Biomedical subjects

Agnès Roby-Brami

Publications and source records attributed to Agnès Roby-Brami.

5 recordsLinked to original sources

PubMed2005

Shoulder movements during the initial phase of learning manual wheelchair propulsion in able-bodied subjects.

BACKGROUND: The kinetics and kinematics of the glenohumeral joints, and shoulder muscles activities during the initial phase of learning wheelchair propulsion by individuals with paraplegia have been partially described. But no studies carry out the kinematics of the upper-limb during the learning of non-constrained open field locomotion with a wheelchair. METHODS: Ten subjects with no manual wheelchair experience propelled themselves repetitively straight ahead along an 11m linear path. Upper-limb segment orientations were measured with an electromagnetic system. Angular displacements of joints were determined using a standardized protocol [Wu, G., Van der Helm, F.C.T., Veeger, H.E.J., Makhsous, M., Van Roy, P., Anglin, C., Nagels, J., Karduna, A.R., McQuade, K., Wang, X., Wernerl, F.W., Buchholzm, B., 2005. ISB recommendation on definitions of joint coordinate systems of various joints for the reporting of human joint motion--Part II: shoulder, elbow, wrist and hand. J. Biomech. 38(5), 981-992] and a modeling method [Biryukova, E.V., Roby-Brami, A., Frolov, A.A., Mokhtari, M., 2000. Kinematics of human arm reconstructed from spatial tracking system recordings. J. Biomech. 33, 985-995]. FINDINGS: A full 3-D scapular motion description was obtained that allowed us to measure the mean amplitudes of rotation for the nine degrees of freedom of our model. The change in the propulsion pace and the repetition of trials induced a general increase of amplitudes of joint rotations that can explain the increase of velocity among trials. INTERPRETATION: We did not observe a freezing of any DOF as predicted by Bernstein's theory of motor learning, but the increase in joint movement amplitudes could correspond to his "unfreezing of DOF" stage. This non-respect of Bernstein's theory could originate in the relative simplicity of the task.

Adult↗

PubMed2004

Compensation for distal impairments of grasping in adults with hemiparesis.

Previous studies have shown that patients with arm and hand paresis following stroke recruit an additional degree of freedom (the trunk) to transport the hand during reaching and use alternative strategies for grasping. The few studies of grasping parameters of the impaired hand have been case studies mainly focusing on describing grasping in the presence of particular impairments such as hemi-neglect or optic ataxia and have not focussed on the role of the trunk in prehension. We hypothesized that the trunk movement not only ensures the transport of the hand to the object, but it also assists in orienting the hand for grasping when distal deficits are present. Nineteen patients with chronic hemiparesis and seven healthy subjects participated in the study. Patients had sustained a stroke of non-traumatic origin 6-82 months previously (31+/-22 months) and had mild or moderate to severe arm paresis. Using a whole hand grasp, subjects reached and grasped a cylinder (35 mm) that was placed sagittally (T1) or at a 45 degrees angle to the sagittal midline in the ipsilateral workspace (T2), both at about 90% arm's length (10 trials per target). Eight infrared emitting diodes were placed on bony landmarks of the hand, arm and trunk and kinematic data were recorded by an optical motion analysis system (Optotrak) for 2-5 s at 120 Hz. Hand position and orientation were recorded by a Fastrack Polhemus system. Our results show that during goal-directed prehension tasks, individuals with hemiparesis oriented the hand more frontally for grasping and used more trunk anterior displacement or rotation to transport the hand to the target compared to healthy subjects. Despite these changes, the major characteristics of reaching and grasping such as grip aperture size, temporal coordination between hand transport and aperture formation and the relative timing of grip aperture were largely preserved. For patients with more severe distal impairments, the amount of trunk displacement was also correlated with a more frontal hand orientation for grasping. Furthermore, in healthy subjects and patients without distal impairments, the trunk movement was mostly related to proximal arm movements while in those with distal impairments, trunk movement was related to both proximal and distal arm movements. Data support the hypothesis that the trunk movement is used to assist both arm transport and hand orientation for grasping when distal deficits are present.

Adult↗

PubMed2003

Hand orientation for grasping and arm joint rotation patterns in healthy subjects and hemiparetic stroke patients.

We previously demonstrated that the hand orientation for grasping (azimuth) is strongly coupled to arm movement direction in the horizontal plane. The question is whether this coupling is directly controlled or secondary to a regulation of the arm angular configuration. To this purpose, we quantified hand orientation and arm joint rotations during unconstrained reaching movements in healthy subjects and in patients with hemiparesis due to stroke since they use altered joint rotation patterns for reaching. Seven healthy subjects and eight patients with a right hemiparesis participated (four had a moderate and four had a mild disorder). Four electromagnetic sensors were used to measure hand orientation and to compute the wrist, elbow and shoulder joint angles. Hand azimuth at the time of grasping was correlated to arm movement direction in all the healthy and hemiparetic individuals. In healthy subjects, a regression analysis of the arm joint rotations suggested that the coupling between hand azimuth and movement direction was not due to a correlation with a particular degree of freedom. Patients used different hand orientations for grasping and different joint rotation patterns that varied according to their level of disability and the use of compensatory strategies. The findings observed in both healthy subjects and patients with stroke show that the coupling of hand azimuth for grasping to movement direction was controlled independently of the set of joint rotations used for reaching. This suggests that it is a basic synergy directly controlled by the motor system.

Adult↗

PubMed2002

Coupling between reaching movement direction and hand orientation for grasping.

In a previous work, we demonstrated that orientation of the hand in the horizontal plane (azimuth) at the time of grasping depends on the direction of the reaching movement in the horizontal plane. Here we report three experiments to further investigate the generality of this coupling. Azimuth of the hand for grasping was studied while subjects were reaching for objects placed at various locations on a horizontal board. Hand movements were recorded with an electromagnetic sensor giving information about hand 3D position and orientation. As expected, hand azimuth for grasping was coupled with movement direction in the central part of the workspace (but reached a limit for rightmost reaching directions). The coupling did not depend on the direction of where the object had to be put after grasping. Various initial positions and azimuths of the hand were compared to the most comfortable initial hand posture. The coupling between hand azimuth and movement direction remained whatever the initial hand azimuth. This demonstrates that reaching movement direction is coupled with azimuth at the time of grasping and not with a rotational hand movement. The coupling between hand azimuth and movement direction subsisted when the initial upper trunk orientation was changed. Thus our results cannot be explained by an invariance of the coupling coded in hand-centered or shoulder-centered coordinates. They rather suggest that the movement is produced in a frame of reference associated with the environment.

Adult↗

PubMed2002

Use of the trunk for reaching targets placed within and beyond the reach in adult hemiparesis.

Multijoint movements such as reaching are impaired after brain lesions involving sensorimotor areas and pathways. However, the mechanisms by which such lesions affect motor control are not fully understood. Direct effects of the lesion may be partly compensated by both the system's redundancy and its plasticity. Indeed stroke patients with limited arm movement can reach objects placed within the reach of the arm by using a compensatory strategy involving trunk recruitment. A similar strategy is observed in healthy individuals reaching for objects placed beyond the reach of the arm. Determining the control mechanism(s) governing this compensatory strategy in stroke patients was the goal of this study. Kinematics of reaching movements in hemiparetic and healthy participants to targets placed within and beyond the length of the arm were analysed. Targets were placed sagittally in front of the midline of the body. Two targets (targets 1 and 2) were within reaching distance defined as the length of the stretched arm from axilla to wrist crease. Two others were beyond arm's reach so that one required a forward trunk inclination (target 3) and the other required body raising to a semi-standing position (target 4). Healthy participants used minimal trunk displacement for reaches to targets 1 and 2. For reaches to targets 3 and 4, trunk displacement increased with target distance. Whenever the trunk was involved, there was a stereotyped sequential recruitment of the arm and trunk in that the trunk began moving simultaneously with or before the hand and stopped moving after the end of hand movement. This suggested that the control system predicts that the trunk movement will be needed to extend the reach and includes the trunk, in an anticipatory way, into the reach. In contrast, most hemiparetic participants recruited their trunk for reaches to all four targets, even those placed close to the body. Similar to healthy individuals, the sequence of hand and trunk recruitment was stereotyped, suggesting that temporal planning aspects of the motor program underlying movement coordination were relatively unaffected. In contrast to healthy participants, the contribution of the trunk movement to the endpoint displacement was substantially higher in the hemiparetic group and occurred earlier in the reach. It is suggested that the target distance at which the trunk is integrated into the movement to extend the reach of the arm is attained around the limit of arm extension and that this limit is reduced in hemiparetic individuals.

Adult↗