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The bilateral reach-to-grasp movement of Parkinson's disease subjects
Full text linkThe performance of simultaneous movements is said to be disrupted in Parkinson's disease, yet there are some indications that this dysfunction is less evident for bilateral inter-limb actions, as opposed to unilateral simultaneous actions. Focussing specifically upon natural actions, this study uses a three-dimensional kinematic system (ELITE) to assess the movement kinematics of a bilateral non-homologous reach-to-grasp action. The target device consisted of a large cylinder (diameter 8 cm) to which a handle (diameter 0.8 cm) was attached. The task was to reach and grasp the cylinder with one hand (gross grasp) while reaching to grasp the handle with the contralateral hand (precision grasp). Overall the results indicated that Parkinson's disease subjects, like controls showed independent and appropriate kinematic parameterization each limb. For example, and as a reflection of task precision requirements, the time taken to decelerate upon the item to be grasped was longer for the limb grasping the handle than for the limb grasping the cylinder Subtle indications of compensatory mechanisms, in response to left upper limb inadequacies of Parkinson's disease subjects, were suggested by findings of an earlier timing of maximum hand grip aperture for the left than for the right hand, and adjustments to the final transport phase of the left arm under bilateral conditions. It is proposed that left-right hand differences are more evident with basal ganglia dysfunction, bur that these differences are compensated for by CNS mechanisms so that natural non-homologous reach-to-grasp actions are performed in a functional, coordinated and appropriate manner
Reorganization of prehension components following perturbation of object size
No full textThis study provides a kinematic comparison of the response of 12 older persons (ages 60-70) and 12 young persons (ages 20-26) to a perturbation of object size during a reach-to-grasp movement. For 80 out of 100 trials, each participant reached to grasp an illuminated cylinder of either small or large diameter (0.7 and 8.0 cm, respectively). For 20 out of 100 trials, a visual perturbation occurred at movement onset. This perturbation consisted of a switch of illumination from 1 to the other cylinder. For the switch from large to small cylinder, participants changed the distal grasp from whole-hand prehension to precision grip. For the opposite switch, participants changed from precision grip to whole-hand prehension. The older participants successfully adapted to these perturbations but showed a more conservative approach. Generally the approach time as the hand neared the object was prolonged, and the coordination between transport and manipulation components was maintained when comparing perturbed with nonperturbed trials. Young participants showed a more flexible pattern with a decrease or loss of temporal coupling between the components. It is hypothesized that the more rigid movement pattern of older participants to unanticipated motor requirements could be a contributory factor to the higher incidence of accidents for this group
Reach to grasp: changes with age
No full textThis study provides the first known kinematic assessment of the reach-to-grasp movement in elderly subjects. Twelve subjects (aged 60-71) were compared to gender-matched younger subjects (aged 18-25). Subjects reached 35 cm to grasp either a small (0.7 cm) or a large (8 cm) diameter cylinder. Precision grip was naturally adopted for the small cylinder, and whole hand prehension for the large cylinder. The displacements of active infrared markers (wrist and hand) were recorded with an Optotrak system. Movement initiation time, movement duration, and kinematic parameters of the reach-and-grasp components were computed. Older subjects showed slower, longer movements with a prolonged approach phase. However, the patterning and coordination of this movement, with respect to the utilization of a precision grip or whole hand prehension, were similar for both groups. Subtle changes with age thus appear to reflect a strategy that develops to compensate for deterioration in other systems such as visual or proprioceptive
Parkinson's disease: reorganization of the reach to grasp movement in response to perturbation of the distal motor patterning
No full textThis study assessed the kinematic changes to the reach to grasp movement in,response to a perturbation of object size in 15 Parkinson's disease (PD) and 15 control subjects. For non-perturbed trials subjects reached 35 cm to grasp and lift either an illuminated small (0.7 cm) or large (8 cm) diameter cylinder. For perturbed trials (20%), illumination shifted unexpectedly from the small to the large or from the large to the small cylinder at the onset of the reach. For Condition One trials subjects were given no instructions as to which grasp to use. With perturbation, they thus naturally changed grasp from precision grip to whole hand prehension or vice versa. The results for the PD subjects indicated a slowness at the transition from one to another grasp. This contrasted to the smooth transitions when perturbation required only a change of grasp aperture (precision grip-Condition Two. whole hand prehension-Condition Three). PD subjects thus showed dysfunction in the suppression/activation of different grasp programs rather than deficits in the on-line modification of an operating program
How perceived object dimension influences prehension
No full textA kinematic study assessed the effects of the perceived dimensions of an object upon the patterning of a prehension movement involving that object. If an apple was perceived as two-dimensional, subjects utilized a large precision grip between the index finger and thumb. If the apple was perceived as three-dimensional, whole hand prehension involving all the digits was utilized. A visual perturbation from perceived two-dimensional to three-dimensional at movement onset resulted in a transition from the 2D precision grip pattern to the 3D whole hand prehension. These results suggest that visual mechanisms for interpreting the dimensions of an object directly influence motor selection pathways, and do not necessarily access a three-dimensional central nervous system representation of the object
Reach to grasp: the natural response to perturbation of object size
No full textThis study assessed the reach to grasp movement and its adaptive response to a perturbation of object size. In blocked trials, subjects (n = 12) were instructed to reach 35 cm to grasp and lift a small- (0.7 cm) or large-diameter (8 cm) cylinder. Under an unconstrained condition (condition 1), no instructions as to the type of grasp to adopt were given. Subjects thus naturally used a precision grip (PG) for the small cylinder and whole hand prehension (WHP) for the large cylinder. Under condition 2, subjects were instructed to utilize a PG for grasps of both the large and small cylinders. For condition 3, the instruction was to use WHP irrespective of object size. Kinematic organization was determined with analysis of the recordings of active markers placed on the wrist, thumb, and three fingers. For condition 1 the results showed a temporal arrangement of both components (transport and manipulation) which differed from that of conditions 2 and 3. In perturbed trials, illumination shifted from the small to large cylinder or vice versa. With condition 1, subjects automatically switched from one grasp to another with no or little increase of movement duration. This was generally achieved by an earlier temporal setting of peak wrist deceleration. For conditions 2 and 3, where a change of aperture was required, movement duration was prolonged without adaptation of earlier transport component parameters. It is concluded that the adaptive responses to a change of distal patterning also affect the organization of the proximal component. Assessment of grasps constrained by instructions may lead to interpretations of central control of the reach to grasp movement which differ from those obtained by assessing more natural prehensile patterns
Three-dimensional covert attentional functions in Parkinson's disease subjects
No full textThis study assessed the ability of mildly affected Parkinson's disease (PD) subjects (n=16) to perform attentional cognitive tasks within a three-dimensional object. A hollow cube was displayed on a computer screen and the subject was required to respond as quickly as possible to the highlighting of one of the cube angles by pressing the spacebar of the keyboard. Prior to the appearance of this imperative stimulus, the same (''valid'' trials) or an alternative (''invalid'' trials) angle was highlighted. For the invalid trials this meant that the subject oriented attention to the cued angle but, on imperative stimulus appearance, was unexpectedly required to redirect attention to another angle, which could be on a different cube face to that which had been cued. For one experimental session the cube was stationary, that is, object-centred and viewer-centred coordinates of a cube angle corresponded. For another session, the cube rotated such that the viewer-centred coordinates of an angle changed between appearance of the cue and appearance of the stimulus, but the angle's object-centred coordinates remained constant. The finding of lower reaction times for the valid than for the invalid trials, even when the cube was rotating, indicated that PD subjects could operate attention using an object-centred coordinate system. However, PD subjects showed exaggerated reaction times when the stimulus appeared in a cube face that was opposite to, rather than the same as, that of the invalidly cued angle. It is suggested that this reflects a dysfunction in the grouping of the structural components of the whole object at an attentional level
The bilateral reach to grasp movement
No full textThis study investigated the kinematic organization of bilateral reach to grasp movements. In Experiment 1 non-homologous bilateral movements were performed. One limb reached to grasp an object using whole hand prehension; the contralateral limb simultaneously reached to grasp an object using precision grip. Corresponding unilateral movements were assessed. Movement duration for each limb in the bilateral condition was similar. However, with earlier temporal settings for peak wrist acceleration and velocity, the limb performing precision grip showed a longer approach (deceleration) phase to the object. Unilateral precision grip movements showed a longer movement duration and deceleration phase than unilateral whole hand prehension movements. In Experiment 2 homologous bilateral movements were assessed. Both limbs performed either a reach and whole hand prehension or a reach and precision grip. Again the precision grip movements showed longer movement and deceleration times. Experiment 3 consisted of bilateral non-homologous pointing movements and a pointing movement with one limb while reaching to grasp with the contralateral limb. It was found that the earlier temporal settings of peak acceleration and velocity with the precision grip limb of the non-homologous bilateral task (Expt. 1) were largely due to the performance of distal grasping actions. It is concluded that a kinematic parameterization which is independent to each limb is evident for bilateral tasks which require functionally independent actions
The drinking action of Parkinson's disease subjects
No full textUsing the ELITE system, a kinematic analysis was performed of the upper limb drinking action of nine Parkinson's disease patients and nine control subjects. The aim was to use a natural task to investigate the reported Parkinson's disease dysfunction in the performance of simultaneous and sequential movements. Subjects were required to reach 28 cm, grasp a half-filled glass and then rake a sip of water. Dysfunction for simultaneous movements was supported by the finding that, in both absolute and relative terms, Parkinson's disease subjects often began to open the hand later than control subjects. Dysfunction for sequential movements was supported by the finding that Parkinson's disease subjects often showed a pause between the first ('reach-grasp') and second ('take-to-lips') parts of the drinking action. Despite these delays and pauses, the proportional organization of the action was similar for both groups. This suggested that Parkinson's disease subjects were able to compensate for the problem in activating the different components of the drinking action. The results are discussed in relation to the influence of the abnormal basal ganglia input to cortical motor regions
A kinematic study of the reach to grasp movement in a subject with hemiParkinson's disease
No full textThe kinematic organization of a reach to grasp movement in a left hemiParkinson subject is compared to that of a control subject. Subjects used the right and left limbs to reach 15, 27 or 40 cm for the grasp of cylinders of 0.7 or 8 cm diameter. In general, the kinematics of the affected limb of the hemiParkinson subject differed from that of the unaffected limb. However, for both arms the hemiParkinson subject showed a delay in the onset of the manipulation component. The subtle dysfunction in the activation of near-simultaneous or sequential movements is thus bilateral, despite unilateral clinical symptomatology
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