Motor Imagery

Rehabilitation with mental practice has similar effects on mobility as rehabilitation with relaxation in people with Parkinson's disease: a multicentre randomised trial

QUESTIONS

Is mental practice embedded in standard physiotherapy compared with relaxation embedded in standard physiotherapy more effective at improving mobility tasks in people with Parkinson's disease in the community? Does disease severity influence the treatment effect?

DESIGN

A multicentre randomised controlled trial.

PARTICIPANTS

People with Parkinson's disease.

INTERVENTION

During a six-week intervention period, both groups received physiotherapy as usual with the addition of either mental practice (experimental group) or relaxation (control group). Imagery skills were taught using a four-step protocol. Movement imagery (in thought) and the performance of motor activities were combined.

OUTCOME MEASURES

Outcomes were assessed at six weeks and three months with: the patient- and therapist-perceived effect on walking performance (visual analogue scale), the Timed Up and Go test, and the 10 m Walk test. Primary analysis was performed using intention-totreat and was repeated as a per-protocol analysis, and as a sub-group analysis of participants with Hoehn and Yahr stage of less than 3. Generalised estimating equations were used to analyse effects.

RESULTS

47 participants were assigned to the control (n = 22) and experimental (n = 25) groups. No effect in favour of the mental practice intervention on any outcome measure could be detected at any of the measurement points. In the sub-group analysis of participants with milder disease, the experimental group improved more than the control group but this was not statistically significant.

CONCLUSION

In this study, we did not find differences between embedded mental practice and relaxation with current standard of care.

TRIAL REGISTRATION

Nederlands Trial Register: NTR1735.

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.

Cognitive context determines dorsal premotor cortical activity during hand movement in patients after stroke

BACKGROUND AND PURPOSE

Stroke patients often have difficulties in simultaneously performing a motor and cognitive task. Functional imaging studies have shown that movement of an affected hand after stroke is associated with increased activity in multiple cortical areas, particularly in the contralesional hemisphere. We hypothesized patients for whom executing simple movements demands greater selective attention will show greater brain activity during movement.

METHODS

Eight chronic stroke patients performed a behavioral interference test using a visuo-motor tracking with and without a simultaneous cognitive task. The magnitude of behavioral task decrement under cognitive motor interference (CMI) conditions was calculated for each subject. Functional MRI was used to assess brain activity in the same patients during performance of a visuo-motor tracking task alone; correlations between CMI score and movement-related brain activation were then explored.

RESULTS

Movement-related activation in the dorsal precentral gyrus of the contralesional hemisphere correlated strongly and positively with CMI score (r(2) at peak voxel=0.92; P<0.05). Similar but weaker relationships were observed in the ventral precentral and middle frontal gyrus. There was no independent relationship between hand motor impairment and CMI.

CONCLUSIONS

Results suggest that variations in the degree to which a cognitive task interferes with performance of a concurrent motor task explains a substantial proportion of the variations in movement-related brain activity in patients after stroke. The results emphasize the importance of considering cognitive context when interpreting brain activity patterns and provide a rationale for further evaluation of integrated cognitive and movement interventions for rehabilitation in stroke.

Critical issues in state-of-the-art brain-computer interface signal processing

This paper reviews several critical issues facing signal processing for brain-computer interfaces (BCIs) and suggests several recent approaches that should be further examined. The topics were selected based on discussions held during the 4th International BCI Meeting at a workshop organized to review and evaluate the current state of, and issues relevant to, feature extraction and translation of field potentials for BCIs. The topics presented in this paper include the relationship between electroencephalography and electrocorticography, novel features for performance prediction, time-embedded signal representations, phase information, signal non-stationarity, and unsupervised adaptation.

Clinical study of neurorehabilitation in stroke using EEG-based motor imagery brain-computer interface with robotic feedback

This clinical study investigates the ability of hemiparetic stroke patients in operating EEG-based motor imagery brain-computer interface (MI-BCI). It also assesses the efficacy in motor improvements on the stroke-affected upper limb using EEG-based MI-BCI with robotic feedback neurorehabilitation compared to robotic rehabilitation that delivers movement therapy. 54 hemiparetic stroke patients with mean age of 51.8 and baseline Fugl-Meyer Assessment (FMA) 14.9 (out of 66, higher = better) were recruited. Results showed that 48 subjects (89%) operated EEG-based MI-BCI better than at chance level, and their ability to operate EEG-based MI-BCI is not correlated to their baseline FMA (r=0.358). Those subjects who gave consent are randomly assigned to each group (N=11 and 14) for 12 1-hour rehabilitation sessions for 4 weeks. Significant gains in FMA scores were observed in both groups at post-rehabilitation (4.5, 6.2; p=0.032, 0.003) and 2-month post-rehabilitation (5.3, 7.3; p=0.020, 0.013), but no significant differences were observed between groups (p=0.512, 0.550). Hence, this study showed evidences that a majority of hemiparetic stroke patients can operate EEG-based MI-BCI, and that EEG-based MI-BCI with robotic feedback neurorehabilitation is effective in restoring upper extremities motor function in stroke.

Post-acute stroke patients use brain-computer interface to activate electrical stimulation

Through certain mental actions, our electroencephalogram (EEG) can be regulated to operate a brain-computer interface (BCI), which translates the EEG patterns into commands that can be used to operate devices such as prostheses. This allows paralyzed persons to gain direct brain control of the paretic limb, which could open up many possibilities for rehabilitative and assistive applications. When using a BCI neuroprosthesis in stroke, one question that has surfaced is whether stroke patients are able to produce a sufficient change in EEG that can be used as a control signal to operate a prosthesis.

Movement therapy induced neural reorganization and motor recovery in stroke: a review

This paper is a review conducted to provide an overview of accumulated evidence on contemporary rehabilitation methods for stroke survivors. Loss of functional movement is a common consequence of stroke for which a wide range of interventions has been developed. Traditional therapeutic approaches have shown limited results for motor deficits as well as lack evidence for their effectiveness. Stroke rehabilitation is now based on the evidence of neuroplasticity, which is responsible for recovery following stroke. The neuroplastic changes in the structure and function of relevant brain areas are induced primarily by specific rehabilitation methods. The therapeutic method which induces neuroplastic changes, leads to greater motor and functional recovery than traditional methods. Further, the recovery is permanent in nature. During the last decade various novel stroke rehabilitative methods for motor recovery have been developed. This review focuses on the methods that have evidence of associated cortical level reorganization, namely task-specific training, constraint-induced movement therapy, robotic training, mental imaging, and virtual training. All of these methods utilize principles of motor learning. The findings from this review demonstrated convincing evidence both at the neural and functional level in response to such therapies. The main aim of the review was to determine the evidence for these methods and their application into clinical practice.

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.

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.

Compromised motor planning and Motor Imagery in right Hemiparetic Cerebral Palsy

We investigated whether motor planning problems in people with Hemiparetic Cerebral Palsy (HCP) are paralleled by impaired ability to use Motor Imagery (MI). While some studies have shown that individuals with HCP can solve a mental rotation task, it was not clear if they used MI or Visual Imagery (VI). In the present study, motor planning and MI were examined in individuals with right HCP (n=10) and controls. Motor planning was measured using an object manipulation task, where participants had to anticipate the end of the motor action. MI was measured using a mental rotation paradigm, where participants judged laterality of hands presented from a back view and a palm view. To test if participants used MI or VI we compared reaction times of lateral versus medial rotations, under the assumption that MI is subject to biomechanical constraints of rotated hands, but VI is not. Individuals with HCP had a higher proportion of task failures due to inappropriate grip choice, exemplifying impaired planning. Second, individuals with HCP did not show a reaction time difference between lateral and medial rotations, indicating an impaired ability to use MI. These findings show that compromised motor planning in HCP is paralleled by an impairment in the ability to use MI. Training of MI may be a useful entry-point for rehabilitation of motor planning problems.

Brain oscillatory activity during motor imagery in EEG-fMRI coregistration

The purpose of the present work was to investigate the correlation between topographical changes in brain oscillatory activity and the blood oxygenation level-dependent (BOLD) signal during a motor imagery (MI) task using electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) coregistration. EEG was recorded in 7 healthy subjects inside a 1.5 T MR scanner during the imagination of the kinesthetic experience of movement. A Fast Fourier Transform was applied to EEG signal in the rest and active conditions. We used the event-related-synchronization (ERS)/desynchronization (ERD) approach to characterize where the imagination of movement produces a decrease in alpha and beta power. The mean alpha map showed ERD decrease localized over the contralateral sensory motor area (SM1c) and a light desynchronization in the ipsilateral sensory motor area (SM1i); whereas the mean beta map showed ERD decrease over the supplementary motor area (SMA). fMRI showed significant activation in SMA, SM1c, SM1i. The correlation is negative in the contralateral side and positive in the ipsilateral side. Using combined EEG-fMRI signals we obtained useful new information on the description of the changes in oscillatory activity in alpha and beta bands during MI and on the investigation of the sites of BOLD activity as possible sources in generating these rhythms. By correlating BOLD and ERD/ERS we may identify more accurately which regions contribute to changes of the electrical response.

Guided Motor Imagery in Healthy Adults and Stroke: Does Strategy Matter?

Background. Motor imagery (MI) enhances physical performance and skill acquisition in healthy and neurorehabilitation populations, yet little is known about the use of strategies to guide MI. Objectives. To examine the relative effectiveness of visual, auditory, and combined (visual + auditory) cueing of an imagined finger abduction task on corticomotor excitability. Methods. A total of 15 young (20-35 years) and 15 older people (over 55 years) and 10 people with chronic stroke, who could make voluntary movements of selected muscles, participated. Motor evoked potentials (MEPs, primary outcome) were measured following transcranial magnetic stimulation applied while participants imagined abducting their index finger under guidance of cueing strategies. Amplitudes of the MEPs from the first dorsal interosseous (FDI), abductor pollicis brevis (APB), and abductor digiti minimi (ADM) muscles were compared with rest, contrasted with MEPs elicited during active task performance, and expressed relative to rest to reflect facilitation. Results. Cued MI enhanced MEPs in all groups, preferentially to the target FDI muscle. In stroke, APB was also facilitated. ADM was least affected by cueing. Analyses of simple effects of condition on FDI MEPs in each group revealed that visual cueing was most effective in young people, whereas auditory cueing was most effective in healthy older people and when directed at the nonparetic side in stroke ( P < .04). On the paretic side, strategies were equally effective. In all cases, MEPs were largest during physical performance. Conclusions. Cued MI augments corticomotor excitability associated with healthy and paretic muscles related to the imagined task. Age should be considered when selecting a cueing strategy for maximum effectiveness.

Combining Brain-Computer Interfaces and Assistive Technologies: State-of-the-Art and Challenges

In recent years, new research has brought the field of electroencephalogram (EEG)-based brain–computer interfacing (BCI) out of its infancy and into a phase of relative maturity through many demonstrated prototypes such as brain-controlled wheelchairs, keyboards, and computer games. With this proof-of-concept phase in the past, the time is now ripe to focus on the development of practical BCI technologies that can be brought out of the lab and into real-world applications. In particular, we focus on the prospect of improving the lives of countless disabled individuals through a combination of BCI technology with existing assistive technologies (AT). In pursuit of more practical BCIs for use outside of the lab, in this paper, we identify four application areas where disabled individuals could greatly benefit from advancements in BCI technology, namely, “Communication and Control”, “Motor Substitution”, “Entertainment”, and “Motor Recovery”. We review the current state of the art and possible future developments, while discussing the main research issues in these four areas. In particular, we expect the most progress in the development of technologies such as hybrid BCI architectures, user–machine adaptation algorithms, the exploitation of users’ mental states for BCI reliability and confidence measures, the incorporation of principles in human–computer interaction (HCI) to improve BCI usability, and the development of novel BCI technology including better EEG devices.

Feasibility of a mental practice intervention in stroke patients in nursing homes; a process evaluation

Background

Within a multi-centre randomised controlled trial in three nursing homes, a process evaluation of a mental practice intervention was conducted. The main aims were to determine if the intervention was performed according to the framework and to describe the therapists' and participants' experiences with and opinions on the intervention.

Methods

The six week mental practice intervention was given by physiotherapists and occupational therapists in the rehabilitation teams and consisted of four phases: explanation of imagery, teaching patients how to use imagery, using imagery as part of therapy, and facilitating the patient in using it alone and for new tasks. It had a mandatory and an optional part. Data were collected by means of registration forms, pre structured patient files, patient logs and self-administered questionnaires.

Results

A total of 14 therapists and 18 patients with stroke in the sub acute phase of recovery were involved. Response rates differed per assessment (range 57-93%). Two patients dropped out of the study (total n = 16). The mandatory part of the intervention was given to 11 of 16 patients: 13 received the prescribed amount of mental practice and 12 practiced unguided outside of therapy. The facilitating techniques of the optional part of the framework were partly used. Therapists were moderately positive about the use of imagery in this specific sample. Although it was more difficult for some patients to generate images than others, all patients were positive about the intervention and reported perceived short term benefits from mental practice.

Conclusions

The intervention was less feasible than we hoped. Implementing a complex therapy delivered by existing multi-professional teams to a vulnerable population with a complex pathology poses many challenges.

What do brain lesions tell us about theories of embodied semantics and the human mirror neuron system?

Recent work has been mixed with respect to the notion of embodied semantics, which suggests that processing linguistic stimuli referring to motor-related concepts recruits the same sensorimotor regions of cortex involved in the execution and observation of motor acts or the objects associated with those acts. In this study, we asked whether lesions to key sensorimotor regions would preferentially impact the comprehension of stimuli associated with the use of the hand, mouth or foot. Twenty-seven patients with left-hemisphere strokes and 10 age- and education-matched controls were presented with pictures and words representing objects and actions typically associated with the use of the hand, mouth, foot or no body part at all (i.e., neutral). Picture/sound pairs were presented simultaneously, and participants were required to press a space bar only when the item pairs matched (i.e., congruent trials). We conducted two different analyses: 1) we compared task performance of patients with and without lesions in several key areas previously implicated in the putative human mirror neuron system (i.e., Brodmann areas 4/6, 1/2/3, 21 and 44/45), and 2) we conducted Voxel-based Lesion-Symptom Mapping analyses (VLSM; Bates et al., 2003) to identify additional regions associated with the processing of effector-related versus neutral stimuli. Processing of effector-related stimuli was associated with several regions across the left hemisphere, and not solely with premotor/motor or somatosensory regions. We also did not find support for a somatotopically-organized distribution of effector-specific regions. We suggest that, rather than following the strict interpretation of homuncular somatotopy for embodied semantics, these findings support theories proposing the presence of a greater motor-language network which is associated with, but not restricted to, the network responsible for action execution and observation.

Feasibility of a new application of noninvasive Brain Computer Interface (BCI): a case study of training for recovery of volitional motor control after stroke

BACKGROUND/PURPOSE

A large proportion of individuals with stroke have persistent deficits for which current interventions have not restored normal motor behavior. Noninvasive brain computer interfaces (BCIs) have potential advantages for restoration of function. There are also potential advantages for combining BCI with functional electrical stimulation (FES). We tested the feasibility of combined BCI + FES for motor learning after stroke.

CASE DESCRIPTION

The participant was a 43-year-old woman who was 10 months post-stroke. She was unable to produce isolated movement of any of the digits of her involved hand. With effort she exhibited simultaneous mass hyperextension of metacarpal phalangeal joints of all four fingers and thumb with simultaneous flexion of proximal interphalangeal and distal interphalangeal joints of all fingers.

INTERVENTION

Brain signals from the lesioned hemisphere were used to trigger FES for movement practice. The BCI + FES intervention consisted of trials of either attempted finger movement and relax conditions or imagined finger movement and relax conditions. The training was performed three times per week for three weeks (nine sessions total).

OUTCOME

: The participant exhibited highly accurate control of brain signal in the first session for attempted movement (97%), imagined movement (83%), and some difficulties with attempted relaxation (65%). By session 6, control of relaxation (deactivation of brain signal) improved to >80%. After nine sessions (three per week) of BCI + FES intervention, the participant demonstrated recovery of volitional isolated index finger extension.

DISCUSSION

BCI + FES training for motor learning after stroke was feasible. A highly accurate brain signal control was achieved, and this signal could be reliably used to trigger the FES device for isolated index finger extension. With training, volitional control of isolated finger extension was attained in a small number of sessions. The source of motor recovery could be attributable to BCI, FES, combined BCI + FES, or whole arm or hand motor task practice.

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.

Locomotor imagery training improves gait performance in people with chronic hemiparetic stroke: a controlled clinical trial

OBJECTIVE

The purpose of this study was to evaluate whether locomotor imagery training leads to clinical improvements in gait after stroke.

DESIGN

Pretest-posttest matched control design.

PARTICIPANTS

A total of 24 people with chronic hemiparetic stroke (13 for experimental and 11 for control) were recruited in this study.

INTERVENTIONS

The subjects in the experimental group participated in videotape-based locomotor imagery training five days a week for four weeks. They also conducted regular physical therapy.

OUTCOME MEASURES

Kinematic gait parameters were collected using a three-dimensional motion analysis system. Functional gait performance was assessed using clinical measures: Activities-specific Balance Confidence Scale, Berg Balance Test, Dynamic Gait Index and modified Emory Functional Ambulation Profile.

RESULTS

After training, walking velocity increased 0.07 +/- 0.06 m/s in the experimental group and 0.01 +/- 0.07 m/s in the control group. In the experimental group, the affected and less affected limb stride lengths increased by 0.09 +/- 0.12 m and 0.10 +/- 0.07 m respectively, whereas in the control group they decreased by 0.00 +/- 0.04 m and increased by 0.02 +/- 0.06 m, respectively. Kinematic parameters in the lower extremity joints during walking were more improved after the training in the experimental group. Confidence in balance, postural control, dynamic balance and performance time for different environmental walking situations were also improved more in the experimental group.

CONCLUSION

Locomotor imagery training can be considered as a useful option for restoration of ambulation for individuals with chronic hemiparetic stroke who are unable to participate in physical gait training.

Mental rotation task of hands: differential influence number of rotational axes

Various studies on the hand laterality judgment task, using complex sets of stimuli, have shown that the judgments during this task are dependent on bodily constraints. More specific, these studies showed that reaction times are dependent on the participant’s posture or differ for hand pictures rotated away or toward the mid-sagittal plane (i.e., lateral or medial rotation, respectively). These findings point to the use of a cognitive embodied process referred to as motor imagery. We hypothesize that the number of axes of rotation of the displayed stimuli during the task is a critical factor for showing engagement in a mental rotation task, with an increased number of rotational axes leading to a facilitation of motor imagery. To test this hypothesis, we used a hand laterality judgment paradigm in which we manipulated the difficulty of the task via the manipulation of the number of rotational axes of the shown stimuli. Our results showed increased influence of bodily constraints for increasing number of axes of rotation. More specifically, for the stimulus set containing stimuli rotated over a single axis, no influence of biomechanical constraints was present. The stimulus sets containing stimuli rotated over more than one axes of rotation did induce the use of motor imagery, as a clear influence of bodily constraints on the reaction times was found. These findings extend and refine previous findings on motor imagery as our results show that engagement in motor imagery critically depends on the used number of axes of rotation of the stimulus set.

A clinical study of motor imagery-based brain-computer interface for upper limb robotic rehabilitation

Non-invasive EEG-based motor imagery brain-computer interface (MI-BCI) holds promise to effectively restore motor control to stroke survivors. This clinical study investigates the effects of MI-BCI for upper limb robotic rehabilitation compared to standard robotic rehabilitation. The subjects are hemiparetic stroke patients with mean age of 50.2 and baseline Fugl-Meyer (FM) score 29.7 (out of 66, higher = better) randomly assigned to each group respectively (N = 8 and 10). Each subject underwent 12 sessions of 1-hour rehabilitation for 4 weeks. Significant gains in FM scores were observed in both groups at post-rehabilitation (4.9, p = 0.001) and 2-month post-rehabilitation (4.9, p = 0.002). The experimental group yielded higher 2-month post-rehabilitation gain than the control (6.0 versus 4.0) but no significance was found (p = 0.475). However, among subjects with positive gain (N = 6 and 7), the initial difference of 2.8 between the two groups was increased to a significant 6.5 (p = 0.019) after adjustment for age and gender. Hence this study provides evidence that BCI-driven robotic rehabilitation is effective in restoring motor control for stroke.

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.

Cortical activity during motor execution, motor imagery, and imagery-based online feedback

Imagery of motor movement plays an important role in learning of complex motor skills, from learning to serve in tennis to perfecting a pirouette in ballet. What and where are the neural substrates that underlie motor imagery-based learning? We measured electrocorticographic cortical surface potentials in eight human subjects during overt action and kinesthetic imagery of the same movement, focusing on power in "high frequency" (76-100 Hz) and "low frequency" (8-32 Hz) ranges. We quantitatively establish that the spatial distribution of local neuronal population activity during motor imagery mimics the spatial distribution of activity during actual motor movement. By comparing responses to electrocortical stimulation with imagery-induced cortical surface activity, we demonstrate the role of primary motor areas in movement imagery. The magnitude of imagery-induced cortical activity change was approximately 25% of that associated with actual movement. However, when subjects learned to use this imagery to control a computer cursor in a simple feedback task, the imagery-induced activity change was significantly augmented, even exceeding that of overt movement.

Sleep contribution to motor memory consolidation: a motor imagery study

STUDY OBJECTIVES

Sleep is known to enhance performance following physical practice (PP) of a new sequence of movements. Apart from a pilot study, it is still unknown whether a similar sleep-dependent consolidation effect can be observed following motor imagery (MI) and whether this mnemonic process is related to MI speed.

DESIGN

Counterbalanced within-subject design.

SETTING

The laboratory.

PARTICIPANTS

Thirty-two participants.

INTERVENTIONS

PP, real-time MI, fast MI, and NoSleep (control) groups.

MEASUREMENTS AND RESULTS

Subjects practiced an explicitly known sequence of finger movements, and were assigned to PP, real-time MI, or fast MI, in which they intentionally imagined the sequence at a faster pace. A NoSleep group subjected to real-time MI, but without any intervening sleep, was also tested. Performance was evaluated before practice, as well as prior to, and after a night of sleep or a similar time interval during the daytime. Compared with the NoSleep group, the results revealed offline gains in performance after sleep in the PP, real-time MI, and fast MI groups. There was no correlation between a measure of underestimation of the time to imagine the motor sequence and the actual speed gains after sleep, neither between the ease/difficulty to form mental images and performance gains.

CONCLUSIONS

These results provide evidence that sleep contributes to the consolidation of motor sequence learning acquired through MI and further suggests that offline delayed gains are not related to the MI content per se. They extend our previous findings and strongly confirm that performance enhancement following MI is sleep dependent.

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.

An Evaluation of a Movement Imagery Training Scheme

Movement imagery has become an important tool in a variety of fields but individual differences in imagery ability mean that some participants, with weak imagery abilities, may not be able to engage in imagery tasks or programs. In this article we present an evaluation of a training scheme designed to improve movement imagery ability. The scheme lasted 4 weeks, involving four individual training sessions lasting 1–1 1/2 hours each and homework. The scheme emphasized relaxation and kinaesthetic awareness, external and internal perspective movement imagery, prospective action judgments, and motorically driven perceptual decisions. Ten participants, of mean age 35 ( SD = 11.97), participated in the training scheme and 12 participants, of mean age 35.33 ( SD = 13.38), participated in the control group. The performance of the trainee group was compared to the performance of the control group on a series of visual and movement imagery measures, completed before and after training. In comparison to controls, trainees improved significantly on a number of key measures of movement imagery ability but did not improve on any measure of visual imagery ability. The results demonstrated that explicit and implicit aspects of movement imagery ability can be improved through imagery training.

Online performance evaluation of motor imagery BCI with augmented-reality virtual hand feedback

The online performance of a motor imagery-based Brain-Computer Interface (MI-BCI) influences its effectiveness and usability in real-world clinical applications such as the restoration of motor control. The online performance depends on factors such as the different feedback techniques and motivation of the subject. This paper investigates the online performance of the MI-BCI with an augmented-reality (AR) 3D virtual hand feedback. The subject experiences the interaction with 3D virtual hands, which have been superimposed onto his real hands and displayed on the computer monitor from a first person point-of-view. While performing motor imagery, he receives continuous visual feedback from the MI-BCI in the form of different degrees of reaching and grasping actions of the 3D virtual hands with other virtual objects. The AR feedback is compared with the conventional horizontal bar feedback on 8 subjects, of whom 7 are BCI-naïve. The subjects found the AR feedback to be more engaging and motivating. Despite the higher mental workload involved in the AR feedback, their online MI-BCI performance compared to the conventional horizontal bar feedback was not affected. The results provide motivation to further develop and refine the AR feedback protocol for MI-BCI.

Imagined self-motion differs from perceived self-motion: evidence from a novel continuous pointing method

BACKGROUND

The extent to which actual movements and imagined movements maintain a shared internal representation has been a matter of much scientific debate. Of the studies examining such questions, few have directly compared actual full-body movements to imagined movements through space. Here we used a novel continuous pointing method to a) provide a more detailed characterization of self-motion perception during actual walking and b) compare the pattern of responding during actual walking to that which occurs during imagined walking.

METHODOLOGY/PRINCIPAL FINDINGS

This continuous pointing method requires participants to view a target and continuously point towards it as they walk, or imagine walking past it along a straight, forward trajectory. By measuring changes in the pointing direction of the arm, we were able to determine participants' perceived/imagined location at each moment during the trajectory and, hence, perceived/imagined self-velocity during the entire movement. The specific pattern of pointing behaviour that was revealed during sighted walking was also observed during blind walking. Specifically, a peak in arm azimuth velocity was observed upon target passage and a strong correlation was observed between arm azimuth velocity and pointing elevation. Importantly, this characteristic pattern of pointing was not consistently observed during imagined self-motion.

CONCLUSIONS/SIGNIFICANCE

Overall, the spatial updating processes that occur during actual self-motion were not evidenced during imagined movement. Because of the rich description of self-motion perception afforded by continuous pointing, this method is expected to have significant implications for several research areas, including those related to motor imagery and spatial cognition and to applied fields for which mental practice techniques are common (e.g. rehabilitation and athletics).

Motor imagery after stroke: relating outcome to motor network connectivity

OBJECTIVE

Neuroplasticity is essential for recovery after stroke and is the target for new stroke therapies. During recovery from subcortical motor stroke, brain activations associated with movement may appear normal despite residual functional impairment. This raises an important question: how far does recovery of motor performance depend on the processes that precede movement execution involving the premotor and prefrontal cortex, rather than recovery of the corticospinal system alone?

METHODS

We examined stroke patients with functional magnetic resonance imaging while they either imagined or executed a finger-thumb opposition sequence. In addition to classical analyses of regional activations, we studied neuroplasticity in terms of differential network connectivity using structural equation modeling. The study included 8 right-handed patients who had suffered a left-hemisphere subcortical ischemic stroke with paresis, and 13 age-matched healthy controls.

RESULTS

With good functional recovery, the regional activations had returned to normal in patients. However, connectivity within the extended motor network remained abnormal. These abnormalities were seen predominantly during motor imagery and correlated with motor performance.

INTERPRETATION

Our results indicate that neuroplasticity can manifest itself as differences in connectivity among cortical areas remote from the infarct, rather than in the degree of regional activation. Connection strengths between nodes of the cortical motor network correlate with motor outcome. The altered organization of connectivity of the prefrontal areas may reflect the role of the prefrontal cortex in higher order planning of movement. Our results are relevant to the assessment and understanding of emerging physical and neurophysiological therapies for stroke rehabilitation.

Comparison of embedded and added motor imagery training in patients after stroke: study protocol of a randomised controlled pilot trial using a mixed methods approach

BACKGROUND

Two different approaches have been adopted when applying motor imagery (MI) to stroke patients. MI can be conducted either added to conventional physiotherapy or integrated within therapy sessions. The proposed study aims to compare the efficacy of embedded MI to an added MI intervention. Evidence from pilot studies reported in the literature suggests that both approaches can improve performance of a complex motor skill involving whole body movements, however, it remains to be demonstrated, which is the more effective one.

METHODS/DESIGN

A single blinded, randomised controlled trial (RCT) with a pre-post intervention design will be carried out. The study design includes two experimental groups and a control group (CG). Both experimental groups (EG1, EG2) will receive physical practice of a clinical relevant motor task ('Going down, laying on the floor, and getting up again') over a two week intervention period: EG1 with embedded MI training, EG2 with MI training added after physiotherapy. The CG will receive standard physiotherapy intervention and an additional control intervention not related to MI. The primary study outcome is the time difference to perform the task from pre to post-intervention. Secondary outcomes include level of help needed, stages of motor task completion, degree of motor impairment, balance ability, fear of falling measure, motivation score, and motor imagery ability score. Four data collection points are proposed: twice during baseline phase, once following the intervention period, and once after a two week follow up. A nested qualitative part should add an important insight into patients' experience and attitudes towards MI. Semi-structured interviews of six to ten patients, who participate in the RCT, will be conducted to investigate patients' previous experience with MI and their expectations towards the MI intervention in the study. Patients will be interviewed prior and after the intervention period.

DISCUSSION

Results will determine whether embedded MI is superior to added MI. Findings of the semi-structured interviews will help to integrate patient's expectations of MI interventions in the design of research studies to improve practical applicability using MI as an adjunct therapy technique.

Brain activity during visual versus kinesthetic imagery: an fMRI study

Although there is ample evidence that motor imagery activates similar cerebral regions to those solicited during actual movements, it is still unknown whether visual (VI) and kinesthetic imagery (KI) recruit comparable or distinct neural networks. The present study was thus designed to identify, through functional magnetic resonance imaging at 3.0 Tesla in 13 skilled imagers, the cerebral structures implicated in VI and KI. Participants were scanned in a perceptual control condition and while physically executing or focusing during motor imagery on either the visual or kinesthetic components of an explicitly known sequence of finger movements. Subjects' imagery abilities were assessed using well-established psychological, chronometric, and new physiological measures from the autonomic nervous system. Compared with the perceptual condition, physical executing, VI, and KI resulted in overlapping (albeit non-identical) brain activations, including motor-related regions and the inferior and superior parietal lobules. By contrast, a divergent pattern of increased activity was observed when VI and KI were compared directly: VI activated predominantly the occipital regions and the superior parietal lobules, whereas KI yielded more activity in motor-associated structures and the inferior parietal lobule. These results suggest that VI and KI are mediated through separate neural systems, which contribute differently during processes of motor learning and neurological rehabilitation.

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.

Effect of motor imagery in the rehabilitation of burn patients

Although there is ample evidence that motor imagery (MI) improves motor performance after CNS injury, it is still unknown whether MI may enhance motor recovery after peripheral injury and most especially in the rehabilitation of burn patients. This study aimed to investigate the effects of a 2-week MI training program combined with conventional rehabilitation on the recovery of motor functions in handed burn patients. Fourteen patients admitted to the Medical Burn Center were requested to take part in the study and were randomly assigned to the imagery or the control group. Behavioral data related to the ability to perform each successive step of three manual motor sequences were collected at five intervals during the medical procedure. The results provided evidence that MI may facilitate motor recovery, and the belief in the effectiveness of MI was strong in all patients. MI may substantially contribute to improve the efficacy of conventional rehabilitation programs. Hence, this technique should be considered as a reliable alternative method to help burn patients to recover motor functions.

A new discriminative common spatial pattern method for motor imagery brain-computer interfaces

Event-related desynchronization/synchronization patterns during right/left motor imagery (MI) are effective features for an electroencephalogram-based brain-computer interface (BCI). As MI tasks are subject-specific, selection of subject-specific discriminative frequency components play a vital role in distinguishing these patterns. This paper proposes a new discriminative filter bank (FB) common spatial pattern algorithm to extract subject-specific FB for MI classification. The proposed method enhances the classification accuracy in BCI competition III dataset IVa and competition IV dataset IIb. Compared to the performance offered by the existing FB-based method, the proposed algorithm offers error rate reductions of 17.42% and 8.9% for BCI competition datasets III and IV, respectively.

Mirror Therapy in Complex Regional Pain Syndrome Type 1 of the Upper Limb in Stroke Patients

Background. Complex regional pain syndrome type 1 (CRPSt1) of the upper limb is a painful and debilitating condition, frequent after stroke, and interferes with the rehabilitative process and outcome. However, treatments used for CRPSt1 of the upper limb are limited. Objective. This randomized controlled study was conducted to compare the effectiveness on pain and upper limb function of mirror therapy on CRPSt1 of upper limb in patients with acute stroke. Methods. Of 208 patients with first episode of unilateral stroke admitted to the authors’ rehabilitation center, 48 patients with CRPSt1 of the affected upper limb were enrolled in a randomized controlled study, with a 6-month follow-up, and assigned to either a mirror therapy group or placebo control group. The primary end points were a reduction in the visual analogue scale score of pain at rest, on movement, and brush-induced tactile allodynia. The secondary end points were improvement in motor function as assessed by the Wolf Motor Function Test and Motor Activity Log. Results. The mean scores of both the primary and secondary end points significantly improved in the mirror group ( P < .001). No statistically significant improvement was observed in any of the control group values ( P > .001). Moreover, statistically significant differences after treatment ( P < .001) and at the 6-month follow-up were found between the 2 groups. Conclusions. The results indicate that mirror therapy effectively reduces pain and enhances upper limb motor function in stroke patients with upper limb CRPSt1.

Modulation of stimulus-induced 20-Hz activity during lower extremity motor imagery

Using magnetoencephalography, we measured 20-Hz activity induced after the common peroneal nerve (CPN) stimulation in 15 healthy subjects during the execution of foot movement or its motor imagery, and examined whether the 20-Hz activity is suppressed during motor imagery of foot movement. The prominent 20-Hz activity was contralaterally induced in the paracentral area after CPN stimulation, and it was almost completely suppressed during execution of the foot movement and partially suppressed during its motor imagery. These results suggest that the modulation of the 20-Hz activity is a useful indicator of the motor imagery of foot movement.