Intact motor imagery in chronic upper limb hemiplegics: evidence for activity-independent action representations

The therapeutic role of motor imagery on the functional rehabilitation of a stage II shoulder impingement syndrome

PURPOSE

Motor imagery (MI) has been used as a complementary therapeutic tool for motor recovery after central nervous system disease and peripheral injuries. However, it has never been used as a preventive tool. We investigated the use of MI in the rehabilitation of stage II shoulder impingement syndrome. For the first time, MI is used before surgery.

METHOD

Sixteen participants were randomly assigned to either a MI or control group. Shoulder functional assessment (Constant score), range of motion and pain were measured before and after intervention.

RESULTS

Higher Constant score was observed in the MI than in the control group (p=0.04). Participants in the MI group further displayed greater movement amplitude (extension (p<0.001); flexion (p=0.025); lateral rotation (p<0.001). Finally, the MI group showed greater pain decrease (p=0.01).

CONCLUSION

MI intervention seems to alleviate pain and enhance mobility, this is probably due to changes in muscle control and consequently in joint amplitude. MI might contribute to postpone or even protect from passing to stage III that may require surgery. Implications for Rehabilitation Adding motor imagery training to classical physical therapy in a stage II impingement syndrome: Helps in alleviating pain Enhances shoulder mobility Motor imagery is a valuable technique that can be used as a preventive tool before the stage III of the impingement syndrome.

Age-specific activation of cerebral areas in motor imagery--a fMRI study

INTRODUCTION

The objectives of this study were to study the age-specific activation patterns of cerebral areas during motor execution (ME) and motor imaging (MI) of the upper extremities and to discuss the age-related neural mechanisms associated with ME or MI.

METHODS

The functional magnetic resonance imaging technique was used to monitor the pattern and intensity of brain activation during the ME and MI of the upper extremities in 20 elderly (>50 years) and 19 young healthy subjects (<25 years).

RESULTS

No major differences were identified regarding the activated brain areas during ME or MI between the two groups; however, a minor difference was noted. The intensity of the activated brain area during ME was stronger in the older group than in the younger group, while the results with MI were the opposite. The posterior central gyrus and supplementary motor area during MI were more active in the younger group than in the older group. The putamen, lingual, and so on demonstrated stronger activation during dominant hand MI in the older group.

CONCLUSION

The results of this study revealed that the brain structure was altered and that neuronal activity was attenuated with age, and the cerebral cortex and subcortical tissues were found to be over-activated to achieve the same level of ME and MI, indicating that the activating effects of the left hemisphere enhanced with age, whereas the inhibitory effects declined during ME, and activation of the right hemisphere became more difficult during MI.

Is motor-imagery brain-computer interface feasible in stroke rehabilitation?

In the past 3 decades, interest has increased in brain-computer interface (BCI) technology as a tool for assisting, augmenting, and rehabilitating sensorimotor functions in clinical populations. Initially designed as an assistive device for partial or total body impairments, BCI systems have since been explored as a possible adjuvant therapy in the rehabilitation of patients who have had a stroke. In particular, BCI systems incorporating a robotic manipulanda to passively manipulate affected limbs have been studied. These systems can use a range of invasive (ie, intracranial implanted electrodes) or noninvasive neurophysiologic recording techniques (ie, electroencephalography [EEG], near-infrared spectroscopy, and magnetoencephalography) to establish communication links between the brain and the BCI system. Trials are most commonly performed on EEG-based BCI in comparison with the other techniques because of its high temporal resolution, relatively low setup costs, portability, and noninvasive nature. EEG-based BCI detects event-related desynchronization/synchronization in sensorimotor oscillatory rhythms associated with motor imagery (MI), which in turn drives the BCI. Previous evidence suggests that the process of MI preferentially activates sensorimotor regions similar to actual task performance and that repeated practice of MI can induce plasticity changes in the brain. It is therefore postulated that the combination of MI and BCI may augment rehabilitation gains in patients who have had a stroke by activating corticomotor networks via MI and providing sensory feedback from the affected limb using end-effector robots. In this review we examine the current literature surrounding the feasibility of EEG-based MI-BCI systems in stroke rehabilitation. We also discuss the limitations of using EEG-based MI-BCI in patients who have had a stroke and suggest possible solutions to overcome these limitations.

Neurophysiological correlates of visuo-motor learning through mental and physical practice

We have previously shown that mental rehearsal can replace up to 75% of physical practice for learning a visuomotor task (Allami, Paulignan, Brovelli, & Boussaoud, (2008). Experimental Brain Research, 184, 105-113). Presumably, mental rehearsal must induce brain changes that facilitate motor learning. We tested this hypothesis by recording scalp electroencephalographic activity (EEG) in two groups of subjects. In one group, subjects executed a reach to grasp task for 240 trials. In the second group, subjects learned the task through a combination of mental rehearsal for the initial 180 trials followed by the execution of 60 trials. Thus, one group physically executed the task for 240 trials, the other only for 60 trials. Amplitudes and latencies of event-related potentials (ERPs) were compared across groups at different stages during learning. We found that ERP activity increases dramatically with training and reaches the same amplitude over the premotor regions in the two groups, despite large differences in physically executed trials. These findings suggest that during mental rehearsal, neuronal changes occur in the motor networks that make physical practice after mental rehearsal more effective in configuring functional networks for skilful behaviour.

Neurophysiological substrates of stroke patients with motor imagery-based Brain-Computer Interface training

We investigated the efficacy of motor imagery-based Brain Computer Interface (MI-based BCI) training for eight stroke patients with severe upper extremity paralysis using longitudinal clinical assessments. The results were compared with those of a control group (n = 7) that only received FES (Functional Electrical Stimulation) treatment besides conventional therapies. During rehabilitation training, changes in the motor function of the upper extremity and in the neurophysiologic electroencephalographic (EEG) were observed for two groups. After 8 weeks of training, a significant improvement in the motor function of the upper extremity for the BCI group was confirmed (p < 0.05 for ARAT), simultaneously with the activation of bilateral cerebral hemispheres. Additionally, event-related desynchronization (ERD) of the affected sensorimotor cortexes (SMCs) was significantly enhanced when compared to the pretraining course, which was only observed in the BCI group (p < 0.05). Furthermore, the activation of affected SMC and parietal lobe were determined to contribute to motor function recovery (p < 0.05). In brief, our findings demonstrate that MI-based BCI training can enhance the motor function of the upper extremity for stroke patients by inducing the optimal cerebral motor functional reorganization.

Meta-analysis on the effect of mental imagery on motor recovery of the hemiplegic upper extremity function

BACKGROUND/AIM

Studies have shown that mental imagery can enhance relearning and generalisation of function after stroke. The aim of this meta-analysis was to evaluate evidence on the effects of mental imagery on motor recovery of the hemiplegic upper extremities after stroke.

METHODS

A comprehensive data base search of the literature up to December 2012 was performed using PubMed, EBSCO host (Academic Search Premier, CINAHL and Educational Resource Information Center), PsycINFO, Medline, and ISI Web of Knowledge (Science Citation Index and Social Sciences Citation Index). Randomised clinical trials or controlled clinical trials that included mental imagery for improving upper extremity motor function for stroke patients were located. Relevant articles were critically reviewed and methodological quality was evaluated using the PEDro Scale, and study results synthesised.

RESULTS

Five randomised clinical trials and one controlled clinical trial met the inclusion criteria. Five of the six studies yielded positive findings in favour of mental imagery. Quantitative analysis showed a significant difference in the Action Research Arm Test (overall effect: Z=6.75; P<<0.001).

CONCLUSION

Review of the literature revealed a trend in support of the use of motor imagery for upper extremity motor rehabilitation after stroke. Mental imagery could be a viable intervention for stroke patients given its benefits of being safe, cost-effective and rendering multiple and unlimited practice opportunities. It is recommended that researchers incorporate imaging techniques into clinical studies so that the mechanism whereby mental imagery mediates motor recovery or neural adaptation for people with stroke can be better understood.

Brain-machine interface in chronic stroke rehabilitation: a controlled study

OBJECTIVE

Chronic stroke patients with severe hand weakness respond poorly to rehabilitation efforts. Here, we evaluated efficacy of daily brain-machine interface (BMI) training to increase the hypothesized beneficial effects of physiotherapy alone in patients with severe paresis in a double-blind sham-controlled design proof of concept study.

METHODS

Thirty-two chronic stroke patients with severe hand weakness were randomly assigned to 2 matched groups and participated in 17.8 ± 1.4 days of training rewarding desynchronization of ipsilesional oscillatory sensorimotor rhythms with contingent online movements of hand and arm orthoses (experimental group, n = 16). In the control group (sham group, n = 16), movements of the orthoses occurred randomly. Both groups received identical behavioral physiotherapy immediately following BMI training or the control intervention. Upper limb motor function scores, electromyography from arm and hand muscles, placebo-expectancy effects, and functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent activity were assessed before and after intervention.

RESULTS

A significant group × time interaction in upper limb (combined hand and modified arm) Fugl-Meyer assessment (cFMA) motor scores was found. cFMA scores improved more in the experimental than in the control group, presenting a significant improvement of cFMA scores (3.41 ± 0.563-point difference, p = 0.018) reflecting a clinically meaningful change from no activity to some in paretic muscles. cFMA improvements in the experimental group correlated with changes in fMRI laterality index and with paretic hand electromyography activity. Placebo-expectancy scores were comparable for both groups.

INTERPRETATION

The addition of BMI training to behaviorally oriented physiotherapy can be used to induce functional improvements in motor function in chronic stroke patients without residual finger movements and may open a new door in stroke neurorehabilitation.

Transcranial direct current stimulation and EEG-based motor imagery BCI for upper limb stroke rehabilitation

Clinical studies had shown that EEG-based motor imagery Brain-Computer Interface (MI-BCI) combined with robotic feedback is effective in upper limb stroke rehabilitation, and transcranial Direct Current Stimulation (tDCS) combined with other rehabilitation techniques further enhanced the facilitating effect of tDCS. This motivated the current clinical study to investigate the effects of combining tDCS with MI-BCI and robotic feedback compared to sham-tDCS for upper limb stroke rehabilitation. The stroke patients recruited were randomized to receive 20 minutes of tDCS or sham-tDCS prior to 10 sessions of 1-hour MI-BCI with robotic feedback for 2 weeks. The online accuracies of detecting motor imagery from idle condition were assessed and offline accuracies of classifying motor imagery from background rest condition were assessed from the EEG of the evaluation and therapy parts of the 10 rehabilitation sessions respectively. The results showed no evident differences between the online accuracies on the evaluation part from both groups, but the offline analysis on the therapy part yielded higher averaged accuracies for subjects who received tDCS (n=3) compared to sham-tDCS (n=2). The results suggest towards tDCS effect in modulating motor imagery in stroke, but a more conclusive result can be drawn when more data are collected in the ongoing study.

Imagined actions in multiple sclerosis patients: evidence of decline in motor cognitive prediction

Motor imagery is a mental process during which subjects internally simulate a movement without any motor output. Mental and actual movement durations are similar in healthy adults (isochrony) while temporal discrepancies (anisochrony) could be an expression of neurological deficits on action representation. It is unclear whether patients with multiple sclerosis (PwMS) preserve the capacity to simulate their own movements. This study investigates the ability of PwMS to predict their own actions by comparing temporal features of dominant and non-dominant actual and mental actions. Fourteen PwMS and nineteen healthy subjects (HS) were asked to execute and to imagine pointing arm movements among four pairs of targets of different sizes. Task duration was calculated for both actual and mental movements by an optoelectronic device. Results showed temporal consistency and target-by-target size modulation in actual movements through the four cycles for both groups with significantly longer actual and mental movement durations in PwMS with respect to HS. An index of performance (IP) was used to examine actual/mental isochrony properties in the two groups. Statistical analysis on IP showed in PwMS significantly longer actual movement durations with respect to mental movement durations (anisochrony), more relevant for the non-dominant than dominant arm. Mental prediction of motor actions is not well preserved in MS where motor and cognitive functional changes are present. Differences in performing imagined task with dominant and non-dominant arm could be related to increased cognitive effort required for performing non-dominant movements.

Neural correlates of motor impairment during motor imagery and motor execution in sub-cortical stroke

OBJECTIVE

This study aims at identifying the neural substrates for motor execution (ME) and motor imagery (MI) in patients after stroke and their correlations with functional outcomes.

METHODS

10 chronic stroke patients with left sub-cortical lesions and 10 unimpaired subjects were recruited. Their cortical processes were studied when they were asked to perform ME and MI unimanually using their unaffected and affected wrists during fMRI.

RESULTS

From correlation results, the supplementary motor area (SMA), its activation volume and congruence in functional neuroanatomy associated with ME and MI using affected wrist positively correlated with motor performance. During ME of the affected wrist, the precuneus, its activation volume and congruence in functional neuroanatomy between patient and unimpaired groups showed a negative correlation, while, in non-primary motor areas, the hemispheric balance of premotor cortex and the congruence in functional neuroanatomy of contralesional inferior parietal lobule between patient and unimpaired groups showed a positive correlation with motor performance.

CONCLUSIONS

The non-primary motor-related areas were revealed to play a critical role in determining motor outcomes after left sub-cortical stroke, which was demonstrated in the stroke patients. In particular, SMA might be the key neural substrate associated with motor recovery.

Brain Activation in Primary Motor and Somatosensory Cortices during Motor Imagery Correlates with Motor Imagery Ability in Stroke Patients

Aims. While studies on healthy subjects have shown a partial overlap between the motor execution and motor imagery neural circuits, few have investigated brain activity during motor imagery in stroke patients with hemiparesis. This work is aimed at examining similarities between motor imagery and execution in a group of stroke patients. Materials and Methods. Eleven patients were asked to perform a visuomotor tracking task by either physically or mentally tracking a sine wave force target using their thumb and index finger during fMRI scanning. MIQ-RS questionnaire has been administered. Results and Conclusion. Whole-brain analyses confirmed shared neural substrates between motor imagery and motor execution in bilateral premotor cortex, SMA, and in the contralesional inferior parietal lobule. Additional region of interest-based analyses revealed a negative correlation between kinaesthetic imagery ability and percentage BOLD change in areas 4p and 3a; higher imagery ability was associated with negative and lower percentage BOLD change in primary sensorimotor areas during motor imagery.

Physical experience leads to enhanced object perception in parietal cortex: insights from knot tying

What does it mean to "know" what an object is? Viewing objects from different categories (e.g., tools vs. animals) engages distinct brain regions, but it is unclear whether these differences reflect object categories themselves or the tendency to interact differently with objects from different categories (grasping tools, not animals). Here we test how the brain constructs representations of objects that one learns to name or physically manipulate. Participants learned to name or tie different knots and brain activity was measured whilst performing a perceptual discrimination task with these knots before and after training. Activation in anterior intraparietal sulcus, a region involved in object manipulation, was specifically engaged when participants viewed knots they learned to tie. This suggests that object knowledge is linked to sensorimotor experience and its associated neural systems for object manipulation. Findings are consistent with a theory of embodiment in which there can be clear overlap in brain systems that support conceptual knowledge and control of object manipulation.

Imagining is Not Doing but Involves Specific Motor Commands: A Review of Experimental Data Related to Motor Inhibition

There is now compelling evidence that motor imagery (MI) and actual movement share common neural substrate. However, the question of how MI inhibits the transmission of motor commands into the efferent pathways in order to prevent any movement is largely unresolved. Similarly, little is known about the nature of the electromyographic activity that is apparent during MI. In addressing these gaps in the literature, the present paper argues that MI includes motor execution commands for muscle contractions which are blocked at some level of the motor system by inhibitory mechanisms. We first assemble data from neuroimaging studies that demonstrate that the neural networks mediating MI and motor performance are not totally overlapping, thereby highlighting potential differences between MI and actual motor execution. We then review MI data indicating the presence of subliminal muscular activity reflecting the intrinsic characteristics of the motor command as well as increased corticomotor excitability. The third section not only considers the inhibitory mechanisms involved during MI but also examines how the brain resolves the problem of issuing the motor command for action while supervising motor inhibition when people engage in voluntary movement during MI. The last part of the paper draws on imagery research in clinical contexts to suggest that some patients move while imagining an action, although they are not aware of such movements. In particular, experimental data from amputees as well as from patients with Parkinson’s disease are discussed. We also review recent studies based on comparing brain activity in tetraplegic patients with that from healthy matched controls that provide insights into inhibitory processes during MI. We conclude by arguing that based on available evidence, a multifactorial explanation of motor inhibition during MI is warranted.

Cognitive alterations in motor imagery process after left hemispheric ischemic stroke

BACKGROUND

Motor imagery training is a promising rehabilitation strategy for stroke patients. However, few studies had focused on the neural mechanisms in time course of its cognitive process. This study investigated the cognitive alterations after left hemispheric ischemic stroke during motor imagery task.

METHODOLOGY/PRINCIPAL FINDINGS

Eleven patients with ischemic stroke in left hemisphere and eleven age-matched control subjects participated in mental rotation task (MRT) of hand pictures. Behavior performance, event-related potential (ERP) and event-related (de)synchronization (ERD/ERS) in beta band were analyzed to investigate the cortical activation. We found that: (1) The response time increased with orientation angles in both groups, called "angle effect", however, stoke patients' responses were impaired with significantly longer response time and lower accuracy rate; (2) In early visual perceptual cognitive process, stroke patients showed hypo-activations in frontal and central brain areas in aspects of both P200 and ERD; (3) During mental rotation process, P300 amplitude in control subjects decreased while angle increased, called "amplitude modulation effect", which was not observed in stroke patients. Spatially, patients showed significant lateralization of P300 with activation only in contralesional (right) parietal cortex while control subjects showed P300 in both parietal lobes. Stroke patients also showed an overall cortical hypo-activation of ERD during this sub-stage; (4) In the response sub-stage, control subjects showed higher ERD values with more activated cortical areas particularly in the right hemisphere while angle increased, named "angle effect", which was not observed in stroke patients. In addition, stroke patients showed significant lower ERD for affected hand (right) response than that for unaffected hand.

CONCLUSIONS/SIGNIFICANCE

Cortical activation was altered differently in each cognitive sub-stage of motor imagery after left hemispheric ischemic stroke. These results will help to understand the underlying neural mechanisms of mental rotation following stroke and may shed light on rehabilitation based on motor imagery training.

Comparative investigations of manual action representations: evidence that chimpanzees represent the costs of potential future actions involving tools

The ability to adjust one's ongoing actions in the anticipation of forthcoming task demands is considered as strong evidence for the existence of internal action representations. Studies of action selection in tool use reveal that the behaviours that we choose in the present moment differ depending on what we intend to do next. Further, they point to a specialized role for mechanisms within the human cerebellum and dominant left cerebral hemisphere in representing the likely sensory costs of intended future actions. Recently, the question of whether similar mechanisms exist in other primates has received growing, but still limited, attention. Here, we present data that bear on this issue from a species that is a natural user of tools, our nearest living relative, the chimpanzee. In experiment 1, a subset of chimpanzees showed a non-significant tendency for their grip preferences to be affected by anticipation of the demands associated with bringing a tool's baited end to their mouths. In experiment 2, chimpanzees' initial grip preferences were consistently affected by anticipation of the forthcoming movements in a task that involves using a tool to extract a food reward. The partial discrepancy between the results of these two studies is attributed to the ability to accurately represent differences between the motor costs associated with executing the two response alternatives available within each task. These findings suggest that chimpanzees are capable of accurately representing the costs of intended future actions, and using those predictions to select movements in the present even in the context of externally directed tool use.

Neurofeedback using real-time near-infrared spectroscopy enhances motor imagery related cortical activation

Accumulating evidence indicates that motor imagery and motor execution share common neural networks. Accordingly, mental practices in the form of motor imagery have been implemented in rehabilitation regimes of stroke patients with favorable results. Because direct monitoring of motor imagery is difficult, feedback of cortical activities related to motor imagery (neurofeedback) could help to enhance efficacy of mental practice with motor imagery. To determine the feasibility and efficacy of a real-time neurofeedback system mediated by near-infrared spectroscopy (NIRS), two separate experiments were performed. Experiment 1 was used in five subjects to evaluate whether real-time cortical oxygenated hemoglobin signal feedback during a motor execution task correlated with reference hemoglobin signals computed off-line. Results demonstrated that the NIRS-mediated neurofeedback system reliably detected oxygenated hemoglobin signal changes in real-time. In Experiment 2, 21 subjects performed motor imagery of finger movements with feedback from relevant cortical signals and irrelevant sham signals. Real neurofeedback induced significantly greater activation of the contralateral premotor cortex and greater self-assessment scores for kinesthetic motor imagery compared with sham feedback. These findings suggested the feasibility and potential effectiveness of a NIRS-mediated real-time neurofeedback system on performance of kinesthetic motor imagery. However, these results warrant further clinical trials to determine whether this system could enhance the effects of mental practice in stroke patients.

Reduced upper limb sensation impairs mental chronometry for motor imagery after stroke: clinical and electrophysiological findings

BACKGROUND

Motor imagery (MI) is increasingly recognized as a treatment option after stroke, but not all stroke patients are able to perform MI.

OBJECTIVE

To examine if severe somatosensory deficits would affect MI ability.

METHODS

The Box and Block Test (BBT) was used to evaluate mental chronometry as 1 component of MI. Two groups of stroke patients and an age-matched healthy control group (CG) were studied. Patient group 1 (n = 10, PG1) had a severe somatosensory impairment on the affected side and PG2 (n = 10) had pure motor strokes. All subjects first performed the BBT in a mental and in a real version. The time needed to move 15 blocks from 1 side of the box to the other was measured. To compare the groups independently of their performance level, a (real performance--MI)/(real performance) ratio was calculated. Corticospinal excitability was measured by transcranial magnetic stimulation at rest and while the subjects performed an imagined pinch grip.

RESULTS

The CG performed the BBT faster than both patient groups, and PG1 was slower than PG2. MI ability was impaired in PG1 but only for the affected hand. Transcranial magnetic stimulation data showed an abnormally low MI-induced corticospinal excitability increase for the affected hand in PG1, but not in PG2.

CONCLUSIONS

Severe somatosensory deficits impaired mental chronometry. A controlled study is necessary to clarify if these patients benefit at all from MI as an additional treatment.

Brain simulation of action may be grounded in physical experience

An intriguing quality of our brain is that when actions are imagined, corresponding brain regions are recruited as when the actions are actually performed. It has been hypothesized that the similarity between real and simulated actions depends on the nature of motor representations. Here we tested this hypothesis by examining S.D., who never used her legs but is an elite wheel chair athlete. Controls recruited motor brain regions during imagery of stair walking and frontal regions during imagery of wheel chair slalom. S.D. showed the opposite pattern. Thus, brain simulation of actions may be grounded in specific physical experiences.

A large clinical study on the ability of stroke patients to use an EEG-based motor imagery brain-computer interface

Brain-computer interface (BCI) technology has the prospects of helping stroke survivors by enabling the interaction with their environ ment through brain signals rather than through muscles, and restoring motor function by inducing activity-dependent brain plasticity. This paper presents a clinical study on the extent of detectable brain signals from a large population of stroke patients in using EEG-based motor imagery BCI. EEG data were collected from 54 stroke patients whereby finger tapping and motor imagery of the stroke-affected hand were performed by 8 and 46 patients, respectively. EEG data from 11 patients who gave further consent to perform motor imagery were also collected for second calibration and third independent test sessions conducted on separate days. Off-line accuracies of classifying the two classes of EEG from finger tapping or motor imagery of the stroke-affected hand versus the EEG from background rest were then assessed and compared to 16 healthy subjects. The mean off-line accuracy of detecting motor imagery by the 46 patients (mu=0.74) was significantly lower than finger tapping by 8 patients (mu=0.87, p=0.008), but not significantly lower than motor imagery by healthy subjects (mu=0.78, p=0.23). Six stroke patients performed motor imagery at chance level, and no correlation was found between the accuracies of detecting motor imagery and their motor impairment in terms of Fugl-Meyer Assessment (p=0.29). The off-line accuracies of the 11 patients in the second session (mu=0.76) were not significantly different from the first session (mu=0.72, p=0.16), or from the on-line accuracies of the third independent test session (mu=0.82, p=0.14). Hence this study showed that the majority of stroke patients could use EEG-based motor imagery BCI.

Preserved grip selection planning in chronic unilateral upper extremity amputees

Upper limb amputees receive no proprioceptive or visual sensory feedback about their absent hand. In this study, we asked whether chronic amputees nevertheless retain the ability to accurately plan gripping movements. Fourteen patients and matched controls performed two grip selection tasks: overt grip selection (OGS), in which they used their intact hand to grasp an object that appeared in different orientations using the most natural (under- or overhand) precision grip, and prospective grip selection (PGS), in which they selected the most natural grip for either hand without moving. We evaluated planning accuracy by comparing concordance between grip preferences expressed in PGS vs. OGS for the intact hand and PGS vs. the inverse of OGS responses for the affected hand. Overall, amputees showed no deficits in the accuracy of grip selection planning based on either hand and a consistent preference for less awkward hand postures. We found no evidence for a speed-accuracy tradeoff. Furthermore, selection accuracy did not depend on phantom mobility, phantom limb pain, time since amputation, or the residual limb's shoulder posture. Our findings demonstrate that unilateral upper limb amputees retain the ability to plan movements based on the biomechanics of their affected hand even many years after limb loss. This unimpaired representation may stem from persistent higher-level activity-independent internal representations or may be sustained by sensory feedback from the intact hand.

Recovery of motor imagery ability in stroke patients

Objective. To investigate whether motor imagery ability recovers in stroke patients and to see what the relationship is between different types of imagery and motor functioning after stroke. Methods. 12 unilateral stroke patients were measured at 3 and 6 weeks poststroke on 3 mental imagery tasks. Arm-hand function was evaluated using the Utrecht Arm-Hand task and the Brunnström Fugl-Meyer Scale. Age-matched healthy individuals (N = 10) were included as controls. Results. Implicit motor imagery ability and visual motor imagery ability improved significantly at 6 weeks compared to 3 weeks poststroke. Conclusion. Our study shows that motor imagery can recover in the first weeks after stroke. This indicates that a group of patients who might not be initially selected for mental practice can, still later in the rehabilitation process, participate in mental practice programs. Moreover, our study shows that mental imagery modalities can be differently affected in individual patients and over time.

Use of mental practice to improve upper-limb recovery after stroke: a systematic review

OBJECTIVE

We sought to determine whether mental practice is an effective intervention to improve upper-limb recovery after stroke.

METHOD

We conducted a systematic review of the literature, searching electronic databases for the years 1985 to February 2009. We selected studies according to specified criteria, rated each study for level of evidence, and summarized study elements.

RESULTS

Studies differed with respect to design, patient characteristics, intervention protocols, and outcome measures. All studies used imagery of tasks involving movement of the impaired limb. The length of the interventions and number of practice hours varied. Results suggest that mental practice combined with physical practice improves upper-limb recovery.

CONCLUSION

When added to physical practice, mental practice is an effective intervention. However, generalizations are difficult to make. Further research is warranted to determine who will benefit from training, the dosing needed, the most effective protocols, whether improvements are retained, and whether mental practice affects perceived occupational performance.

Visuomotorische Imaginationstherapie in der Neglektrehabilitation – Grundlagen, Vorgehen und Falldarstellungen

Mentales Training findet vermehrt in der neurologischen Rehabilitation Einsatz. Neglekpatienten mit repräsentationalen Störungen, u. a. des eigenen Körpers, könnten von einer visuomotorischen Imaginationstherapie profitieren. Das therapeutische Vorgehen für die praktische Anwendung in der Neglektrehabilitation wird vorgestellt bezüglich (1) Patientenauswahl, (2) Testdiagnostik, (3) Messung der Imaginationsfähigkeit, (4) Psychoedukation, (5) Setting, (6) Therapiemanual, (7) Frequenz und Komplexitätsgrade, (8) Therapieprotokoll, (9) Elektromyographie sowie (10) Eigentraining. Zwei Fallbeispiele verdeutlichen wie eine visuomotorische Imaginationstherapie selbst im chronischen Krankheitsstadium zu Funktionsverbesserungen führen und bei subakutem personalem Neglekt die Körperwahrnehmung beeinflusst werden kann.

The mirror neuron system: a neural substrate for methods in stroke rehabilitation

Mirror neurons found in the premotor and parietal cortex respond not only during action execution, but also during observation of actions being performed by others. Thus, the motor system may be activated without overt movement. Rehabilitation of motor function after stroke is often challenging due to severity of impairment and poor to absent voluntary movement ability. Methods in stroke rehabilitation based on the mirror neuron system--action observation, motor imagery, and imitation--take advantage of this opportunity to rebuild motor function despite impairments, as an alternative or complement to physical therapy. Here the authors review research into each condition of practice, and discuss the relevance of the mirror neuron system to stroke recovery.

Mental practice for relearning locomotor skills

Over the past 2 decades, much work has been carried out on the use of mental practice through motor imagery for optimizing the retraining of motor function in people with physical disabilities. Although much of the clinical work with mental practice has focused on the retraining of upper-extremity tasks, this article reviews the evidence supporting the potential of motor imagery for retraining gait and tasks involving coordinated lower-limb and body movements. First, motor imagery and mental practice are defined, and evidence from physiological and behavioral studies in healthy individuals supporting the capacity to imagine walking activities through motor imagery is examined. Then the effects of stroke, spinal cord injury, lower-limb amputation, and immobilization on motor imagery ability are discussed. Evidence of brain reorganization in healthy individuals following motor imagery training of dancing and of a foot movement sequence is reviewed, and the effects of mental practice on gait and other tasks involving coordinated lower-limb and body movements in people with stroke and in people with Parkinson disease are examined. Lastly, questions pertaining to clinical assessment of motor imagery ability and training strategies are discussed.

Motor imagery to enhance recovery after subcortical stroke: who might benefit, daily dose, and potential effects

BACKGROUND

Motor imagery may enhance motor recovery after stroke.

OBJECTIVES

To estimate the proportion of patients able to perform motor imagery, the feasibility of delivery of motor imagery training (MIT), and the effects of MIT on motor recovery in an exploratory study.

METHODS

An immediate pretreatment and posttreatment single-group design was used to study 10 patients after subcortical stroke with neuromuscular weakness in the upper limb. MIT that included upper limb activities reflecting everyday tasks was provided for 10 consecutive working days. Measures included assessment of chaotic motor imagery, patient report of tolerability of MIT, Motricity Index (MI), Nine Hole Peg Test (9HPT), and quality of movement (MAL-QOM). MIT dose was changed in response to patient feedback. Graphed motor function scores were inspected visually for clinically important changes.

RESULTS

Four of the 10 patients were unable to perform motor imagery. Patient opinion was positive about the content and shaped daily dose of MIT given in two 20-minute periods separated by a 10-minute rest. Clinically important changes in motor scores were found. Four patients increased MI score (range 8-16), 3 patients increased 9HPT score (range 0.02-0.04 pegs/second), and 4 patients increased MAL-QOM score (range 0.63-1.29).

CONCLUSIONS

MIT was received positively by patients, but 40% were unable to perform imagery and interindividual variations were found on motor function.

Effects of lower limb amputation on the mental rotation of feet

What happens to the mental representation of our body when the actual anatomy of our body changes? We asked 18 able-bodied controls, 18 patients with a lower limb amputation and a patient with rotationplasty to perform a laterality judgment task. They were shown illustrations of feet in different orientations which they had to classify as left or right limb. This laterality recognition task, originally introduced by Parsons in Cognit Psychol 19:178–241, (1987), is known to elicit implicit mental rotation of the subject’s own body part. However, it can also be solved by mental transformation of the visual stimuli. Despite the anatomical changes in the body periphery of the amputees and of the rotationplasty patient, no differences in their ability to identify illustrations of their affected versus contralateral limb were found, while the group of able-bodied controls showed clear laterality effects. These findings are discussed in the context of various strategies for mental rotation versus the maintenance of an intact prototypical body structural description.

Motor imagery training in hemiplegic cerebral palsy: a potentially useful therapeutic tool for rehabilitation

Converging evidence indicates that motor deficits in cerebral palsy (CP) are related not only to problems with execution, but also to impaired motor planning. Current rehabilitation mainly focuses on alleviating compromised motor execution. Motor imagery is a promising method of training the more 'cognitive' aspects of motor behaviour, and may, therefore, be effective in facilitating motor planning in patients with CP. In this review first we present the specific motor planning problems in CP followed by a discussion of motor imagery and its use in clinical practice. Second, we present the steps to be taken before motor imagery can be used for rehabilitation of upper limb functioning in CP. Motor imagery training has been shown to be a useful addition to existing rehabilitation protocols for poststroke rehabilitation. No such study has been conducted in CP. The age at which children can reliably use motor imagery, as well as the specific way in which motor imagery training needs to be implemented, must be researched before motor imagery training can be employed in children with CP. Based on the positive results for poststroke rehabilitation, and in light of the motor problems in CP, motor imagery training may be a valuable additional tool for rehabilitation in CP.

Motor awareness in anosognosia for hemiplegia: experiments at last!

Anosognosia for hemiplegia (AHP) is the apparent inability to acknowledge contralesional paralysis, typically following right-hemisphere lesions. Here, we review studies that regard AHP as a specific deficit of motor awareness and explain its symptoms by employing an established computational model of motor control. These accounts propose that AHP arises from a breakdown in the monitoring of intended and actual movement. First, we critically examine physiological and behavioural experiments, which attempt to provide an account of AHP by verifying the presence or absence of motor intentions. We then review more recent experiments that endeavour to empirically address the hitherto unexplored role of motor intentions and internal representations of movements in AHP patients' non-veridical (illusory) awareness of movement. Finally, we consider implications of AHP research for clinical practice and the understanding of motor awareness more generally. We conclude that the false experience of movement in AHP may provide insight into what occurs when the mechanism responsible for monitoring and correcting significant discrepancies between predicted and executed actions is impaired. The system seems to continue to operate by deceiving awareness.

Transcranial magnetic stimulation to the frontal operculum and supramarginal gyrus disrupts planning of outcome-based hand-object interactions

Behavioral data suggest that goals inform the selection of motor commands during planning. We investigated the neural correlates that mediate planning of goal-oriented actions by asking 10 healthy subjects to prepare either a goal-specific movement toward a common object (a cup), with the intent of grasping-to-pour (liquid into it) or grasping-to-move (to another location) the object, or performing a non-object-oriented stimulus-response task (move a finger). Single-pulse transcranial magnetic stimulation was administered on 50% of trials to the supramarginal gyrus (SMG), anterior intraparietal sulcus, inferior frontal gyrus opercularis (IFGo), and triangularis during motor planning. Stimulation to SMG and IFGo caused a significant delay in planning goal-oriented actions but not responses to an arbitrary stimulus. Despite the delay, movement execution was not affected, suggesting that the motor plan remained intact. Our data implicate the SMG and IFGo in planning goal-oriented hand-object interactions.

Effects of Practice, Visual Loss, Limb Amputation, and Disuse on Motor Imagery Vividness

Background. The ability to generate vivid images of movements is variable across individuals and likely influenced by sensorimotor inputs. Objectives. The authors examined (1) the vividness of motor imagery in dancers and in persons with late blindness, with amputation or an immobilization of one lower limb; (2) the effects of prosthesis use on motor imagery; and (3) the temporal characteristics of motor imagery. Methods. Eleven dancers, 10 persons with late blindness, 14 with amputation, 6 with immobilization, and 2 groups of age-matched healthy individuals (27 in control group A; 35 in control group B) participated. The Kinesthetic and Visual Imagery Questionnaire served to assess motor imagery vividness. Temporal characteristics were assessed with mental chronometry. Results. The late blindness group and dance group displayed higher imagery scores than respective control groups. In the amputation and immobilization groups, imagery scores were lower on the affected side than the intact side and specifically for imagined foot movements. Imagery scores of the affected limb positively correlated with the time since walking with prosthesis. Movement times during imagination and execution (amputation and immobilization) were longer on the affected side than the intact side, but the temporal congruence between real and imagined movement times was similar to that in the control group. Conclusions. The mental representation of actions is highly modulated by imagery practice and motor activities. The ability to generate vivid images of movements can be specifically weakened by limb loss or disuse, but lack of movement does not affect the temporal characteristics of motor imagery.

Motor imagery after subcortical stroke: a functional magnetic resonance imaging study

BACKGROUND AND PURPOSE

In recovered subcortical stroke, the pattern of motor network activation during motor execution can appear normal or not, depending on the task. Whether this applies to other aspects of motor function is unknown. We used functional MRI to assess motor imagery (MI), a promising new approach to improve motor function after stroke, and contrasted it to motor execution.

METHODS

Twenty well-recovered patients with hemiparetic subcortical stroke (14 males; mean age, 66.5 years) and 17 aged-matched control subjects were studied. Extensive behavioral screening excluded 8 patients and 4 control subjects due to impaired MI abilities. Subjects performed MI and motor execution of a paced finger-thumb opposition sequence using a functional MRI paradigm that monitored compliance. Activation within the primary motor cortex (BA4a and 4p), dorsal premotor, and supplementary motor areas was examined.

RESULTS

The pattern of activation during affected-hand motor execution was not different from control subjects. Affected-hand MI activation was also largely similar to control subjects, including involvement of BA4, but with important differences: (1) unlike control subjects and the nonaffected hand, activation in BA4a and dorsal premotor was not lower during MI as compared with motor execution; (2) the hemispheric balance of BA4p activation was significantly less lateralized than control subjects; and (3) ipsilesional BA4p activation positively correlated with motor performance.

CONCLUSIONS

In well-recovered subcortical stroke, the motor system, including ipsilesional BA4, is activated during MI despite the lesion. It, however, remains disorganized in proportion to residual motor impairment. Thus, components of movement upstream from execution appear differentially affected after stroke and could be targeted by rehabilitation in more severely affected patients.

Using mental practice in stroke rehabilitation: a framework

Introduction: Motor imagery and mental practice are getting increased attention in neurological rehabilitation. Several different mental practice intervention protocols have been used in studies on its effect on recovery in stroke rehabilitation. The content of the intervention protocols itself is rarely discussed or questioned.

Objective: To give a practical framework of how mental practice could be integrated into therapy, drawing on available evidence and theory. The aim of the treatment programme described is to enhance both the patient's physical performance and their empowerment and self-determination.

The framework: Based on evidence from sports rehabilitation and our own experiences the framework will eventually be evaluated in a randomized controlled trial. Five steps are described to teach and upgrade the patient's imagery technique: (1) assess mental capacity to learn imagery technique; (2) establish the nature of mental practice; (3) teach imagery technique; (4) embed and monitor imagery technique; (5) develop self-generated treatments. The description is not, however, a recipe that should be followed precisely. It leaves enough room to tailor the mental practice intervention to the specific individual possibilities, skills and needs of the patient in accordance with evidence-based practice.

Discussion: Different aspects of the described protocol are discussed and compared with experiences from sports and evidence available in rehabilitation.

Selective motor imagery defect in patients with locked-in syndrome

Recent studies indicate that motor imagery is subserved by activation of motor information. However, at present it is not clear whether the sparing of motor efferent pathways is necessary to perform a motor imagery task. To clarify this issue, we required patients with a selective, severe de-efferentation (locked-in syndrome, LIS) to mentally manipulate hands and three-dimensional objects. Compared with normal controls, LIS patients showed a profound impairment on a modified version of the hand-laterality task and a normal performance on mental rotation of abstract items. Moreover, LIS patients did not present visuomotor compatibility effects between anatomical side of hands and spatial location of stimuli on the computer screen. Such findings confirmed that the motor system is involved in mental simulation of action but not in mental manipulation of visual images. To explain LIS patients' inability in manipulating hand representations, we suggested that the pontine lesion, both determined a complete de-efferentation, and affected a component of the motor system, which is crucial for mental representation of body parts, probably the neural connections between parietal lobes and cerebellum.