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Biomedical subjects

C J Winstein

Publications and source records attributed to C J Winstein.

At least 19 recordsLinked to original sources
PubMed2006

Contralateral cerebellar damage impairs imperative planning but not updating of aimed arm movements in humans.

The specific motor control processes supported by the cerebellum and impaired with cerebellar damage remain unclear. The cerebellum has been implicated in both planning and updating of accurate movements. Previously, we used a statistical model to parcel aiming performance that was constrained by a timed-response paradigm into contributions attributed to a specified plan and feedforward updating. Here, we apply this procedure to determine the putative role of the cerebellum in planning and updating goal-directed aiming by comparing the performance of subjects with unilateral cerebellar stroke to controls. Subjects rapidly moved to targets in predictable or unpredictable conditions and cerebellar subjects used the contralesional limb to control for ipsilesional motor execution deficits. Displacement-derived movement velocity was used in the statistical model to determine the effect of planning and updating on accuracy. Compared to controls, the cerebellar group demonstrated errors in final position that were primarily determined by planning deficits. This finding is manifest in four ways: Cerebellar subjects (1) were less accurate than controls in both predictable and unpredictable conditions; (2) they showed minimal benefit from increased preparation time for target amplitude specification; (3) with ample time to plan direction, wrong direction response frequency was greater; and (4) final position was minimally determined by the plan. Because these deficits were found contralesional to the moving limb, the cerebellum's role in planning is not lateralized to one hemisphere but rather our findings suggest that cerebellar output affects motor planning for both upper limbs. Indeed, a lesion analysis showed that the dentate nucleus, an area implicated in planning motor strategies and the primary cerebellar output nucleus, was the only common region affected by our patient group with contralateral cerebellar strokes.

Acoustic Stimulation↗
PubMed2005

The co-ordination of bimanual rapid aiming movements following stroke.

OBJECTIVE: To determine the role of anticipatory and movement control processes for the coordination of bimanual target aiming in individuals post stroke. SUBJECTS: Thirty adults with chronic stroke and 30 individuals without stroke history. DESIGN: A two-group (stroke, control) by two-aiming type (unimanual, bimanual) by two-limb (paretic, nonparetic; left, right for controls) design with repeated measures on the last two factors. OUTCOME MEASURES: Kinematic analyses of performance and psychometric measures of reaction time, movement time, peak resultant velocity, time to and after peak resultant velocity and interlimb timing for movement initiation and target impact. RESULTS: Compared with unimanual aiming, the nonparetic limb exhibited a prolonged movement time in the bimanual condition; the locus for prolongation was primarily in the deceleration phase. This adaptive response allowed for a nearly simultaneous (both limbs) target impact in 81% of trials. Compared with the unimanual condition, the nonparetic limb exhibited a lower peak velocity (10%) in the bimanual condition. Conversely, compared with the unimanual condition, the paretic limb exhibited a higher peak velocity (4%) in the bimanual condition. This disociation between limb and condition was observed for the stroke group but not the control group. CONCLUSIONS: The interlimb coordination that emerged for the stroke group revealed a complex and asymmetric contribution from each limb mediated through anticipatory and motor control processes. We suggest that this coordination may be harnessed for future bimanual intervention approaches to rehabilitation of upper limb function after stroke.

Adult↗
PubMed2001

Implicit motor-sequence learning in humans following unilateral stroke: the impact of practice and explicit knowledge.

Learning and memory are sub-served by two interrelated systems - explicit and implicit. Explicit memory involves facts, while one form of implicit memory involves perceptual-motor processes. The purpose of this series of experiments was to investigate the ability of individuals with stroke-related brain damage to demonstrate implicit motor-sequence learning and the relative impacts of (1) extended practice, or (2) explicit knowledge prior to practice. Implicit learning was severely impaired without explicit knowledge and even under conditions of extended practice. However, when explicit knowledge was provided prior to practice, participants with stroke demonstrated implicit motor-sequence learning. These data suggest that following unilateral stroke, providing explicit information about the task and sequence can attenuate implicit motor learning deficits.

Adult↗
PubMed2001

Function of the 'direct' and 'indirect' pathways of the basal ganglia motor loop: evidence from reciprocal aiming movements in Parkinson's disease.

The purpose of this study was to test the validity of a neural-network model of the basal ganglia developed by Bischoff and colleagues (A. Bischoff, Modeling the basal ganglia in the control of arm movements (Doctoral dissertation, University of Southern California, 1998). Dissertation Abstr. Int. 59-08B (1998) 3924, 0208; A. Bischoff, M.A. Arbib, Modeling the role of basal ganglia and supplementary motor areas in sequential arm movements, Abstr. Soc. Neurosci. 23 (1997) 466; A. Bischoff, M.A. Arbib, C.J. Winstein, Modeling the role of the basal ganglia in reciprocal aiming task, Proceedings of the Fourth Annual Joint Symposium on Neural Computation, University of Southern California, Los Angeles, 7, 1997, pp. 20-27), and to examine the effects of levodopa on aiming movement performance. Findings confirm the model predictions for repetitive aiming movements. Individuals with late stage Parkinson's disease demonstrated longer movement times and longer pauses between aiming sequences compared to controls. Levodopa only slightly improved bradykinesia but not akinesia in these patients.

Adult↗
PubMed2000

Influence of central set on anticipatory and triggered grip-force adjustments.

The effects of predictability of load magnitude on anticipatory and triggered grip-force adjustments were studied as nine normal subjects used a precision grip to lift, hold, and replace an instrumented test object. Experience with a predictable stimulus has been shown to enhance magnitude scaling of triggered postural responses to different amplitudes of perturbations. However, this phenomenon, known as a central-set effect, has not been tested systematically for grip-force responses in the hand. In our study, predictability was manipulated by applying load perturbations of different magnitudes to the test object under conditions in which the upcoming load magnitude was presented repeatedly or under conditions in which the load magnitudes were presented randomly, each with two different pre-load grip conditions (unconstrained and constrained). In constrained conditions, initial grip forces were maintained near the minimum level necessary to prevent pre-loaded object slippage, while in unconstrained conditions, no initial grip force restrictions were imposed. The effect of predictable (blocked) and unpredictable (random) load presentations on scaling of anticipatory and triggered grip responses was tested by comparing the slopes of linear regressions between the imposed load and grip response magnitude. Anticipatory and triggered grip force responses were scaled to load magnitude in all conditions. However, regardless of pre-load grip force constraint, the gains (slopes) of grip responses relative to load magnitudes were greater when the magnitude of the upcoming load was predictable than when the load increase was unpredictable. In addition, a central-set effect was evidenced by the fewer number of drop trials in the predictable relative to unpredictable load conditions. Pre-load grip forces showed the greatest set effects. However, grip responses showed larger set effects, based on prediction, when pre-load grip force was constrained to lower levels. These results suggest that anticipatory processes pertaining to load magnitude permit the response gain of both voluntary and triggered rapid grip force adjustments to be set, at least partially, prior to perturbation onset. Comparison of anticipatory set effects for reactive torque and lower extremity EMG postural responses triggered by surface translation perturbations suggests a more general rule governing anticipatory processes.

Adult↗
PubMed2000

Impaired direction and extent specification of aimed arm movements in humans with stroke-related brain damage.

The role of sensorimotor (S-M) areas in the specification of kinematic parameters for aiming movements was studied by comparing the performance of six subjects with unilateral stroke to that of matched control subjects. Rapid arm movements were made to one of four targets by rotating the forearm in a short (20 degrees) or long (45 degrees) arc of motion. Thus, the four targets represented two directions (flexion or extension) and two extents (short or long). Subjects with stroke used the arm ipsilateral to the side of the lesion. A timed-response paradigm was used to dissociate response initiation and specification. Subjects initiated movements in concert with the last of four regularly timed tones. A visual cue of the designated target was presented during the preparation interval (400-0 ms) before the last tone. Targets were presented in a fixed sequence (predictable condition) or a random sequence (unpredictable condition). No significant differences in performance were found between stroke and control groups in the predictable condition. In the unpredictable condition, subjects with stroke produced more direction errors and were less accurate in extent than the control subjects. As specification time increased to 400 ms, the frequency of direction errors attenuated less for stroke than for control groups, but the reduction in magnitude of extent errors was similar for the two groups. When specification was minimal (i.e., <100 ms), default responses were distributed equally between directions and clustered around the short extent. Further, wrong direction responses did not converge on the designated extent as specification time increased. This pattern of findings is consistent with a view of parameterization of planning and executing movements, in which direction and extent can be specified in parallel. Our results suggest that ipsilateral S-M areas contribute to the specification of an optimal motor program, particularly when imperative programming of unimanual goal-directed aiming movements is required.

Acoustic Stimulation↗
PubMed2000

Deficits in compensatory trajectory adjustments after unilateral sensorimotor stroke.

In a previous study, we demonstrated that the time-course for amplitude specification of goal-directed aiming movements is similar for individuals with and without a unilateral sensorimotor (SM) area lesion. However, subjects with a SM lesion performing with the arm ipsilateral to the side of the brain lesion were significantly less accurate than control subjects in an unpredictable condition. The unpredictable condition requires that subjects both formulate an initial plan for movement as well as adjust the response later as additional information about the target (i.e., the goal) is gained. It has been demonstrated that premovement planning and compensatory adjustments are the processes contributing largely to accuracy in targeted, isometric force responses. A statistical model has been described, which partitions response trajectories into the planned and compensatory adjustment components. The purpose of this study was to apply the statistical model to our previous data to determine if the difference in accuracy in those with unilateral stroke was due to a deficit in premovement planning, compensatory adjustments, or a combination of these two factors. We compared the performance of six subjects with unilateral stroke to that of matched control subjects participating in a timed-response movement paradigm. Subjects rapidly flexed or extended the forearm in order to capture a short (20 degrees) or long (45 degrees) target presented in either a fixed (predictable condition) or a random sequence (unpredictable condition). For individuals with stroke, the limb used was that ipsilateral to the side of the SM lesion. Time to prepare the response was manipulated by varying the time of target presentation relative to an auditory cue for movement initiation. Velocity was derived from the displacement data, and multiple regression was used to determine the effect of premovement planning and compensatory adjustments on end-point accuracy. In the predictable condition, premovement planning contributed to final position more for the subjects with stroke [mean (SEM) = 0.50 (0.02)] than for the control subjects [0.36 (0.03)]. In the unpredictable condition, there were no differences between groups in percent variance due to planning [0.54 (2.1) for the stroke group and 0.45 (2.8) for the control group]. This suggests that the ipsilateral (i.e., intact, undamaged) SM hemisphere significantly participates in the premovement planning of an aiming action. In contrast, for both predictable and unpredictable conditions, compensatory adjustments accounted for a smaller percentage of the variability in final position for the subjects with stroke than for the control subjects [0.09 (2.2) for the stroke group and 0.25 (4.8) for the control group]. Therefore, the less accurate responses for the stroke group can be explained by deficits in the compensatory adjustment component. This suggests a substantial role for SM areas in the preparation and implementation of corrective actions while the effects of the pre-planned action are unfolding. In particular, we discuss the role of the ipsilateral SM areas in relation to parallel feedforward processing in unimanual aiming.

Aged↗
PubMed1999

Practice effects on the less-affected upper extremity after stroke.

OBJECTIVE: To test the hypotheses that (1) adults who have had a stroke, using the less affected upper extremity (UE), improve performance of an aiming task with practice, and (2) compared with control subjects, stroke patients show less improvement in a complex condition. DESIGN: Movement time (MT) and kinematic data were collected over practice. Comparisons were made between the less-affected UE of stroke patients and the same hand of controls. SETTING: A human performance laboratory. PARTICIPANTS: A matched sample of right-handed adults, 10 with unilateral stroke and 10 nondisabled controls. INTERVENTION: Practice of an aiming task in an easy and complex condition as defined by target width and distance between two targets. MAIN OUTCOME MEASURES: MT, peak velocity, and temporal phases of the trajectory. RESULTS: Adults who had experienced a stroke had persistently longer MTs than control subjects; however, all participants achieved faster MTs with practice in both conditions. The absolute amount of time in each temporal phase decreased without a change in the relative times. Peak velocity increased only in the easy condition. CONCLUSIONS: Adults with stroke damage can improve motor performance of the less-affected UE with practice. Further study is needed to see if practice effects are permanent and generalizable.

Cerebrovascular Disorders↗
PubMed1999

Motor learning after unilateral brain damage.

Forty adults, post-stroke from anterior circulation unilateral cerebrovascular accident (approximately 2 years post onset) and 40 age-matched controls (M = 57 years) practiced a rapid, spatially and temporally constrained programmed action under one of two augmented feedback practice conditions. Participants in the stroke group used the upper limb ipsilateral to the lesion. After an extended practice period (198 trials), acquisition, retention, and reacquisition performance was assessed for accuracy and consistency and compared over trials, between groups and feedback conditions. Both stroke and control groups demonstrated significant improvement in accuracy and consistency over practice with relative persistence of these changes during retention. There were no differences between groups (stroke vs control) in performance patterns across trials for acquisition, retention, or reacquisition phases. In addition, there were no differential effects of the two augmented feedback conditions on performance and no interactions of feedback condition with group. However, independent of feedback condition, the stroke group performed with more error than did the control group during all experimental phases (i.e., acquisition, retention, reacquisition). These results suggest that unilateral stroke-related damage in the sensorimotor areas primarily effects the processes underlying the control and execution of motor skills but not the learning of those skills. Implications of these findings for physical rehabilitation are discussed.

Adult↗
PubMed1997

Motor task difficulty and brain activity: investigation of goal-directed reciprocal aiming using positron emission tomography.

Differences in the kinematics and pattern of relative regional cerebral blood flow (rCBF) during goal-directed arm aiming were investigated with the use of a Fitts continuous aiming paradigm with three difficulty conditions (index of difficulty, ID) and two aiming types (transport vs. targeting) in six healthy right-handed young participants with the use of video-based movement trajectory analysis and positron emission tomography. Movement time and kinematic characteristics were analyzed together with the magnitude of cerebral blood flow to identify areas of brain activity proportionate to task and movement variables. Significant differences in rCBF between task conditions were determined by analysis of variance with planned comparisons of means with the use of group mean weighted linear contrasts. Data were first analyzed for the group. Then individual subject differences for the movement versus no movement and task difficulty comparisons were related to each individual subjects' anatomy by magnetic resonance imaging. Significant differences in rCBF during reciprocal aiming compared with no-movement conditions were found in a mosaic of well-known cortical and subcortical areas associated with the planning and execution of goal-directed movements. These included cortical areas in the left sensorimotor, dorsal premotor, and ventral premotor cortices, caudal supplementary motor area (SMA) proper, and parietal cortex, and subcortical areas in the left putamen, globus pallidus, red nucleus, thalamus, and anterior cerebellum. As aiming task difficulty (ID) increased, rCBF increased in areas associated with the planning of more complex movements requiring greater visuomotor processing. These included bilateral occipital, left inferior parietal, and left dorsal cingulate cortices--caudal SMA proper and right dorsal premotor area. These same areas showed significant increases or decreases, respectively, when contrast means were compared with the use of movement time or relative acceleration time, respectively, as the weighting factor. Analysis of individual subject differences revealed a correspondence between the spatial extent of rCBF changes as a function of task ID and the individuals' movement times. As task ID decreased, significant increases in rCBF were evident in the right anterior cerebellum, left middle occipital gyrus, and right ventral premotor area. Functionally, these areas are associated with aiming conditions in which the motor execution demands are high (i.e., coordination of rapid reversals) and precise trajectory planning is minimal. These same areas showed significant increases or decreases, respectively, when contrast means were compared with the use of movement time or relative acceleration time, respectively, as the weighting factor. A functional dissociation resulted from the weighted linear contrasts between larger (limb transport) or smaller (endpoint targeting) type amplitude/target width aiming conditions. Areas with significantly greater rCBF for targeting were the left motor cortex, left intraparietal sulcus, and left caudate. In contrast, those areas with greater rCBF associated with limb transport included bilateral occipital lingual gyri and the right anterior cerebellum. Various theoretical explanations for the speed/accuracy tradeoffs of rapid aiming movements have been proposed since the original information theory hypothesis of Fitts. This is the first report to relate the predictable variations in motor control under changing task constraints with the functional anatomy of these rapid goal-directed aiming movements. Differences in unimanual aiming task difficulty lead to dissociable activation of cortical-subcortical networks. Further, these data suggest that when more precise targeting is required, independent of task difficulty, a cortical-subcortical loop composed of the contralateral motor cortex, intraparietal sulcus, and caudate is activated. This is consistent with the role of motor cortex

Adult↗
PubMed1996

The locus of age-related movement slowing: sensory processing in continuous goal-directed aiming.

Prolonged movement times in elderly persons have been well documented; however, the locus of this slowing is uncertain. Kinematic analysis of discrete aiming has revealed deficits primarily in the target approach phase, suggesting inefficient feedback processing. This study investigated age-related movement slowing in a continuous aiming task, for which movements are mediated by feedforward and on-line sensory processes. Two-dimensional video-recordings were made of young and elderly adults performing reciprocal tapping using the right and left hands under three different accuracy conditions. The elderly subjects exhibited more discrete adjustments in the trajectories coupled with longer times in this period. Further, the elderly spent more time reversing direction between target hits, especially in the high accuracy condition. Longer time on target was seen in the left-hand performance of the elderly. Results suggest that the locus of age-related slowing in the performance of continuous aiming may reflect a greater dependence on slower feedback processes instead of rapid, on-line, and feedforward sensory processes. Age-related differences in hand performance may provide further insight into central processing deficits.

Adult↗
PubMed1996

Learning a partial-weight-bearing skill: effectiveness of two forms of feedback.

BACKGROUND AND PURPOSE: Partial weight bearing (PWB) is a skill commonly taught by physical therapists. This study compared the effects of practice with either augmented feedback provided during the task (concurrent feedback) or augmented feedback provided after the task (postresponse feedback) for the learning of PWB with crutches. SUBJECTS: Sixty young adults without known impairment of the neuromusculoskeletal system volunteered for the study. METHODS: Subjects practiced supporting 30% of body weight while stepping onto a floor scale. Augmented feedback was provided during each trial for the concurrent feedback group and either following each trial or after every five trials for the postresponse feedback groups. Subjects returned 2 days later for a no-feedback retention test. RESULTS: During practice, the concurrent feedback group was more accurate and consistent than either of the postresponse feedback groups. During retention, however, the postresponse feedback groups were the most accurate; all groups were equally consistent during retention. CONCLUSION AND DISCUSSION: These results suggest that practice with concurrent feedback is beneficial for the immediate performance but not for the learning of this sensorimotor skill.

Adult↗
PubMed1995

Effects of unilateral brain damage on the control of goal-directed hand movements.

Insight into the functional neural substrates associated with the control of goal-directed purposive movements can be obtained through the study of the performance of individuals with brain damage. The control of rapid reciprocal aiming was investigated by comparing ipsilateral limb performance of subjects with unilateral brain damage to that of controls performing with the same limb. Thirty right-hand-dominant individuals, ten with right hemisphere stroke, ten with left hemisphere stroke, and ten age-matched controls performed unconstrained alternating tapping movements under three conditions of task complexity. The path of the stylus was recorded by video using two-dimensional kinematic techniques. Key kinematic features of the vertical and horizontal components of the trajectories were analyzed using both quantitative and qualitative methods. All subjects with brain damage showed prolonged movement times; however, the locus of the slowing depended on lesion side. Specifically, subjects with left stroke showed deficits in the open-loop component of the movement across all three conditions of task complexity, and a prolonged reversal phase surrounding target impact, particularly in the most complex condition. In contrast, subjects with right stroke showed deficits in the closed-loop phase of the movement prior to target impact, particularly in the most complex condition when visual information was necessary for accuracy. Together, these results suggest that for the control of rapid goal-directed aiming movements, the left hemisphere is dominant for task-relevant aspects of processing associated with the ballistic component and the timing or triggering of sequential movements. In contrast, the right hemisphere is dominant for processing associated with rapid, on-line visual information even when target location is known and direction is certain.

Aged↗
PubMed1994

Effects of physical guidance and knowledge of results on motor learning: support for the guidance hypothesis.

The guidance hypothesis (Schmidt, 1991) predicts that the guiding properties of augmented feedback are beneficial for motor learning when used to reduce error, but detrimental when relied upon. Therefore, a heavily guiding form of feedback might be detrimental for learning. In addition, the guidance hypothesis predicts that practice with a high relative frequency of augmented feedback would be detrimental for learning. An experiment is described that crossed two forms of feedback with two levels of relative frequency. Subjects practiced movements to a target with either physical guidance or knowledge of results, and with either a high or faded relative frequency. The high frequency physical guidance condition resulted in the poorest retention, and both high frequency feedback conditions resulted in the least accuracy in transfer. These results provide support for the guidance hypothesis and suggest consideration of the combined effects on learning of the type and relative frequency of augmented feedback and acquisition-test conditions.

Adult↗
PubMed1991

Influences of object weight and instruction on grip force adjustments.

This study investigated the influence of object weight and instructions on grip force responses in humans. Using a precision grip, subjects lifted a small instrumented test object to a predetermined height. Prior to each set of 40 trials, subjects were verbally instructed to either "hold" or "let go" of the object in response to any change in weight. Unpredictably on some trials (less than 20%), a sudden sustained increase (load) or decrease (unload) in vertical load was applied to the object. Grip responses to these induced weight changes were evaluated by measuring grip force, object position, and associated electromyographic (EMG) activity. Grip force changes for a load were over three times greater than those for an unload. Such asymmetry may reflect everyday grasp and manipulation in a gravity-influenced world. Grip force adjustments to loads following "hold" instructions were on the average somewhat larger than those following "let go" instructions, but there was no influence of instructions on responses to unloads. These findings contrast with more robust influences of verbal instruction on automatic postural and proximal upper limb responses and also may suggest that grip force adjustments are influenced to a greater extent by intrinsic task variables than by extrinsic volitional intent. Such organization appears tailored to functional task requirements in natural environmental contexts.

Adult↗
PubMed1991

Knowledge of results and motor learning--implications for physical therapy.

Relevant to this special series on movement science, a brief overview of research in the field of motor learning is provided. A distinction between learning and performance is emphasized with respect to experimental design and the evaluation of laboratory and clinical intervention techniques. Intrinsic and extrinsic feedback are defined. Basic principles of motor learning pertaining to the use of augmented feedback or knowledge of results (KR) are reviewed. Particular emphasis is placed on recent research regarding the effects of selected KR variations (KR relative frequency, bandwidth KR, and KR delay) on motor performance and learning in healthy young adults. Results are discussed in terms of short-lasting temporary performance effects and relatively long-lasting learning effects. Theoretical and practical implications from this research are discussed. It is suggested that it is appropriate to use the principles obtained through laboratory experimentation as guidelines rather than as exact recommendations when applying basic research findings to clinical practice.

Feedback↗
PubMed1989

Qualitative dynamics of disordered human locomotion: a preliminary investigation.

A qualitative approach to the evaluation of disordered locomotion is introduced within the framework of dynamical systems theory. Exemplar phase plane and angle-angle plots of knee and ankle movements were constructed from limb trajectories of neurologically impaired individuals and qualitatively compared with similar plots, reflecting normal locomotion. In phase plane trajectories of normal locomotion, characteristics of spring-like dynamics dominated the loading and unloading phases whereas those of ballistic pendular dynamics were seen during swing. The overall squareness of the normal phase plane trajectories suggested precisely timed and narrowly focused controls. in contrast, phase plane records from hemiparetic subjects had markedly reduced segmental velocities, pronounced velocity reversals in both stance and swing, and a loss of overall squareness. Knee-ankle plots of normal locomotion revealed important features of intersegmental coordination such as coupled out-of-phase coordination in loading and unloading, a decoupled phase offset in early swing, and a kind of active partitioning in late swing in which one segment moved while the other remained constant. These intersegmental relations were absent or distorted in the hemiparetic angle-angle plots. It is suggested that this qualitative approach, together with electromyography and force dynamics, may allow the characterization of the movement disorders associated with given neuropathologies.

Journal Article↗