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Biomedical subjects

A M Gentile

Publications and source records attributed to A M Gentile.

15 recordsLinked to original sources
PubMed2004

Rehabilitation of reaching after stroke: task-related training versus progressive resistive exercise.

OBJECTIVE: To evaluate the effectiveness of 2 rehabilitative approaches for improving paretic limb reaching by chronic stroke subjects. DESIGN: Pre- and posttest reaching to targets ipsilateral, midline, and contralateral to the impaired side. SETTING: Training in subjects' homes; testing in a laboratory setting. PARTICIPANTS: Twelve poststroke volunteers were matched using the Motor Assessment Scale (MAS) and then were randomly assigned to 1 of 2 training conditions. Subjects were subsequently categorized as at a high or low functional level, using the reaching pretest movement time scores. INTERVENTIONS: Training (trunk unrestrained) using the paretic limb was 4 weeks (12 sessions). Task-related training (TRT) involved reaching to objects placed across the workspace. Progressive resistive exercise (PRE) involved whole-arm pulling against resistive therapeutic tubing in planes and distances similar to that in TRT. Main outcome measures Kinematic analysis of arm trajectory and trunk motion using the Peak Performance System, as well as scores on the MAS and the Rivermead Motor Assessment (RMA). RESULTS: For low-level groups, TRT resulted in increased substitutive trunk use at the target ipsilateral to the moving arm, and for midline and contralateral targets after PRE. Only low-level, TRT subjects straightened hand paths, which suggested better coordination of elbow-shoulder motion, and improved on the RMA. High-level subjects decreased trunk use at ipsilateral target after PRE, which was not observed after TRT. No significant differences between training conditions were found for other kinematic variables. CONCLUSIONS: Training benefits appear to depend on initial level of functioning. Although compensatory trunk use was evident, low-level subjects seemed to benefit most from TRT. High-level subjects, whose kinematics showed fairly normal movement organization, demonstrated less compensatory movement after PRE.

Aged↗
PubMed2004

Form and variability during sit-to-stand transitions: children versus adults.

In performing the sit-to-stand transition, young children (6- to 7-year-olds) were expected to display a movement form similar to that of adults. However, movement consistency was predicted to be poorer in children than in adults because they lack refinement of motor control processes. Kinematic analysis of 10 repetitions of the sit-to-stand movement was carried out for 6 typically developing children and 6 adults. Supporting the authors' prediction of comparable form, no differences were evident between age groups for sequence of joint onsets, proportional duration of segmental motion, or in angle-angle plots of displacement at 2 segments. In contrast, within-participant variability was found to be higher for children: Coefficients of variation for most kinematic measures were twice those seen for adults. The authors interpret the children's lack of movement consistency as a reflection of inadequate stabilization of an internal model of intersegmental dynamics. Whereas adults have attained a skill level associated with refinement of that model, children have not. Children have an additional control problem because changes in body morphology throughout childhood require ongoing updating of the internal model that controls intrinsic dynamics.

Adult↗
PubMed2003

Prehension in young children with Down syndrome.

Prehension was examined in 3-year old children with Down syndrome (DS, n = 3) and in typically-developing children matched in chronological age (3-year olds; n = 3) or mental age and motor experience (2-year olds; n = 3). The task required reaching to grasp dowels. Video-based movement analysis yielded temporal and kinematic measures. Children with DS were hypothesized to have deficits in feedback-dependent components of prehension (anticipatory grip-closure and deceleration of reach), whereas feedforward components (reach's acceleration phase; grasp's preshaping) were assumed to be unimpaired [Latash, 1993, Control of human movement, pp. 283-292; Latash, 1994, What is clumsiness? In: Motor Control and Down Syndrome II Proceedings of the second international conference, pp. 68-71]. The findings supported these hypotheses. In comparison to control groups, children with DS had significantly: (a) less time in deceleration of reaching, (b) fewer anticipatory grip-closures, and (c) longer movement times for dowel-lift. Young children with DS appeared to use dowel-contact to decelerate the limb and initiate grip-closure. In contrast, reach-acceleration time and grasp-preshaping did not differ across groups. These findings suggest that children with DS display qualitative differences in motor capabilities rather than simply a delayed rate of typical developmental progression.

Child, Preschool↗
PubMed1998

The reaching movements of patients with Parkinson's disease under self-determined maximal speed and visually cued conditions.

Two-dimensional kinematic analysis was performed of the reaching movements that six subjects with Parkinson's disease and six healthy subjects produced under self-determined maximal speed and visually cued conditions. Subjects were required to reach as fast as possible to grasp a ball (i) that was fixed stationary in the centre of a designated contact zone on an inclined ramp (self-determined maximal speed condition), or (ii) that rolled rapidly from left to right down the incline and into the contact zone (visually cued condition). Parkinson's disease subjects displayed bradykinesia when performing maximal speed reaches to the stationary ball, but not when they reached for the moving ball. In response to the external driving stimulus of the moving ball, Parkinson's disease subjects showed the ability to exceed their self-determined maximal speed of reaching and still maintain a movement accuracy that was comparable to that of healthy subjects. Thus, the bradykinesia of Parkinson's disease subjects did not seem to be the result of a basic deficit in their force production capacity or to be a compensatory mechanism for poor movement accuracy. Instead, bradykinesia appeared to result from the inability of Parkinson's disease subjects to maximize their movement speed when required to internally drive their motor output. The occasional failure of Parkinson's disease subjects to successfully grasp the moving ball suggested errors of coincident anticipation and impairments in grasp performance rather than limitations in the speed or accuracy of their reaches. These results are discussed in relation to the notion that the motor circuits of the basal ganglia play an important role in the modulation of internally regulated movements.

Aged↗
PubMed1995

The coordination between trunk and arm motion during pointing movements.

The coordination between the trunk and arm of six subjects was examined during unrestrained pointing movements to five target locations. Two targets were within arm's length, three were beyond. The trunk participated in reaching primarily when the target could not be attained by arm and scapular motion. When the trunk did contribute to hand transport, its motion started simultaneously with arm movement and continued until target contact. Redundancy in the degrees of freedom used to execute the movement had no effect on the configuration of joints and segments used to attain a specified target; no difference in variability was noted regardless of whether redundancy existed. However, different configurations were used to achieve the same wrist coordinates along a common endpoint path, depending on the final position of the hand. The addition of trunk flexion, rotation and scapular motion did not alter the coupling between the elbow and shoulder joints and had no effect on the path of the hand or the smoothness of its velocity profile. Thus, trunk motion was integrated smoothly into the transport phase of the hand. As the trunk's contribution to hand transport increased, it played a progressively greater role in positioning the hand close to the target during the terminal stage of the reach. Of the movement components measured, trunk flexion was the last component to complete its motion when target reaches were made beyond arm's length. Hence, the trunk not only acts as a postural stabilizer during reaching, but becomes an integral component in positioning the hand close to the target.

Adult↗
PubMed1989

A kinematic comparison of single and multijoint pointing movements.

Rapid pointing movements (no accuracy or reaction time requirements) were performed under three conditions which limited motion to the shoulder, elbow or a combination of these two joints. Velocity profiles of the hand's trajectory differed during single and multijoint movements. For the same magnitude of displacement, the hand always had a higher peak velocity, shorter rise time (time to peak velocity) and shorter movement time during single joint movements. However, when the profiles were normalized with respect to amplitude and movement time, no significant differences were observed between these three movement conditions. The velocity profiles of the elbow and/or shoulder were also compared under single and multijoint movement conditions. Analysis of these profiles revealed that the relationships between peak velocity and displacement and between movement time and displacement remained the same at the shoulder joint during single and multijoint movements. In contrast, the elbow joint velocity profiles were significantly affected by movement conditions. These relationships (peak velocity/displacement and movement time/displacement) changed during multijoint movements and became the same as those observed at the shoulder joint. The shape of the hand velocity profile and its invariance across movement conditions can best be explained by dynamic optimization theory and supports the notion that movement of the hand is of primary importance during rapid pointing. However, the consistency of the shoulder velocity profile and the highly significant relationships between the movement of the elbow and shoulder joints indicates that a subordinate joint planning strategy is also used. The purpose of this strategy is to functionally decrease the available degrees of freedom and to simplify coordination between the moving joints. Thus, the organization of arm movements is hierarchically structured with important, but different contributions being made on both the hand planning and joint planning levels.

Adult↗
PubMed1987

Enrichment versus exercise effects on motor impairments following cortical removals in rats.

Groups of rats were exposed to an enriched environment, given access to an activity wheel, or individually housed in wire mesh cages, impoverished. Rats were exposed in groups of four to the enriched environment or placed individually in the activity wheel for 2 h per day for 25 days preoperatively. Within each exposure group, rats sustained bilateral removals of sensorimotor cortex, or were sham-operated controls. Animals were trained preoperatively to locomote across a narrow elevated runway. Postoperatively, locomotor testing was initiated 17 days after surgery throughout which time all animals were maintained under impoverished conditions. Locomotor deficits following cortical damage were a function of preoperative exposure: enriched rats were least impaired; impoverished rats were most impaired. Rats allowed running wheel activity initially showed the same marked deficits as impoverished animals but recovered more rapidly. The opportunity for physical exercise afforded wheel animals preoperatively may have enhanced motor capabilities that aided recovery. However, physical activity alone did not yield the same protective effects from initial impairment as enrichment. Greater elaboration of neural structures associated with perceptual-motor enrichment probably accounted for the initial sparing of the enriched group.

Animals↗
PubMed1986

Joint control strategies and hand trajectories in multijoint pointing movements.

The role of timing in the control of multijoint pointing movements was evaluated. Eight subjects performed rapid pointing movements to a variety of target locations. The subject's right arm was strapped to a 2 degrees of freedom manupilandum that permitted shoulder and elbow motion in the horizontal plane. Initial and final position of the hand and magnitude of displacement was varied to determine effects on timing characteristics. Kinematics and kinetics of the shoulder, elbow, and hand were analyzed. The hand paths and velocity profiles observed were consistent with prior reports. Multiple regression analysis of kinematic variables disclosed that timing of joint movement onset was independent of initial and final positions of the hand, but was linearly related to joint displacement: the joint that moved farther started moving first. Using computer simulations to create joint movement onset, times that were different from the observed ones always resulted in hand paths with increased curvatures and loss of the smooth velocity profiles. Secondly, a very stable, linear relationship was observed between peak velocity and displacement at both the elbow and shoulder joints. This relationship was not affected by variations in movement space. We suggest that space-time transformation based on difference in joint displacement is used to regulated timing of joint movement onset. The simulations indicate that this transformation is set to produce smooth velocity profiles. The relationships between timing of movement onset and displacement and between peak velocity and displacement complement each other: by maintaining a linear relationship between velocity and displacement, a linear space time transformation can be used to control timing. Furthermore, these relationships are probably used to simplify coordination between the moving joints.

Journal Article↗
PubMed1985

Environmental influences on locomotor recovery following cortical lesions in rats.

Groups of rats were exposed to an enriched environment 2 hr per day for 30 days during the immediate pre- and/or postoperative period, or not at all. Animals in four of these groups sustained lesions in the bilateral sensorimotor cortex. One sham-operated control group was enriched pre- and postoperatively; a second control group was not. Animals were trained preoperatively to locomote across a narrow elevated runway. Testing on the locomotor task began 31 days after surgery and continued until preoperative performance levels were achieved. Preoperative enrichment had the most potent influence on initial deficit and recovery of locomotion. Animals that were enriched preoperatively failed to demonstrate any deficit postoperatively, and the topology of their hindlimb movement appeared to be normal. In preoperatively impoverished animals, postoperative enrichment reduced the degree of initial deficit and speeded recovery of locomotion when compared with animals not enriched at all. However, preoperatively impoverished rats demonstrated an aberrant topology of hindlimb movement even after they were "behaviorally recovered".

Animals↗
PubMed1972

Movement organization and delayed alternation behavior of monkeys following selective ablation of frontal cortex.

The delayed alternation problem was tested in monkeys either according to the routine procedure (SS test), or when additional cues were added which were operating in the moment of executing the response. These additional cues involved different sensations in effort of the perfomed movement – sliding heavy object vs. sliding light object (sS test), as well as different sensations in pattern of movement and joints - sliding vs. lifting of an object (SL test). In normal the training of SL task was the easiest one, whereas the sS task was in some animals much more difficult than the SS task, and in others equivalent to this task. Removals in dorsolateral prefrontal cortex were made: total, only principalis sulcus, and only the rest of the area. Total and principalis lesions produced a severe impairment of all three tasks, while the third lesion produced only a slight deficit. The character of the impairment in the first two groups largely depended on the order in which the animals learned the three tasks in the pre-operative training.

Animals↗