Recovery of motor function after stroke

The human brain possesses a remarkable ability to adapt in response to changing anatomical (e.g., aging) or environmental modifications. This form of neuroplasticity is important at all stages of life but is critical in neurological disorders such as amblyopia and stroke. This review focuses upon our new understanding of possible mechanisms underlying functional deficits evidenced after adult-onset stroke. We review the functional interactions between different brain regions that may contribute to motor disability after stroke and, based on this information, possible interventional approaches to motor stroke disability. New information now points to the involvement of non-primary motor areas and their interaction with the primary motor cortex as areas of interest. The emergence of this new information is likely to impact new efforts to develop more effective neurorehabilitative interventions using transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) that may be relevant to other neurological disorders such as amblyopia.     

Disturbance of motor imagery after cerebellar stroke

The authors studied the possible involvement of the cerebellum in nonexecutive motor functions needed for a normal performance of complex motor patterns by analyzing (using chronometric evaluation) finger movement sequences and their respective motor imagery (a mental simulation of motor patterns). Patients suffering from a cerebellar stroke (n=11) were compared with aged-matched control volunteers (n=11). Patients that had apparently recovered from a unilateral cerebellar stroke showed a marked slowing of motor performance in both hands (ipsi- and contralateral to lesion). This effect was accompanied by a similar slowing of motor imagery, suggesting that the cerebellum, traditionally implicated in the control of motor execution, is also involved in nonexecutive motor functions such as the planning and internal simulation of movements.     

基于脑卒中后运动康复领域的运动想象的研究

脑卒中后造成的神经性损伤是目前导致患者运动功能性障碍的主要原因之一,为社会和患者家庭造成巨大的精神和经济负担。运动想象易学习、成本低,是辅助脑卒中后患者康复的重要手段之一,对改善患者运动功能障碍、提高生活质量具有重要意义。本文主要总结运动想象对脑卒中后康复的积极作用,概述运动想象的生理表现和理论模式、运动想象能力的影响因素、运动想象能力的评分标准,并分析目前运动想象在辅助脑卒中后患者运动功能的康复治疗过程中存在的实验对象单一、评估方法主观化、实验设备分辨率低等缺陷,希望帮助脑卒中后患者更加科学、有效地使用运动想象疗法。     

Sleep to learn after stroke: Implicit and explicit off-line motor learning

After stroke, many individuals experience persistent motor impairments as well as altered patterns of sleep. Therefore, examining the role of sleep in motor skill learning following stroke is a critical issue. Other learning variables, such as type of instruction, may interact with sleep to influence sleep-dependent motor learning. Forty individuals with stroke and 40 control participants practiced a continuous motor tracking task and then either slept (sleep condition) or stayed awake (no-sleep condition) between practice and retention testing. Half were provided explicit information regarding the presence of a repeating sequence (explicit condition), while the other half were not (implicit condition). After stroke, individuals demonstrated sleep-dependent off-line motor learning of both the implicit and explicit version of the continuous tracking task; however, individuals with stroke who stayed awake between practice and retention testing did not demonstrate an improvement in motor performance at retention. Neither sleep nor instruction differentiated the performance of the healthy control participants. These data suggest that aspects of motor recovery after stroke may be modulated by sleep.     

Implications of preserved written language abilities for the functional basis of speech automatisms (recurring utterances): A single case study

A patient is described whose oral speech consists exclusively of repetitively used stereotypical utterances (speech automatisms) but whose written performance is far better preserved. Written language investigation revealed that his phonological route for writing was not totally blocked. In writing to dictation, word length and syllabic structure were largely respected, even for nonwords. Picture-matching tasks which manipulated phonological similarity demonstrated relatively preserved access to lexical phonology. A nonlexical and sub-phonemic hypothesis of automatism-generation is proposed.     

Object motor representation and language

Results of kinematic studies on the control of the reaching–grasping motor act (Gentilucci 2003, Exp Brain Res 149:395–400) suggest that grasp is guided by a single motor representation, which codes all the possible types of interactions with the objects. Neuroimaging studies in humans (Chao and Martin 2000, Neuroimage 12:478–484; Grabowski et al. 1998, Neuroimage 7:232–243; Grafton et al. 1997, Neuroimage 6:231–236; Martin et al. 1995, Science 270:102–105) suggest that these representations are coded in the premotor cortex and are automatically activated when naming the object or viewing it without the execution of an overt action. If an object motor representation is accessed by language, naming of object properties related to sensory-motor transformation can automatically influence the object motor representation. This hypothesis was verified by behavioural experiments (Gentilucci and Gangitano 1998, Eur J Neurosci 10:752–756; Gentilucci et al. 2000, Exp Brain Res 133:468–490; Glover and Dixon 2002, Exp Brain Res 146:383–387), which showed that automatic reading (and probably silent naming; MacLeod 1991, Psychol Bull 109:163–203) of adjectives related to object properties analysed for planning the reaching–grasping motor act influenced the control of the arm movement. In a new study it was determined whether the class of a word can be a factor selectively influencing motor control. Participants were required to reach for and grasp an object located either on the right or on the left, and to place it on the opposite side. Either a verb ("place" SPOSTA versus "lift" ALZA) or an adjective ("lateral" LATERALE versus "high" ALTO) was printed on the target. A greater influence of the verbs than of the adjectives was observed on the kinematics of the action. In particular, when the verb ALZA was printed on the object, hand-path height and vertical component of arm velocity were higher than when the adjective ALTO was presented on the object. The data support the hypothesis that the object motor representation is mainly coded in terms of possible interactions with the object.     

Somatotopic mapping of the human primary sensorimotor cortex during motor imagery and motor execution by functional magnetic resonance imaging

Autosomal recessive parkinsonism associated with mutations in the parkin gene represents a monogenic form of hereditary parkinsonism. We performed [(18)F]6-fluorodopa (FDOPA) positron emission tomography as a measurement of the nigrostriatal dopaminergic system as well as extensive haplotype analysis of the PARK 2 gene locus in 14 subjects with parkin mutations. In parkin subjects, the reduction of striatal FDOPA uptake increased with the number of mutated alleles and was also slightly obvious in asymptomatic parkin gene carriers in the heterozygous state. The abnormal FDOPA uptake pattern in parkin patients did not significantly differ from that of sporadic Parkinson's disease. Our data are in agreement with an enzymatic dysfunction of the gene's translational product, which has been shown to promote protein degradation as an ubiquitin-protein ligase. Thus, parkinsonism in parkin gene carriers may be related to abnormal nigral protein accumulation in the presence of a suprathreshold enzyme dysfunction.     

Ipsilateral responses of motor evoked potential correlated with the motor functional outcomes after cortical resection

The aim of this study was to evaluate if ipsilateral motor evoked potential (MEP) elicited by transcranial magnetic stimulation (TMS) could provide neurosurgeons preoperatively with useful information regarding surgical procedure for patients with severe cerebral hemiatrophy or unilateral malformation. Thirteen epilepsy patients with severe cerebral hemiatrophy or unilateral malformation were studied before operation using MEPs recorded on bilateral abductor pollicis brevis (APBs) muscles, elicited by transcranial magnetic stimulation of the motor cortex. Ten subjects served as controls. Results: (1) no ipsilateral MEP responses were recorded in all the 10 healthy subjects; (2) in the 13 patients, the results of MEPs could be divided into four types. Type A: in 3 patients bilateral MEPs were recorded when unaffected hemisphere was stimulated, while no responses were elicited when the affected hemisphere was stimulated. Type B: in another 3 patients, the MEPs were elicited from bilateral APB muscles when the unaffected hemisphere was stimulated, and the contralateral MEP was also elicited when the affected hemisphere was stimulated. Type C: in two patients contralateral MEP was elicited when the unaffected hemisphere was stimulated, while no MEP was induced in APB muscles of either side following the affected hemisphere stimulation. Type D: in the remaining 5 patients, contralateral magnetic MEPs were elicited either when the affected or the unaffected hemisphere was stimulated. Patients of type A, B and C received hemispherectomy showed no significant permanent motor functional deficit. Among the total 8 patients, 7 patients got seizure free after the operation. Patients of type D showed minor muscle strength decrease after localized cortical resection. Three out of 5 patients of type D got seizure free after the operation. Ipsilateral MEP response might be useful for neurosurgeons to plan appropriate surgical procedure which helps avoid post-operative motor deficits.     

The left parietal cortex and motor intention: an event-related functional magnetic resonance imaging study

Traditionally the posterior parietal cortex was believed to be a sensory structure. More recently, however, its important role in sensory-motor integration has been recognized. One of its functions suggested in this context is the forming of intentions, i.e. high-level cognitive plans for movements. The selection and planning of a specific movement defines motor intention. In this study we used rapid event-related functional magnetic resonance imaging of healthy human subjects to investigate the involvement of posterior parietal cortex in motor intention in response to valid imperative cues. Subjects were provided with either neutral, motor or spatial cues. Neutral cues simply alerted, motor cues indicated which hand to use for response, and spatial cues indicated on which side the target would appear. Importantly, identical targets and responses followed these cues. Therefore any differential neural effects observed are independent from the actual movement performed. Differential blood oxygen level dependent signal changes for motor vs. neutral as well as motor vs. spatial cue trials were found in the left supramarginal gyrus, as hypothesized. The results demonstrate that neural activity in the left supramarginal gyrus underlies motor plans independent from the execution of the movement and thus extend previous neuropsychological and functional imaging data on the role of the left supramarginal gyrus in higher motor cognition.     

Recovery of motor functions after division of the spinal cord or cauda equina

Partial recovery of motor functions in 8 patients with division of the spinal cord at the mid-thoracic level or of the cauda equina at the lumbar level is described. During attempts by all patients at voluntary movement, electromyography revealed the development of activity in the trunk muscles and m. gluteus medius, as well as the appearance and development of activity in muscles of the thigh and leg. The level of rehabilitation in the patients was relatively high: They could walk with suitable support, they could work at their own trades, and they could care for themselves. Recovery of motor functions took place more rapidly after trauma at lower levels, although complete rehabilitation was achieved in two patients with trauma at a higher level. The mechanism of restoration of functions is based on the compensatory development of activity in the trunk muscles and the ability of the distal segment of the spinal cord to form new motor reflexes with the participation of the limb muscles.Institute for Problems in Information Transmission, Academy of Sciences of the USSR. No. 18 Mecical Physical Culture Dispensary, Moscow. (Presented by Academician of Academy of Medical Sciences of the USSR V. S. Rusinov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 88, No. 7, pp. 15–18, July, 1979.     

Myobiofeedback in motor reeducation of wrist and fingers after hemispherial stroke.

32 patients with different grade of hemiparesis, were in the first weeks after a cerebral vascular accident treated by means of EMG-feedback in respect to volar and dorsal flexion of the wrist, flexion and extension of the fingers, and opposition of thumb to the second ev. other fingers. EMG was registered from suitable muscles of the paretic limb. The attempt of volitional movement at the paretic side was conditioned with a reinforced mirror synergia of the same type from the healthy to the damaged side. The patient observed the effect on the EMG screen. After 3-6 conditionings the patient performed the volitional movement alone. In 25 of patients (e.g. 78.1%) improvement was obtained, at least in EMG. A good correlation was found between effect of the procedures and severity of paresis (p less than 0.05; chi 2 = 7.35).     

Renewal of the neurophysiology of language: functional neuroimaging

Functional neuroimaging methods have reached maturity. It is now possible to start to build the foundations of a physiology of language. The remarkable number of neuroimaging studies performed so far illustrates the potential of this approach, which complements the classical knowledge accumulated on aphasia. Here we attempt to characterize the impact of the functional neuroimaging revolution on our understanding of language. Although today considered as neuroimaging techniques, we refer less to electroencephalography and magnetoencephalography studies than to positron emission tomography and functional magnetic resonance imaging studies, which deal more directly with the question of localization and functional neuroanatomy. This review is structured in three parts. 1) Because of their rapid evolution, we address technical and methodological issues to provide an overview of current procedures and sketch out future perspectives. 2) We review a set of significant results acquired in normal adults (the core of functional imaging studies) to provide an overview of language mechanisms in the "standard" brain. Single-word processing is considered in relation to input modalities (visual and auditory input), output modalities (speech and written output), and the involvement of "central" semantic processes before sentence processing and nonstandard language (illiteracy, multilingualism, and sensory deficits) are addressed. 3) We address the influence of plasticity on physiological functions in relation to its main contexts of appearance, i.e., development and brain lesions, to show how functional imaging can allow fine-grained approaches to adaptation, the fundamental property of the brain. In closing, we consider future developments for language research using functional imaging.     

The contribution(s) of the insula to speech production: a review of the clinical and functional imaging literature

Skilled spoken language production requires fast and accurate coordination of up to 100 muscles. A long-standing concept—tracing ultimately back to Paul Broca—assumes posterior parts of the inferior frontal gyrus to support the orchestration of the respective movement sequences prior to innervation of the vocal tract. At variance with this tradition, the insula has more recently been declared the relevant “region for coordinating speech articulation”, based upon clinico-neuroradiological correlation studies. However, these findings have been criticized on methodological grounds. A survey of the clinical literature (cerebrovascular disorders, brain tumours, stimulation mapping) yields a still inconclusive picture. By contrast, functional imaging studies report more consistently hemodynamic insular responses in association with motor aspects of spoken language. Most noteworthy, a relatively small area at the junction of insular and opercular cortex was found sensitive to the phonetic-linguistic structure of verbal utterances, a strong argument for its engagement in articulatory control processes. Nevertheless, intrasylvian hemodynamic activation does not appear restricted to articulatory processes and might also be engaged in the adjustment of the autonomic system to ventilatory needs during speech production: Whereas the posterior insula could be involved in the cortical representation of respiration-related metabolic (interoceptive) states, the more rostral components, acting upon autonomic functions, might serve as a corollary pathway to “voluntary control of breathing” bound to corticospinal and -bulbar fiber tracts. For example, the insula could participate in the implementation of task-specific autonomic settings such as the maintenance of a state of relative hyperventilation during speech production.     

Speed of motor re-learning after experimental stroke depends on prior skill

Many motor rehabilitation therapies are based on principles of motor learning. Motor learning depends on preliminary knowledge of the trained and other (similar) skills. This study sought to investigate the influence of prior skill knowledge on re-learning of a precision reaching skill after a cortical lesion in rat. One group of animals recovered a previously known skill (skill training, followed by stroke and re-learning training, TST, n = 8). A second group learned the skill for the first time after stroke (ST, n = 6). A control group received prolonged training without stroke (n = 6). Unilateral partial motor cortex lesions were induced photothrombotically after identifying the forelimb representation using epidural stimulation mapping. In TST animals, re-learning after stroke was slower than learning before stroke (post hoc repeated measures ANOVA P = 0.039) and learning in the control group (P = 0.033). De novo learning after stroke (ST group) was not different from healthy learning. These findings show that skill learning can be performed if the motor cortex is partially lesioned; re-learning of a skill after stroke is slowed by prior knowledge of the skill. It remains to be tested in humans whether task novelty positively influences rehabilitation therapy.     

On-line 'automatic pilot' training for hand and arm motor rehabilitation after stroke

As stroke being one of the most leading causes of death worldwide, even stroke survivors have to suffer from dysfunctions of limb controls and inabilities of speech or vision. Cognitive neuroscientists have found various forms of automatic behaviours in healthy people, which generally cover motor components of upper limbs and are essential for coordination and mobility relevant activities. Meanwhile, the robot-assisted therapy and functional electrical stimulation have become prominent rehabilitation techniques for patients' rehabilitation after stroke. With the integration of robot-aided therapeutic systems and the functional electrical stimulation, the on-line 'automatic pilot' training of the visual inspired stimulation for upper limbs can offer a feasible treatment for patients after stroke to recover motor performance.     

Early treadmill training promotes motor function after hemorrhagic stroke in rats

Rehabilitation after a stroke is very important because it has beneficial effects on brain function, including the promotion of plasticity. However, an optimal time window for rehabilitation interventions after hemorrhagic stroke has not been clearly defined. The aim of this study was to determine whether early exercise training initiated 24 h after an intracerebral hemorrhage (ICH) might enhance neurologic recovery more than exercise initiated 1 week after ICH without hematoma expansion and edema volume increase. We subjected adult male Sprague–Dawley rats to experimental ICH by the intrastriatal administration of bacterial collagenase. The rats were randomly divided into the following 2 groups: early training group (treadmill exercise started 24 h post-ICH; n = 18) and late training group (treadmill exercise started 1-week post-ICH; n = 18). Two weeks after surgery we performed neurologic tests (rota-rod, modified limb-placing, and adhesive-dot removal tests), and measured hematoma volumes and brain water content. In the late training group, compared with the pre-ICH performance on the rota-rod test (98.3 ± 69.4 s), the animals had significantly worse performance after the post-ICH rehabilitation (40.5 ± 52.6 s; p < 0.01, paired t-test). In the early training group however, the motor performance after the post-ICH rehabilitation (56.4 ± 73.5 s) was not significantly different from the baseline pre-ICH performance (79.8 ± 33.9 s; p = 0.24). There were no significant differences between the two groups with respect to the other neurologic tests. Early exercise did not increase hematoma size or brain water content. Early treadmill training could be performed safely, and enhanced motor recovery in a rat model of ICH. Further studies are required to translate the results into clinical significance.     

Axon sprouting in adult mouse spinal cord after motor cortex stroke

Functional reorganization of brain cortical areas occurs following stroke in humans, and many instances of this plasticity are associated with recovery of function. Rodent studies have shown that following a cortical stroke, neurons in uninjured areas of the brain are capable of sprouting new axons into areas previously innervated by injured cortex. The pattern and extent of structural plasticity depend on the species, experimental model, and lesion localization. In this study, we examined the pattern of axon sprouting in spinal cord after a localized lesion which selectively targeted the primary motor cortex in adult mice. We subjected mice to a stereotaxic-guided photothrombotic stroke of the left motor cortex, followed 2 weeks later by an injection of the neuronal tracer biotinylated dextran amine (BDA) into the uninjured right motor cortex. BDA-positive axons originating from the uninjured motor cortex were increased in the gray matter of the right cervical spinal cord in stroke mice, compared to sham control mice. These results show that axon sprouting can occur in the spinal cord of adult wild-type mice after a localized stroke in motor cortex.