adapt to a novel kinematic environment. We compared adaptation with a rotated visual feedback between a deafferented patient and healthy participants. They performed reaching movements towards visible targets while vision of the cursor was rotated by 30 degrees with respect to hand position. The patient adapted at the same rate and to the same extent as the controls when exposed to the rotated visual feedback. She also presented large aftereffects following removal of the perturbation. This suggests that proprioception is not an absolute requirement to update a kinematic internal model. Adaptation was likely mediated by a comparison between the sensory consequences of a movement as predicted by a forward model and the visual feedback from that movement.

Adaptation, Physiological↗

PubMed2006

Sensorimotor adaptation in response to proprioceptive bias.

Studies investigating visuo-motor adaptation typically introduce sensory conflicts by manipulating visual information (prisms, cursor gains). The purpose of the present study was to determine whether similar adaptation would be observed when a conflict is created through distortion of the proprioceptive sense, rather than through visual distortion. We used a coordinated movement task that required participants to release thumb and index finger at a specific elbow angle during passive elbow extension. Participants could not see their arm, but were shown a cursor representing the forearm on a video screen. In the proprioceptive group, a sensory conflict was introduced by vibrating the biceps brachii muscle, introducing a discrepancy of approximately 7.5 degrees between the proprioceptively perceived and visually perceived elbow angle. In the visual group, a conflict of similar magnitude was obtained by introducing a gain of 7.5 degrees to the cursor with respect to forearm position. Adaptation was assessed by the presence of plastic changes in release elbow angles following a period of exposure to the sensory conflict (i.e., aftereffects). Both groups showed high accuracy during exposure despite the sensory conflicts. More importantly, the visual group presented large and persistent aftereffects, while the proprioceptive group presented none. We suggest that the proprioceptive group's lack of adaptation was due to the artificial muscle spindle activity resulting from vibration, which prevented visual and proprioceptive signals to be merged into a common frame of reference.

Adaptation, Physiological↗

PubMed2006

Inferring online and offline processing of visual feedback in target-directed movements from kinematic data.

Vision plays an important role in the planning and execution of target-directed aiming movements. In this review, we highlight the limitations that exist in detecting visual regulation of limb trajectories from traditional kinematic analyses such as the identification of discontinuities in velocity and acceleration. Alternative kinematic analyses that involve examining variability in limb trajectories to infer visual control processes are evaluated. The basic assumption underlying these methods is that noise exists in the neuromotor system that subsequently leads to variability in motor output. This leads to systematic relations in limb trajectory variability at different stages of the movement that are altered when trajectories are modified during movement execution. Hence, by examining the variability in limb trajectories and correlations of kinematic variables throughout movement for vision and no vision conditions, the contribution of visual feedback in the planning and control of movement can be determined.

Animals↗

PubMed2006

Determinants of offline processing of visual information for the control of reaching movements.

The authors investigated the use of visual feedback as a form of knowledge of results (KR) for the control of rapid (200-250 ms) reaching movements in 40 participants. They compared endpoint accuracy and intraindividual variability of a full-vision group (FV) with those of no-vision groups provided with KR regarding (a) the endpoint in numerical form, (b) the endpoint in visual form, or (c) the endpoint and the trajectory in visual form (DEL). The FV group was more accurate and less variable than were the no-vision groups, and the analysis of limb trajectory variability indicated that their superior performance resulted primarily from better movement planning rather than from online visual processes. The FV group outperformed the DEL group even though both groups were obtaining the same amount of spatial visual information from every movement. That finding suggests that the effectiveness with which visual feedback is processed offline is not a simple function of the amount of visual information available, but depends on how that information is presented.

Adult↗

PubMed2005

Is proprioception calibrated during visually guided movements?

In the present study, a visuomotor adaptation paradigm was used to determine whether proprioception is calibrated during visually guided movements. A full vision group (FV) was given vision of a cursor representing hand position and was asked to aim towards visible targets. A no vision group (NV) performed the same task without vision of the cursor and was given knowledge of results (KR) after movement completion. A directional bias was introduced between the location of the cursor and the location of the hand in an adaptation phase, which resulted in a deviation to the right of the intended target. Of interest was whether participants would still show rightward deviations in a post-test series of trials in which vision was removed (aftereffects). The NV group presented strong aftereffects. However, the FV group only showed modest aftereffects early in the post-test, which rapidly decayed over the course of the post-test. Further analyses showed that the presence of those early aftereffects was due to an offline influence of vision on movement planning.

Adult↗