Parallel stages of learning and recovery of skilled reaching after motor cortex stroke: "oppositions" organize normal and compensatory movements

Forelimb/hand motor cortex injury in rodents and primates causes impairments in skilled paw/hand movements that includes a period of movement absence followed by functional recovery/compensation. Although the postsurgical period of movement absence has been attributed to "shock" or "diaschisis", the behavior of animals during this period has not been fully described. Here, rats were trained to reach for single food pellets from a shelf and then the vasculature of the forelimb region of the sensorimotor cortex contralateral to the reaching limb was removed. A control group received a posterior parietal cortex devasularization. Frame-by-frame video analysis of reaching behavior showed that the stages of the acquisition of skilled reaching and the stages of recovery after motor cortex stroke were similar. The animals sequentially learn three relationships or "oppositions" between a body part and the food target. The oppositions are invariant relationships but each can be achieved with movements that can vary from reach to reach and between rats. A snout-pellet opposition organizes the movements of orienting, a paw-pellet opposition organizes limb transport and grasping the pellet in the digits, and a mouth-pellet opposition organizes limb withdrawal and the release of the food into the mouth. The three oppositions and the movements that they recruit were disrupted after motor cortex damage, but not parietal cortex damage. The oppositions were reestablished after stroke in the order in which they were acquired prior to stroke. Enduring impairments were more noticeable in transport and withdrawal oppositions. That the stages of recovery from motor cortex stroke parallel those of initial acquisition are discussed in relation to contemporary explanations of diaschisis and the contribution of motor cortex to motor learning.     

Intensive sensorimotor arm training mediated by therapist or robot improves hemiparesis in patients with chronic stroke

Investigators have demonstrated that a variety of intensive movement training protocols for persistent upper limb paralysis in patients with chronic stroke (6 months or more after stroke) improve motor outcome. This randomized controlled study determined in patients with upper limb motor impairment after chronic stroke whether movement therapy delivered by a robot or by a therapist using an intensive training protocol was superior. Robotic training (n = 11) and an intensive movement protocol (n = 10) improved the impairment measures of motor outcome significantly and comparably; there were no significant changes in disability measures. Motor gains were maintained at the 3-month evaluation after training. These data contribute to the growing awareness that persistent impairments in those with chronic stroke may not reflect exhausted capacity for improvement. These new protocols, rendered by either therapist or robot, can be standardized, tested, and replicated, and potentially will contribute to rational activity-based programs.     

镜像训练引导的运动想象疗法对急性缺血性脑卒中偏瘫患者上肢功能的康复效果

目的:本研究旨在对镜像训练引导的运动想象疗法是否能够更有效地改善急性缺血性脑卒中后偏瘫患者的上肢功能以及日常生活能力进行评价。方法:研究对象为2014年1月1日—2016年6月30日符合病例选择标准的76例急性缺血性脑卒中后偏瘫患者。将76例患者随机分入镜像训练引导的运动想象疗法组(38例)和单纯的运动想象疗法组(38例),在常规康复训练的基础上,分别接受镜像训练引导的运动想象疗法和单纯的运动想象疗法,共治疗4周。对2组治疗前后的美国国立卫生研究院卒中量表(National Institute of Health Stroke Scale,NIHSS)评分、Barthel指数、上肢动作研究量表(Action Research Arm Test,ARAT)评分和Fugl-Meyer上肢运动功能评分进行比较。结果:2组患者治疗后的NIHSS评分、Barthel指数、ARAT评分和Fugl-Meyer上肢运动功能评分均较治疗前显著改善(P值均0.05)。镜像训练引导的运动想象疗法组治疗后的NIHSS评分、Barthel指数、ARAT评分和Fugl-Meyer上肢运动功能评分的改善幅度均显著大于单纯的运动想象疗法组(P值均0.05)。结论:镜像训练引导的运动想象疗法应用于急性缺血性脑卒中后偏瘫患者上肢功能的康复治疗,与单纯的运动想象疗法相比,可以更好地改善患者的上肢功能和生活自理能力。     

Clinical spectrum of movement disorders after stroke in childhood and adulthood

Although rare, many different types of hyperkinetic and hypokinetic movement disorders have been described after both ischemic and hemorrhagic stroke in children and in adults. Current knowledge about these disorders comes from single case reports or small series of cases compiled from retrospective studies. Data from hospital-based studies suggest a prevalence of poststroke movement disorders ranging from 1.1 to 3.9%. However, despite the development of emergency care for stroke, these clinical syndromes remain insufficiently recognized. Poststroke movement disorders take place in the acute phase or following a variable delay after stroke onset, and could be transient or persistent. Dystonia is the most frequent movement disorder, occurring after a delay of several months, while chorea and hemiballism are most frequent in the acute stages. Amongst transient movement disorders, limb shaking is associated with high-grade stenosis or occlusion of the internal carotid artery, while myoclonus and asterixis are rare. From a pathophysiological point of view, most of these symptoms are induced by a lesion involving the basal ganglia, the thalamus, or the frontal subcortical pathways. In this article, we updated the clinical spectrum, neuropathophysiological mechanisms, and prognosis of stroke-induced movement disorders in adults and children.     

Attempt-dependent decrease in skilled reaching characterizes the acute postsurgical period following a forelimb motor cortex lesion: an experimental demonstration of learned nonuse in the rat

The notion that shock or diaschisis is a distinctive stage in the recovery process following brain damage has played a formative role in the characterization of brain injury. For example, damage to the forelimb region of motor cortex results in an acute period of behavioural depression in skilled reaching and other skilled actions followed by improved performance mediated by compensatory movements. Whereas the progression of improvement and the use of compensatory movements in the chronic period of recovery is well-documented, temporal aspects of behaviour during the acute period of depression of behaviour are relatively unstudied. The present study examined the temporal scheduling of reach-attempts by rats attempting to gain single pellets of food from a shelf in a skilled reaching task. Pretrained rats received contralateral-to-the-pretrained limb forelimb motor cortex lesions. Control lesions included contralateral-to-the-pretrained limb parietal cortex lesions, or ipsilateral-to-the-pretrained limb motor cortex lesions. Frame-by-frame video analysis of behaviour showed a decrease in reaching attempts as a function of successive approaches and attempts to grasp the food over the first few postsurgical days in rats with contralateral-to-the-pretrained limb motor cortex lesions. A similar approach-dependent decrease in attempts did not occur after parietal or ipsilateral-to-the-pretrained limb motor cortex lesions. The decrease in responding occurred only during acute testing and was not observed in rats first tested after 8 days of postoperative recovery. The findings are discussed in relation to the ideas that: (1) the stroke subject is an active participant in modifying behaviour to cope with injury; (2) learned nonuse contributes to behaviour in the acute postinjury period following motor cortex injury; (3) diaschisis inadequately accounts for poststoke behaviour.     

Neuronal injury in the motor cortex after chronic stroke and lower limb motor impairment: a voxelbased lesion symptom mapping study

Many studies have examined motor impairments using voxel-based lesion symptom mapping, but few are reported regarding the corresponding relationship between cerebral cortex injury and lower limb motor impairment analyzed using this technique. This study correlated neuro- nal injury in the cerebral cortex of 16 patients with chronic stroke based on a voxel-based lesion symptom mapping analysis. Neuronal injury in the corona radiata, caudate nucleus and putamen of patients with chronic stroke could predict walking speed. The behavioral measure scores were consistent with motor deficits expected after damage to the cortical motor system due to stroke. These findings suggest that voxel-based lesion symptom mapping may provide a more accurate prognosis of motor recovery from chronic stroke according to neuronal injury in cerebral motor cortex.     

Clinical Prediction Rule for Identifying the Stroke Patients who will Obtain Clinically Important Improvement of Upper Limb Motor Function by Robot-Assisted Upper Limb

BackgroundThe number of studies on the characteristics of patients with stroke who would benefit from robot-assisted upper limb rehabilitation is limited, and there are no clear criteria for determining which individuals should receive such treatment. The current study aimed to develop a clinical prediction rule using machine learning to identify the characteristics of patients with stroke who can the achieve minimal clinically important difference of the Fugl-Meyer Upper Extremity Evaluation (FMA-UE) after single-joint hybrid assistive limb (HAL-SJ) rehabilitation.MethodsThis study included 71 patients with subacute stroke who received HAL-SJ rehabilitation. The chi-square automatic interaction detector (CHAID) model was applied to predict improvement in upper limb motor function. Based the analysis using CHAID, age, sex, days from stroke onset to the initiation of HAL-SJ rehabilitation, and upper limb motor and cognitive functions were used as independent variables. Improvement in upper limb motor function was determined based on the minimal clinically important difference of the FMA-UE, which was used as a dependent variable.ResultsAccording to the CHAID model, the FMA-UE score during the initiation of HAL-SJ rehabilitation was the most significant predictive factor for patients who are likely to respond to the intervention. Interestingly, this therapy was more effective in patients with moderate upper limb motor dysfunction and early initiation of HAL-SJ rehabilitation. The accuracy of the CHAID model was 0.89 (95% confidence interval: 0.81–0.96).ConclusionWe developed a clinical prediction rule for identifying the characteristics of patients with stroke whose upper limb motor function can improve with HAL-SJ rehabilitation.     

Neuroplasticity,learning and recovery after stroke: A critical evaluation of constraint-induced therapy

Constraint-induced movement therapy (CIMT) has been hailed as a radical new approach to stroke rehabilitation. The guiding theory is that impairment of hand function is exacerbated by learned non-use and that this in turn leads to a loss of cortical representation of the upper limb. It is claimed that these processes can be reversed by two weeks of constraint of the unaffected limb combined with intensive practice in use of the paretic hand, and numerous small-scale studies have suggested that CIMT can lead to large improvements in function more than a year after stroke. However, the theory of learned non-use is open to question and there is uncertainty about the nature of the improvements induced by CIMT. The greatest effect seems to be increased spontaneous use of the hand, either through reduction of learned non-use or by overcoming the sense of effort during movement. There is also evidence of some improvement on dexterity tests but no studies have analysed in detail whether this reflects reduction of basic motor impairment or learning of compensatory movement strategies. The current weight of evidence is in favour of compensatory learning. Cortical changes detected by transcranial magnetic stimulation (TMS) or functional imaging may reflect this compensatory motor skill learning rather than restoration of representations lost due to the infarct or non-use of the limb. If future studies confirm this then the clinical implication is that direct teaching of unimanual or bimanual compensatory strategies might be a more productive approach than constraint.     

Neuroplasticity, learning and recovery after stroke: a critical evaluation of constraint-induced therapy

Constraint-induced movement therapy (CIMT) has been hailed as a radical new approach to stroke rehabilitation. The guiding theory is that impairment of hand function is exacerbated by learned non-use and that this in turn leads to a loss of cortical representation of the upper limb. It is claimed that these processes can be reversed by two weeks of constraint of the unaffected limb combined with intensive practice in use of the paretic hand, and numerous small-scale studies have suggested that CIMT can lead to large improvements in function more than a year after stroke. However, the theory of learned non-use is open to question and there is uncertainty about the nature of the improvements induced by CIMT. The greatest effect seems to be increased spontaneous use of the hand, either through reduction of learned non-use or by overcoming the sense of effort during movement. There is also evidence of some improvement on dexterity tests but no studies have analysed in detail whether this reflects reduction of basic motor impairment or learning of compensatory movement strategies. The current weight of evidence is in favour of compensatory learning. Cortical changes detected by transcranial magnetic stimulation (TMS) or functional imaging may reflect this compensatory motor skill learning rather than restoration of representations lost due to the infarct or non-use of the limb. If future studies confirm this then the clinical implication is that direct teaching of unimanual or bimanual compensatory strategies might be a more productive approach than constraint.     

Impaired interlimb coordination is related to asymmetries during pedaling after stroke

ObjectiveTo understand whether lower limb asymmetry in chronic stroke is related to paretic motor impairment or impaired interlimb coordination.MethodsStroke and control participants performed conventional, unilateral, and bilateral uncoupled pedaling. During uncoupled pedaling, the pedals were mechanically disconnected. Paretic mechanical work was measured during conventional pedaling. Pedaling velocity and muscle activity were compared across conditions and groups. Relative limb phasing was examined during uncoupled pedaling.ResultsDuring conventional pedaling, EMG and mechanical work were lower in the paretic than the non-paretic limb (asymmetry). During unilateral pedaling with the paretic limb, muscle activity was larger, but velocity was slower and more variable than during conventional pedaling (evidence of paretic motor impairment). During uncoupled pedaling, muscle activity increased further, but velocity was slower and more variable than in other conditions (evidence of impaired interlimb coordination). Relative limb phasing was impaired in stroke participants. Regression analysis suggested that interlimb coordination may be a stronger predictor of asymmetry than paretic motor impairment.ConclusionsParetic motor impairment and impaired interlimb coordination may contribute to asymmetry during pedaling after stroke.SignificanceRehabilitation that addresses paretic motor impairment and impaired interlimb coordination may improve symmetry and maximize improvement.     

肢体抖动性短暂性脑缺血发作临床分析

目的 通过3例典型患者的病史和辅助检查，结合文献复习，探讨肢体抖动性短暂性脑缺血发作的临床表现及诊断，以提高诊断的准确率。方法 采用动态脑电图、超声多普勒、磁共振成像、磁共振动脉血管造影、全脑血管造影等辅助检查，对3例肢体抖动性短暂性脑缺血发作患者进行临床表现、辅助检查及影像学资料分析。结果 3例患者均有肢体抖动的临床表现，其中2例曾被误诊为继发性癫痫，给予抗癫痫治疗无效，行全脑血管造影、脑电图等检查。全脑血管造影提示3例颈内动脉系统均存在严重闭塞或狭窄性病变，而发作期脑电图检查未见癫痫波释放。给予抗血小板聚集等药物治疗，但仍偶有发作。2例施行血管内支架植入术后发作完全停止，1例由于血管迂曲明显，手术未获成功，经内科保守治疗症状缓解出院。结论 肢体抖动性短暂性脑缺血发作为临床少见短暂性脑缺血发作，其发作形式常表现为发作性、无意识的一侧肢体无力及抖动，和局灶性运动性癫痫发作相似，易误诊为局灶性癫痫。通过脑电图及全脑血管造影等检查可以明确诊断，从而提高对该病诊断的准确率，防止漏诊及误诊。     

Motor evoked potentials in predicting recovery from upper extremity paralysis after acute stroke

OBJECTIVE: The use of motor evoked potentials (MEPs) in predicting recovery after stroke still appears to be somehow equivocal. We assessed the prognostic value of MEPs with respect to arm and hand motor recovery in acute stroke patients. METHODS: This cohort study included 43 consecutive acute stroke patients with complete paralysis of the upper extremity. MEPs of the abductor digiti minimi muscle (ADM) and the biceps brachii muscle (BB) were obtained within 10 days after stroke onset. The upper limb subset of the Fugl-Meyer Motor Assessment was used to evaluate the motor performance at regular intervals until 6 months after stroke. RESULTS: The follow-up was complete in 40 patients (2 patients died and 1 patient had a recurrent stroke); 14 patients showed motor recovery of the arm and their mean 26-week arm motor score was 17.93 (range 3-30, SD 11.68); hand motor recovery occurred in 11 patients and their mean 26-week hand motor score was 11.09 (range 4-14, SD 4.10). Stepwise logistic regression revealed prognostic models for both arm and hand motor recovery based on BB MEPs (odds ratio 7.69, confidence interval, CI, 1.16-50.95) and ADM MEPs (odds ratio 16.20, CI 2.51-104.40), respectively. CONCLUSIONS: The predictive significance of MEPs with respect to motor recovery of the upper extremity was obvious in our homogeneous sample of patients. This agrees with the paradigm that motor recovery after infarction is strongly dependent on a critical residual sparing of the corticospinal function. In this context, the test properties of MEPs in predicting motor recovery are discussed. The added value of MEPs with respect to motor recovery of the upper extremity should be regarded as established for patients with initial paralysis, especially since clinical examination alone lacks the possibility to detect the potential for motor recovery in these cases.     

Mapping Early Changes of Cortical Motor Output after Subcortical Stroke: A Transcranial Magnetic Stimulation Study

After acute stroke several changes in cortical excitability occur involving affected (AH) and unaffected hemisphere (UH) but whether they contribute to motor recovery is still controversial. We performed transcranial magnetic stimulation mapping of several upper limb muscles over the two hemispheres in thirteen patients at 4–12 days from subcortical stroke and after 1 month. The occurrence of mirror movements (MMs) on the healthy side during contraction of paretic muscles was measured. At baseline, cortical excitability parameters over the AH decreased in comparison with controls, while excitability over the UH increased correlating with severity of motor deficits of the affected arm at baseline as well as with poor recovery. At follow-up, map parameters of the UH became closer to those of controls independently from recovery, while for the AH the number of responsive sites increased significantly. Ipsilateral motor evoked responses (iMEPs) in the affected arm were never elicited. We observed an early impairment in dexterity of the ipsilesional hand that recovered over-time but persistently differed in comparison with controls. MMs occurrence increased at baseline correlating with reduced cortical excitability of the AH as well as with increased map density over the UH. The acute increased excitability of the UH after stroke has a negative prognostic value on recovery and negatively affects motor performance of the ipsilesional hand. Moreover, the absence of iMEPs and the normalization of motor cortical excitability at follow-up indicate that the UH primary motor area does not contribute to recovery.     

Robotic technology and stroke rehabilitation: translating research into practice

Research on the effectiveness of robotic therapy for the paretic upper limb after stroke has shown statistically significant reductions in motor impairment during both acute and chronic phases of recovery. Despite growing empirical support for this technology and a stronger focus on optimizing rehabilitation outcomes and productivity, there continues to be a disconnect between research and clinical practice. We review studies on the use of robot-aided neurorehabilitation for the paretic arm after stroke and discuss ways in which this technology may provide opportunities for intensive training that complement more conventional therapy methods.     

Limb apraxia in acute ischemic stroke: A neglected clinical challenge?

Symptoms of limb apraxia and executive dysfunctions are currently not explicitly considered by the National Institutes of Health Stroke Scale and, thus, not routinely tested by clinicians in the acute care of patients with suspected stroke. Neuropsychological testing, clinical examination, MRI, and functional magnetic resonance imaging (fMRI) were performed in a right-handed patient with acute onset of left-sided sensorimotor hemiparesis due to a right hemisphere ischemic stroke. Deficits in the execution of meaningless and meaningful gestures were not detected properly on initial clinical examination but were revealed later on through neuropsychological testing. Instead, the patient’s inability to respond to specific instructions in the acute care setting was mistaken to reflect severe deficits in auditory comprehension. fMRI revealed right-hemispheric localization of language in the right-handed patient. We suggest including a bedside test for limb apraxia symptoms in acute clinical care of stroke patients. The distinction between deficits in limb praxis and impairments of language can be complicated owing to the common hemispheric co-localization of the two functions.     

Relating MRI changes to motor deficit after ischemic stroke by segmentation of functional motor pathways

BACKGROUND AND PURPOSE: Infarct size on T2-weighted MRI correlates only modestly with outcome, particularly for small strokes. This may be largely because of differences in the locations of infarcts and consequently in the functional pathways that are damaged. To test this hypothesis quantitatively, we developed a "mask" of the corticospinal pathway to determine whether the extent of stroke intersection with the pathway would be more closely related to clinical motor deficit and axonal injury in the descending motor pathways than total stroke lesion volume. METHODS: Eighteen patients were studied > or =1 month after first ischemic stroke that caused a motor deficit by use of brain T2-weighted imaging, MR spectroscopic (MRS) measurements of the neuronal marker compound N-acetyl aspartate in the posterior limb of the internal capsule, and motor impairment and disability measures. A corticospinal mask based on neuroanatomic landmarks was generated from a subset of the MRI data. The maximum proportion of the cross-sectional area of this mask occupied by stroke was determined for each patient after all brain images were transformed into a common stereotaxic brain space. RESULTS: There was a significant linear relationship between the maximum proportional cross-sectional area of the corticospinal mask occupied by stroke and motor deficit (r(2)=0.82, P<0.001), whereas the relationship between the total stroke volume and motor deficit was better described by a cubic curve (r(2)=0.76, P<0.001). Inspection of the data plots showed that the total stroke volume discriminated poorly between smaller strokes with regard to the extent of associated motor deficit, whereas the maximum proportion of the mask cross-sectional area occupied by stroke appeared to be a more discriminatory marker of motor deficit and also N-acetyl aspartate reduction. CONCLUSIONS: Segmentation of functional motor pathways on MRI allows estimation of the extent of damage specifically to that pathway by the stroke lesion. The extent of stroke intersection with the motor pathways was more linearly related to the magnitude of motor deficit than total lesion volume and appeared to be a better discriminator between small strokes with regard to motor deficit. This emphasizes the importance of the anatomic relationship of the infarct to local structures in determining functional impairment. Prospective studies are necessary to assess whether this approach would allow improved early estimation of prognosis after stroke.     

Upper-limb discoordination in hemiparetic stroke: implications for neurorehabilitation

Clinically, upper-limb discoordination after stroke is evident in the form of stereotypic movement patterns that reflect a loss of independent joint control. These movement abnormalities, in conjunction with our recent quantitative findings under isometric conditions, provide evidence for an impaired capacity to generate certain muscle coactivation patterns in the impaired limb. In this article, we examine the parallels that exist between coordination disturbances observed under isometric and movement conditions. Our results suggest that discoordination in stroke may largely represent a manifestation of additional neural constraints on motor outflow. The neurotherapeutic implications of our findings are discussed.     

Effective anticonvulsant therapy in a patient with limb shaking: A case report

Abstract A case is described of a patient with limb shaking in whom anticonvulsant therapy was effective for inhibiting attacks. A 70 year old female developed rhythmical involuntary limb shaking of the right upper and lower limb in April 1986. She was diagnosed as having transient ischemic attacks and was followed up under treatment with an antiplatelet drug. Subsequently, anticonvulsant therapy was also initiated on an outpatient basis. In August 1991, she was admitted with shaking of the right upper and lower limbs. Low molecular dextran was ineffective for inhibiting limb shaking attacks, but intravenous injection of diazepam was effective. Phenytoin and phenobarbital was used in combination. No limb shaking attacks occurred thereafter. The involuntary movement was the same as that observed at the onset of the disease. Though no changes were observed in the pattern of the involuntary movement, anticonvulsant therapy was effective in preventing and inhibiting attacks. This finding is inconsistent with previous reports. It is possible that epileptic factors are involved in the development of this condition.     

Acute isolated capsular stroke. A clinical study of 148 cases

The objectives of the study were to assess differential features between capsular stroke of ischemic and hemorrhagic origin, and to compare capsular strokes with all other (non-capsular) strokes. Data of 148 patients with isolated capsular stroke were collected from a prospective hospital-based stroke registry in which 2000 consecutive acute stroke patients were included. Isolated capsular stroke accounted for 8.4% of strokes included in the registry (8.4% of ischemic strokes and 10.5% of intracerebral hemorrhages). Capsular stroke of hemorrhagic origin (n = 24) was more severe than ischemic capsular stroke (n = 124) as determined by a significantly higher in-hospital mortality, length of stay, and lower number of patients free of functional deficit at discharge. After multivariate analysis, limb weakness, sudden onset, and sensory symptoms were independently associated with capsular hemorrhage, whereas pure motor hemiparesis appeared to be associated with capsular infarction. In summary, one of each 12 patients with acute ischemic stroke and one of each 10 patients with acute intracerebral hemorrhage had an isolated capsular stroke. Lacunar syndrome was the most frequent clinical presentation being more common (particularly pure motor hemiparesis) in ischemic than in hemorrhagic capsular stroke. Capsular hemorrhage and capsular infarction showed identical risk factor profiles suggesting the same underlying vascular pathology for both conditions.     

Constraint therapy versus intensive training: Implications for motor control and brain plasticity after stroke

Many studies have demonstrated that constraint induced movement therapy (CIMT) improves upper limb motor impairment following stroke. This rehabilitation method combines constraint of the less-affected upperlimb with intensive training of the paretic limb. The aim of the present study was to evaluate, in a single case study, the respective effects of each of these two therapeutic interventions. The patient selected was a 32-year-old right-handed woman. Three and a half years prior to inclusion, she suffered a left capsular infarct responsible for a right hemiparesis. Several assessments were carried out before and after constraint therapy and then after intensive training. Each assessment included measures of hand function as well as a three-dimensional (3D) analysis of prehension. Results showed a significant improvement of motor performance after the constraint period and an additional amelioration after the intensive training period. Kinematic analysis showed that the transport phase of movement (movement time and velocity peaks) was improved after the constraint period, whereas the grasping phase (maximum grip aperture) was modified after intensive training. These data could reflect a specific effect of treatment on each phase of the prehension task, or a more general proximal-to-distal gradient of recovery. Although firm conclusions are not warranted on the basis of this single case study, we confirm the utility of 3D motion analysis to evaluate objectively the effectiveness of a therapeutic intervention. We also discuss the implications of our findings for understanding processes of motor control reorganisation.