Motor imagery ability in stroke patients: the relationship between implicit and explicit motor imagery measures

Development and validation of an open-source hand laterality judgement task for in-person and online studies

The Hand Laterality Judgement Task (HLJT) is considered a measure of the ability to manipulate motor images. The 'biomechanical constraints' effect (longer reaction times for hand rotations towards anatomically difficult versus biomechanically easier movements) is considered the behavioural hallmark indicating motor imagery is being used. Previous work has used diverse HLJT paradigms, and there is no standardized procedure for the task. We developed an open-source, freely available version of the HLJT in PsychoPy2, which needs no programming skills and is highly customisable. Some studies suggest responding to the HLJT with the hands may interfere with performance, which would limit practical application of the task. We examined this potential issue using in-person and online versions. For the in-person version, 40 right-footed/handed individuals performed the HLJT with their feet or bimanually (N = 20 each). For the online version, 60 right-handed individuals performed the task bimanually or unimanually (N = 20 each). Bayesian mixed-effect analyses quantified the evidence for and against equivalence within and between the in-person and online versions. Both versions replicated previously described behavioural phenomena, including effects of angle, hand view, and the 'biomechanical constraints' effect. While responding with different effectors modified overall reaction times, it did not interact with other factors analysed, and did not affect accuracy or the 'biomechanical constraints' effect. There was also evidence for equivalence between in-person and online bimanual groups for all measures. We conclude that this open-source, standardized HLJT protocol (available at https://osf.io/8h7ec/) can reliably detect previously identified effects and works equally well in-person or online.

A Personalized Predictor of Motor Imagery Ability Based on Multi-frequency EEG Features

A brain-computer interface (BCI) based on motor imagery (MI) provides additional control pathways by decoding the intentions of the brain. MI ability has great intra-individual variability, and the majority of MI-BCI systems are unable to adapt to this variability, leading to poor training effects. Therefore, prediction of MI ability is needed. In this study, we propose an MI ability predictor based on multi-frequency EEG features. To validate the performance of the predictor, a video-guided paradigm and a traditional MI paradigm are designed, and the predictor is applied to both paradigms. The results demonstrate that all subjects achieved > 85% prediction precision in both applications, with a maximum of 96%. This study indicates that the predictor can accurately predict the individuals' MI ability in different states, provide the scientific basis for personalized training, and enhance the effect of MI-BCI training.

Evaluating the impact of movement representation techniques on recovery outcomes in post-orthopaedic surgery individuals: a systematic review and meta-analysis

BACKGROUND

Although movement representation techniques has originally been used in neurological rehabilitation, growing researches suggests that it may also introduce advantageous effects to individuals with orthopaedic injuries. This systematic review and meta-analysis aimed to investigate the effects of these techniques on pain, range of motion, muscle strength, functional performance and fear of movement in individuals after orthopaedic surgeries.

METHOD

Five electronic databases were searched until April 2024. Two reviewers independently conducted study selection and data extraction. Randomized controlled studies containing individuals after limb surgeries were identified. The quality of enrolled studies and the overall certainty of evidence was assessed by scales, respectively. Egger's test and funnel plot were used to assess publication bias. Subgroup analysis was also conducted to explore the source of heterogeneity.

RESULTS

Twenty-one randomized controlled trials involving 659 postsurgical participants were identified. The meta-analysis suggested moderate-quality evidence of a positive effect on pain intensity (SMD=-0.85; 95% CI -1.26, -0.43; p < 0.001). A low quality of evidence pointed toward a positive effect on functional scales (SMD=-0.84, 95% CI -1.27, -0.41, p < 0.001) and range of motion (SMD = 0.8, 95% CI 0.24, 1.35, p = 0.005). The very low quality of evidence suggested a significant effect on the functional test results (SMD=-0.8, 95% CI -1.01, -0.58, p < 0.001). The results remained nonsignificant for muscle strength and fear of movement. Intervention quantity, Disability of Arm, Shoulder, and Hand (DASH) score and intervention content were the sources of heterogeneity for pain intensity, functional scale score and range of motion, respectively.

CONCLUSION

Compared with conventional rehabilitation, movement representation techniques increase pain relief, functional performance and range of motion. Our results support the use of mental practice techniques in individuals after orthopaedic surgeries, with moderate to very low-quality evidence.

REVIEW REGISTRATION

This trial was registered on PROSPERO on 10 August, 2024 (CRD42024583380).

Experience in sports and music influences motor imagery: Insights from implicit and explicit measures

BACKGROUND

Motor imagery (MI) can be an effective strategy for learning and enhancing movement or as an alternative training modality when physical practice is compromised. Individual differences in MI ability are widely documented but the role of experience in different activities in influencing MI is not well understood. The present study examined how experience in activities associated with the use of MI influences implicit and explicit MI.

METHODS

Participants completed a hand laterality judgement task (N = 84) and a MI questionnaire (MIQ-3; N = 59) online. These implicit and explicit measures of MI were analysed in relation to frequent experience in individual sports/exercise, team sports, dance, and playing a musical instrument.

RESULTS

The majority of participants reported using both visual and kinesthetic MI within their activities. Across activities, frequent experience was associated with more accurate hand laterality judgement, as well as increased biomechanical constraint effects, particularly for hands viewed from the palm. In relation to the different activity types, significant effects were found for individual and team sports and music, but not dance. Participants' level of training was associated with ratings of explicit MI (MIQ-3).

CONCLUSION

Experience in activities that utilise MI influences implicit MI, while formal training may have a stronger influence on explicit MI. Activity-specific effects on MI may reflect differences in kinesthetic and visual experience of the different hand surfaces.

Mu down regulation EEG-neurofeedback training combined to motor imagery facilitates early consolidation in a sequential finger tapping task

Objective.Motor imagery (MI) has demonstrated positive effects on motor performance and triggers activation in the motor cortex (MC). EEG-Neurofeedback (EEG-NF) is a neuromodulation technique that provides real-time feedback on one's brain activity, enabling self-regulation of brain states. While there is increasing evidence of humans controlling the activity of various brain networks, including the MC, through EEG-NF, the tangible benefits of this self-regulation on motor performance remain uncertain. This study investigates the potential benefits of EEG-NF training in explicit learning of a sequential movement, in comparison to MI training and to a combined EEG-NF and MI training.Approach.Ninety-one right-handed healthy adults were randomly assigned to one of four groups (a)NF(n= 24), (b)MI(n= 22), (c)MI + NF(n= 23) and (d)control(n= 22). Participants performed a sequential finger tapping task before and after (immediately, 20 min and 24 h) a single 30 min training session. Motor performance, movement speed and event related desynchronization data were analyzed.Main results.MI training led to a better motor performance compared to control condition immediately after training that was sustained at the 20 min retest time point (p= 0.02 and 0.05). In contrast, EEG-NF training alone did not yield better motor performance compared to control condition at any time-point (p> .05). Remarkably, only the combination of both trainings led to superior motor performance 24 h after training in comparison to control group (p= 0.02). Additionally, all experimental groups successfully decreased mu rhythm amplitude throughout most of the training.Significance.Combined EEG-NF and MI training appears particularly promising for enhancing motor consolidation holding the potential to advance rehabilitation approaches.

Transformation but not generation of motor images is disrupted following stimulation over the left inferior parietal lobe

Motor imagery (MI) involves the generation, maintenance, and transformation of motor images; yet, the neural underpinnings of each stage are not well understood. Here, we investigated the role of the left inferior parietal lobe (IPL) in the stages of MI. Healthy participants (N = 20) engaged in a MI task (making judgments about hands presented on a screen; hand laterality judgment task) over two days. Past literature demonstrates the mental rotation of hands in this task involves implicit MI (i.e., where MI occurs spontaneously in the absence of explicit instructions). During the task, active (Day A; 120% resting motor threshold) or sham (Day B; placebo) neuronavigated transcranial magnetic stimulation (TMS) was applied to the left IPL (location determined from past neuroimaging work) on 50% of trials at 250, 500, or 750ms post-stimulus onset, corresponding to different stages of MI. A/B days were randomized across participants. Linear mixed effects (LME) modelling conducted on reaction time and accuracy revealed that longer reaction times were observed when TMS was delivered at 750ms after trial onset, and more greatly for active vs. sham stimulation. This effect was exacerbated for palm-vs. back-view stimuli and for left vs. right hands. Accuracy overall was decreased for active vs. sham stimulation, and to a greater extent for palm-vs. back-view stimuli. Findings suggest that the left IPL is involved in image transformation. Overall this work informs on the neural underpinnings of the stages of MI.

A preliminary exploration of quantitative models for evaluating binocular visual perception impairments among patients diagnosed with stroke

The objective of this study is to formulate and implement graded biological models pertaining to binocular visual perception function with the use of computer algorithms. We aim to quantitatively assess the location, severity, and degree of impairment in binocular visual perception among patients who have suffered stroke, thereby providing valuable insights into the repercussions of cerebral tissue damage on the visual system. To overcome the shortcomings of previous instruments used to assess binocular function in terms of stereoscopic effects and the challenges posed by physiological and psychological interference during examinations, this study optimized its approach by integrating polarized stereovision technology with computer graphic modeling techniques. This study employed computer models to assess binocular visual perception function in stroke patients. Computer models refer to psychophysical testing methods used to measure binocular visual perception function, including various assessment tasks such as recognizing inverted letters and assessing stereopsis during high-speed movements. The cross-into-circle test was used as a means to quantify perceptual eye position. Subsequently, the collected data was analyzed to assess the magnitude of impairment in binocular visual perception. The results of the study revealed a spectrum of binocular visual perception impairment among patients diagnosed with stroke, demonstrating discernible variations in the recognition of inverted letters and stereopsis across different movement speeds. Importantly, perceptual eye position measurements offered valuable insights into ocular misalignment. The computational models effectively quantified both the spatial distribution and severity of these identified impairments. Damage to brain tissue resulting from a stroke can give rise to notable impairments in binocular visual perception function. Graded biological models, formulated through computer algorithms, provide a systematic framework for the comprehensive evaluation and quantification of these impairments. The comprehension of the nature and extent of visual impairments observed in patients with stroke establishes a basis for the development of personalized visual perception learning methodologies. Based on such tailored approaches, we aim to facilitate the recovery of impaired visual function, thereby contributing to the broader objective of neural system rehabilitation.

Assessment of Motor Imagery and Its Relationship to Functional Impairment in Post-Stroke Patients: A Descriptive Cross-Sectional Study

Background: Motor and cognitive sequelae are common in patients who have experienced a stroke. Recent advances in neuroscience have enabled the development of novel therapeutic approaches, such as motor imagery, which facilitate motor learning. The objective of this study is to examine the relationship between implicit and explicit motor imagery abilities and their correlation with functional impairment in post-stroke patients. Methods: A descriptive cross-sectional study was conducted with 36 patients who had experienced a stroke between March 2008 and March 2023. The capacity to generate both implicit and explicit motor imagery and to perform physical functions was evaluated. The relationship between implicit and explicit motor imagery measures was investigated using Pearson's correlation coefficient. The factorial structure, which encompasses the capacity to generate motor imagery, whether implicit or explicit, and physical function, was subjected to analysis. Results: A correlation was identified between the time taken to identify images and the accuracy of this process, with the right hand (R = 0.474), the left hand (R = 0.568), and the left foot (R = 0.344) all demonstrating significant associations. Additionally, a notable correlation was observed between the two subscales of the KVIQ-10 scale (R = 0.749). No association was identified between the capacity to generate implicit and explicit motor imagery. Two- and three-factor solutions were obtained for the right and left hemibodies, respectively. On both sides, accuracy in identifying images and physical function constituted a single factor, while time to generate images for both hands and feet constituted a second factor. Conclusions: In conclusion, no significant data were reported regarding the association between the capacity to generate implicit and explicit motor imagery in the studied sample. However, the ability to generate implicit motor imagery was related to physical function, suggesting that it may serve as a screening criterion for implementing specific therapeutic approaches in post-stroke patients.

Development and Validation of the Combined Action Observation and Motor Imagery Ability Questionnaire

Combined use of action observation and motor imagery (AOMI) is an increasingly popular motor-simulation intervention, which involves observing movements on video while simultaneously imagining the feeling of movement execution. Measuring and reporting participant imagery-ability characteristics are essential in motor-simulation research, but no measure of AOMI ability currently exists. Accordingly, the AOMI Ability Questionnaire (AOMI-AQ) was developed to address this gap in the literature. In Study 1, two hundred eleven participants completed the AOMI-AQ and the kinesthetic imagery subscales of the Movement Imagery Questionnaire-3 and Vividness of Motor Imagery Questionnaire-2. Following exploratory factor analysis, an 8-item AOMI-AQ was found to correlate positively with existing motor-imagery measures. In Study 2, one hundred seventy-four participants completed the AOMI-AQ for a second time after a period of 7-10 days. Results indicate a good test-retest reliability for the AOMI-AQ. The new AOMI-AQ measure provides a valid and reliable tool for researchers and practitioners wishing to assess AOMI ability.

Effectiveness of synchronous action observation and mental practice on upper extremity motor recovery after stroke

The purpose of this quasi-experimental pretest-posttest control group study was to examine the effect of group synchronous action observation/mental practice intervention compared to usual rehabilitation care on upper extremity motor recovery after stroke. The intervention group (n = 25) received usual care, consisting of a minimum of 3 hours of rehabilitation services per day, 5 days a week, plus group synchronous action observation/mental practice sessions 3 times per week and the control group (n = 26) received usual care. Outcome measures included the Kinesthetic and Visual Imagery Questionnaire Short Version (KVIQ-10), the Fugl-Meyer Assessment (FMA-UE) of affected upper extremity motor function only and The Box and Block Test (BBT). Although there were no statistically significant differences in upper extremity motor function between the two groups, a subgroup analysis of the intervention group identified statistically significant (FMA-UE: p < .001; BBT: p = .04) and Minimally Important Clinical Differences on upper extremity motor recovery between patients with behaviors demonstrating more versus less commitment to the intervention. Group synchronous action observation/mental practice is a promising intervention for patients demonstrating commitment to actively participating in the intervention to improve outcomes on upper extremity motor recovery after stroke.

Motor imagery ability in baseball players with throwing yips

The motor imagery ability is closely related to an individual's motor performance in sports. However, whether motor imagery ability is diminished in athletes with yips, in whom motor performance is impaired, is unclear. Therefore, this cross-sectional study aimed to determine whether general motor imagery ability or vividness of motor imagery specific to throwing motion is impaired in baseball players with throwing yips. The study enrolled 114 college baseball players. They were classified into three groups: 33 players in the yips group, 26 in the recovered group (previously had yips symptoms but had resolved them), and 55 in the control group. They answered the revised version of the vividness of movement imagery questionnaire (VMIQ-2), which assesses general motor imagery ability. Furthermore, they completed a questionnaire that assesses both positive and negative motor imagery vividness specific to baseball throwing. In the former, they responded to their ability to vividly imagine accurately throwing a controlled ball, whereas in the latter, they responded to the vividness of their experience of negative motor imagery associated with baseball throwing, specifically the image of a wild throw. No significant difference in the VMIQ-2 was found among the three groups. While no significant difference in the vividness of positive motor imagery for ball throwing was found in either first-person visual or kinesthetic perspectives among the three groups, the yips group exhibited significantly higher vividness of negative motor imagery than the control group in both perspectives. These results indicate that negative motor imagery specific to baseball throwing may be associated with symptoms of yips. Therefore, interventions addressing psychological aspects, such as anxiety, which are potential causes of the generation of negative motor imagery, may be necessary to alleviate the symptoms of yips.

Implicit motor imagery performance and cortical activity throughout the menstrual cycle

Studies show that female motor and visuospatial skills are modulated by the menstrual cycle. Implicit motor imagery, meaning the involuntary imagination of movements during a task, involves kinesthetic, visual, and spatial aspects of the corresponding action and can be investigated by using the hand laterality judgment task (HLJT). In this study we aimed to investigate whether implicit motor imagery performance and cortical activity are altered throughout the menstrual cycle, as demonstrated by motor skills in females. Thus, 31 healthy women underwent HLJT during the menstrual, follicular and luteal phases of their menstrual cycles. Right-handed participants had to recognize the laterality (right or left) of hands presented in different views (palm or back) and orientations on a computer screen. Test performance and EEG event-related potentials were analyzed. Participants performed better in the test in the follicular and luteal phases when compared to the menstrual phase, and the accuracy of the test was positively correlated with estradiol levels in the follicular phase. The difference between medial and lateral hand orientations for rotation-related negativity was significant in the medial and left parieto-occipital regions only in the follicular phase. These findings suggest positive modulating action of estradiol in performing implicit motor imagery.

Individual differences in processing ability to transform visual stimuli during the mental rotation task are closely related to individual motor adaptation ability

Mental rotation (MR) is a well-established experimental paradigm for exploring human spatial ability. Although MR tasks are assumed to be involved in several cognitive processes, it remains unclear which cognitive processes are related to the individual ability of motor adaptation. Therefore, we aimed to elucidate the relationship between the response time (RT) of MR using body parts and the adaptive motor learning capability of gait. In the MR task, dorsal hand, palmar plane, dorsal foot, and plantar plane images rotated in 45° increments were utilized to measure the RTs required for judging hand/foot laterality. A split-belt treadmill paradigm was applied, and the number of strides until the value of the asymmetrical ground reaction force reached a steady state was calculated to evaluate the individual motor adaptation ability. No significant relationship was found between the mean RT of the egocentric perspectives (0°, 45°, and 315°) or allocentric perspectives (135°, 180°, and 225°) and adaptive learning ability of gait, irrespective of body parts or image planes. Contrarily, the change rate of RTs obtained by subtracting the RT of the egocentric perspective from that of the allocentric perspective in dorsal hand/foot images that reflect the time to mentally transform a rotated visual stimulus correlated only with adaptive learning ability. Interestingly, the change rate of RTs calculated using the palmar and plantar images, assumed to reflect the three-dimensional transformation process, was not correlated. These findings suggest that individual differences in the processing capability of visual stimuli during the transformation process involved in the pure motor simulation of MR tasks are precisely related to individual motor adaptation ability.

The Impact of Context on EEG Motor Imagery Neurofeedback and Related Motor Domains

Neurofeedback (NF) is a versatile non-invasive neuromodulation technique. In combination with motor imagery (MI), NF has considerable potential for enhancing motor performance or supplementing motor rehabilitation. However, not all users achieve reliable NF control. While research has focused on various brain signal properties and the optimisation of signal processing to solve this issue, the impact of context, i.e. the conditions in which NF motor tasks occur, is comparatively unknown. We review current research on the impact of context on MI NF and related motor domains. We identify long-term factors that act at the level of the individual or of the intervention, and short-term factors, with levels before/after and during a session. The reviewed literature indicates that context plays a significant role. We propose considering context factors as well as within-level and across-level interactions when studying MI NF.

Feasibility of motor imagery and effects of activating and relaxing practice on autonomic functions in healthy young adults: A randomised, controlled, assessor-blinded, pilot trial

Introduction

Motor imagery (MI) is the mental rehearsal of a motor task. Between real and imagined movements, a functional equivalence has been described regarding timing and brain activation. The primary study aim was to investigate the feasibility of MI training focusing on the autonomic function in healthy young people. Further aims were to evaluate participants’ MI abilities and compare preliminary effects of activating and relaxing MI on autonomic function and against controls.

Methods

A single-blinded randomised controlled pilot trial was performed. Participants were randomised to the activating MI (1), relaxing MI (2), or control (3) group. Following a MI familiarisation, they practiced home-based kinaesthetic MI for 17 minutes, 5 times/week for 2 weeks. Participants were called once for support. The primary outcome was the feasibility of a full-scale randomised controlled trial using predefined criteria. Secondary outcomes were participants’ MI ability using the Movement Imagery Questionnaire-Revised, mental chronometry tests, hand laterality judgement and semi-structured interviews, autonomic function.

Results

A total of 35 participants completed the study. The feasibility of a larger study was confirmed, despite 35% attrition related to the COVID-19 pandemic. Excellent MI capabilities were seen in participants, and significant correlations between MI ability measures. Interview results showed that participants accepted or liked both interventions. Seven major themes and insider recommendations for MI interventions emerged. No significant differences and negligible to medium effects were observed in MI ability or autonomic function between baseline and post-intervention measures or between groups.

Conclusions

Results showed that neither activating nor relaxing MI seems to change autonomic function in healthy individuals. Further adequately powered studies are required to answer open questions remaining from this study. Future studies should investigate effects of different MI types over a longer period, to rule out habituation and assess autonomic function at several time points and simultaneously with MI.

Effectiveness of a combined transcranial direct current stimulation and virtual reality-based intervention on upper limb function in chronic individuals post-stroke with persistent severe hemiparesis: a randomized controlled trial

BACKGROUND

Functional impairments derived from the non-use of severely affected upper limb after stroke have been proposed to be mitigated by action observation and imagination-based techniques, whose effectiveness is enhanced when combined with transcranial direct current stimulation (tDCS). Preliminary studies in mildly impaired individuals in the acute phase post-stroke show intensified effects when action is facilitated by tDCS and mediated by virtual reality (VR) but the effectiveness in cases of severe impairment and chronic stroke is unknown. This study investigated the effectiveness of a combined tDCS and VR-based intervention in the sensorimotor function of chronic individuals post-stroke with persistent severe hemiparesis compared to conventional physical therapy.

METHODS

Twenty-nine participants were randomized into an experimental group, who received 30 minutes of the combined tDCS and VR-based therapy and 30 minutes of conventional physical therapy, or a control group, who exclusively received conventional physical therapy focusing on passive and active assistive range of motion exercises. The sensorimotor function of all participants was assessed before and after 25 one-hour sessions, administered three to five times a week, using the upper extremity subscale of the Fugl-Meyer Assessment, the time and ability subscales of the Wolf Motor Function Test, and the Nottingham Sensory Assessment.

RESULTS

A clinically meaningful improvement of the upper limb motor function was consistently revealed in all motor measures after the experimental intervention, but not after conventional physical therapy. Similar limited effects were detected in the sensory function in both groups.

CONCLUSION

The combined tDCS and VR-based paradigm provided not only greater but also clinically meaningful improvement in the motor function (and similar sensory effects) in comparison to conventional physical therapy.

Body representation in people with apraxia post Stroke- an observational study

Objective: To investigate how two types of body representation (body schema and body image) were affected in people with and without apraxia following a supratentorial stroke.Design: Observational cross-sectional studySetting: Level 1 Specialist Neurological Rehabilitation UnitParticipants: 30 participants post-stroke diagnosed with (n = 10) and without apraxia (n = 20) according to a modified version of the short Ideomotor Apraxia Test.Interventions: Not applicableMain Outcome Measures: Body schema assessed using the hand laterality recognition test and body part knowledge test; Implicit body image assessed using the sidedness test.Results: Left-sided lesions were more common in the apraxic group. Compared to people without apraxia post-stroke, those with apraxia showed significantly reduced accuracy and longer reaction times on the hand laterality test and fewer correct responses on the body part knowledge test. There was no between-groups difference in the sidedness test.Conclusions: People with apraxia showed deficits in online body representations (body schema) that are used to plan and execute actions. Future research studies could target body schema deficits as an adjunct in the rehabilitation of apraxia.

An Inter- and Intra-Subject Transfer Calibration Scheme for Improving Feedback Performance of Sensorimotor Rhythm-Based BCI Rehabilitation

The Brain Computer Interface (BCI) system is a typical neurophysiological application which helps paralyzed patients with human-machine communication. Stroke patients with motor disabilities are able to perform BCI tasks for clinical rehabilitation. This paper proposes an effective scheme of transfer calibration for BCI rehabilitation. The inter- and intra-subject transfer learning approaches can improve the low-precision classification performance for experimental feedback. The results imply that the systematical scheme is positive in increasing the confidence of voluntary training for stroke patients. In addition, it also reduces the time consumption of classifier calibration.

Systematic Review and Meta-Analysis of the Effectiveness of Mental Practice for the Upper Limb After Stroke: Imagined or Real Benefit?

OBJECTIVES

This systematic review sought to determine the effectiveness of mental practice (MP) on the activity limitations of the upper limb in individuals after stroke, as well as when, in whom, and how MP should be delivered.

DATA SOURCES

Ten electronic databases were searched from November 2009 to May 2020. Search terms included: Arm, Practice, Stroke rehabilitation, Imagination, Paresis, Recovery of function, and Stroke. Studies from a Cochrane review of MP (up to November 2009) were automatically included. The review was registered with the PROSPERO database of systematic reviews (reference no.: CRD42019126044).

STUDY SELECTION

Randomized controlled trials of adults after stroke using MP for the upper limb were included if they compared MP to usual care, conventional therapy, or no treatment and reported activity limitations of the upper limb as outcomes. Independent screening was conducted by 2 reviewers.

DATA EXTRACTION

One reviewer extracted data using a tool based on the Template for Intervention Description and Replication. Data extraction was independently verified by a second reviewer. Quality was assessed using the PEDro tool.

DATA SYNTHESIS

Fifteen studies (n=486) were included and 12 (n=328) underwent meta-analysis. MP demonstrated significant benefit on upper limb activities compared with usual treatment (standardized mean difference [SMD], 0.6; 95% confidence interval [CI], 0.32-0.88). Subgroup analyses demonstrated that MP was most effective in the first 3 months after stroke (SMD, 1.01; 95% CI, 0.53-1.50) and in individuals with the most severe upper limb deficits (weighted mean difference, 7.33; 95% CI, 0.94-13.72).

CONCLUSIONS

This review demonstrates that MP is effective in reducing activity limitations of the upper limb after stroke, particularly in the first 3 months after stroke and in individuals with the most severe upper limb dysfunction. There was no clear pattern of the ideal dosage of MP.

What are the determinants of explicit and implicit motor imagery ability in stroke patients?: a controlled study

Purpose: The purposes of the study were to (a) investigate both explicit and implicit motor imagery ability (MIA) impairment after stroke, (b) examine predictive effects of clinical characteristics for MIA after stroke.Materials and Methods: Forty one patients with stroke (PwS) (mean age 59.41 ± 10.19 years; %41 female) and 36 healthy participants (mean age 62.47 ± 9.29 years; %47 female) completed Chaotic Motor Imagery Assessment-Hand Rotation for implicit MIA and Movement Imagery Questionnaire-3 (MIQ-3) and Box and Block Test (BBT) for explicit MIA. The severity of motor and sensory impairments were determined by the Fugl-Meyer Assessment-Upper Extremity (FMAUE) scores. The Turkish version of Motor Activity Log-28 was used to assess amount of use (AUS) and quality of movement in daily life.Results: Our results indicated that both implicit and explicit MIA (except kinaesthetic imagery of MIQ-3) in PwS were statistically impaired compared to controls (p < 0.05). The sensorimotor impairment level, amount of use and movement quality of the affected upper limb were found to be correlated with MIA in various degrees. Total motor scores in FMAUE and AUS were significant predictors of explicit MIA (p < 0.01). Additionally, explicit MIA scores of stroke subgroups were statistically different between severely and mildly impaired patients, in favour of mildly impaired group (p < 0.05).Conclusion: In conclusion, both motor impairment level and amount of daily use of upper extremity were found to be predictive factors for explicit MIA. Further investigation with brain imaging techniques is needed to explore the validity of these findings in establishing MIA.

Can a highly accurate multi-class SSMVEP BCI induce sensory-motor rhythm in sensorimotor area?

Different visual stimuli might have different effects on the brain, e.g. the change of brightness, non-biological movement and biological movement. In this study, flicker, checkerboard, and gaiting stimuli were chosen as visual stimuli to investigate whether steady-state motion visual evoked potential (SSMVEP) effected on the sensorimotor area for rehabilitation. The gaiting stimulus was designed as the gaiting sequence of a human. The hypothesis is that only observing the designed gaiting stimulus would simultaneously induce 1) SSMVEP in the occipital area, similarly to an SSVEP stimulus; and 2) sensorimotor rhythm (SMR) in the primary sensorimotor area, because such action observation could activate the mirror neuron system. Canonical correlation analysis was used to detect SSMVEP from occipital EEG, and event-related spectral perturbation was used to identify SMR in the EEG from the sensorimotor area. The results showed that the designed gaiting stimulus-induced SSMVEP, with classification accuracies of 88.9 ± 12.0% in a four-class scenario. More importantly, it induced clear and sustained event-related desynchronization/synchronization (ERD/ERS), while no ERD/ERS could be observed when the other two SSVEP stimuli were used. Further, for participants with a sufficiently clear SSMVEP pattern (classification accuracy > 85%), the ERD index values in the mu-beta band induced by the proposed gaiting stimulus were statistically different from that of the other two types of stimulus. Therefore, a novel BCI based on the designed stimulus has potential in neurorehabilitation applications because it simultaneously has the high accuracy of an SSMVEP (~90% accuracy in a four-class setup) and the ability to activate the sensorimotor area.

Performing the hand laterality judgement task does not necessarily require motor imagery

When people judge the laterality of rotated hand images, that is they perform the laterality judgement task (LJT), they are thought to use motor imagery. However, recent studies have suggested that its completion does not necessarily require the use of motor imagery. In this study, we investigated whether and how many people preferentially use motor imagery to perform the LJT in 37 healthy adults. We assessed the presence of behavioural features associated with motor imagery at the individual level, namely, the linear angle-response time (RT) relationship and the biomechanical constraints effect in the LJT and in the same-different judgement task (SDJT), in which people are not thought to use motor imagery. We found that at most 50% of participants showed both behavioural features in the palmar view condition of the LJT. Moreover, this proportion did not differ from that in the dorsal view condition of the LJT or that in both view conditions of the SDJT. These results demonstrate that a motor imagery-based strategy is not universally and specifically used to perform the LJT. Therefore, previous results of the LJT, in particular, regarding the biomechanical constraints effect, should be reinterpreted in light of our findings.

What is the effect of bodily illusions on corticomotoneuronal excitability? A systematic review

Background

This systematic review aimed to summarise and critically appraise the evidence for the effect of bodily illusions on corticomotoneuronal excitability.

Methods

Five databases were searched, with two independent reviewers completing study inclusion, risk of bias, transcranial magnetic stimulation (TMS) reporting quality, and data extraction. Included studies evaluated the effect of an illusion that altered perception of the body (and/or its movement) on excitability of motor circuitry in healthy, adult, human participants. Studies were required to: use TMS to measure excitability and/or inhibition; report quantitative outcomes (e.g., motor evoked potentials); compare the illusion to a control or active comparison condition; evaluate that an illusion had occurred (e.g., measured illusion strength/presence).

Results

Of 2,257 studies identified, 11 studies (14 experiments) were included, evaluating kinaesthetic illusions (n = 5), a rubber hand illusion (RHI) paradigm (n = 5), and a missing limb illusion (n = 1). Kinaesthetic illusions (induced via vision/tendon vibration) increased corticomotoneuronal excitability. Conflicting effects were found for traditional, visuotactile RHIs of a static hand. However, embodying a hand and then observing it move (“self-action”) resulted in decreased corticomotoneuronal excitability and increased silent period duration (a measure of Gamma-Aminobutynic acid [GABA]_B-mediated intracortical inhibition in motor cortex), with the opposite occurring (increased excitability, decreased inhibition) when the fake hand was not embodied prior to observing movement (“other-action”). Visuomotor illusions manipulating agency had conflicting results, but in the lower risk study, illusory agency over movement resulted in a relative decrease in corticomotoneuronal excitability. Last, an illusion of a missing limb reduced corticomotoneuronal excitability.

Conclusion

While evidence for the effect of bodily illusions on corticomotoneuronal excitability was limited (only 14 experiments) and had a high risk of bias, kinaesthetic illusions and illusions of embodying a hand (and seeing it move), had consistent effects. Future investigations into the role of embodiment and the illusion strength on corticomotoneuronal excitability and inhibition are warranted.

Disruption of motor imagery performance following inhibition of the left inferior parietal lobe

The left inferior parietal lobe (IPL), a brain region localized to the ventro-dorsal stream, is known to be critical to motor imagery (MI) performance. Yet its specific role in processes underlying MI, namely the generation, maintenance, manipulation, and controllability of motor images, is conflicting in the literature. To determine the specific role of the left IPL in MI, the current study sought to examine the effect inhibition of the left IPL has on performance on two disparate measures thought to probe different MI processes within the same participants. Participants (N = 31) completed the hand laterality judgment task (HLJT), employed to probe processes related to manipulation and controllability, and mental chronometry, employed to probe processes related to generation and maintenance, after receiving either inhibitory transcranial magnetic stimulation to the left IPL (Active-TMS group), or with the coil angled away from the scalp (Sham group). Impaired performance on the HLJT was observed following active TMS relative to sham. Similar mental chronometry performance resulted regardless of left IPL inhibition. In showing that inhibition of the left IPL selectively disrupted performance on the HLJT but not mental chronometry, our findings indicate that the left IPL is specifically involved in image manipulation and controllability during MI. Ultimately, the current study extends our understanding of the role of the left IPL in MI.

Combined action observation and motor imagery therapy: a novel method for post-stroke motor rehabilitation

Cerebral vascular accidents (strokes) are a leading cause of motor deficiency in millions of people worldwide. While a complex range of biological systems is affected following a stroke, in this paper we focus primarily on impairments of the motor system and the recovery of motor skills. We briefly review research that has assessed two types of mental practice, which are currently recommended in stroke rehabilitation. Namely, action observation (AO) therapy and motor imagery (MI) training. We highlight the strengths and limitations in both techniques, before making the case for combined action observation and motor imagery (AO + MI) therapy as a potentially more effective method. This is based on a growing body of multimodal brain imaging research showing advantages for combined AO + MI instructions over the two separate methods of AO and MI. Finally, we offer a series of suggestions and considerations for how combined AO + MI therapy could be employed in neurorehabilitation.

A Brain-Computer Interface-Based Action Observation Game That Enhances Mu Suppression

Action observation training based on the theory of activation of the mirror-neuron system has been used for the rehabilitation of patients with stroke. In this paper, we sought to assess whether a brain-computer interface (BCI)-based action observation rehabilitation game, using a flickering action video, could preferentially activate the mirror-neuron system. Feedback of stimulus observation, evoked by the flickering action video, was provided using steady state visually evoked potential and event-related desynchronization. Fifteen healthy subjects have experienced the game with BCI interaction (game and interaction), without BCI interaction (game without interaction), observed non-flickering stimuli, and flickering stimuli without the game background (stimuli only) in a counter-balanced order. The game and interface condition was resulted in significantly stronger activation of the mirror-neuron system than did the other three conditions. In addition, the amount of mirror-neuron system activation is gradually decreased in the game without interface, non-flickering stimuli, and stimuli only conditions in a time-dependent manner; however, in the game and interface condition, the amount of mirror-neuron system activation was maintained until the end of the training. Taken together, these data suggest that the proposed game paradigm, which integrates the action observation paradigm with BCI technology, could provide interactive responses for whether watching video clips can engage patients and enhance rehabilitation.

Motor Imagery Impairment in Postacute Stroke Patients

Not much is known about how well stroke patients are able to perform motor imagery (MI) and which MI abilities are preserved after stroke. We therefore applied three different MI tasks (one mental chronometry task, one mental rotation task, and one EEG-based neurofeedback task) to a sample of postacute stroke patients (n = 20) and age-matched healthy controls (n = 20) for addressing the following questions: First, which of the MI tasks indicate impairment in stroke patients and are impairments restricted to the paretic side? Second, is there a relationship between MI impairment and sensory loss or paresis severity? And third, do the results of the different MI tasks converge? Significant differences between the stroke and control groups were found in all three MI tasks. However, only the mental chronometry task and EEG analysis revealed paresis side-specific effects. Moreover, sensitivity loss contributed to a performance drop in the mental rotation task. The findings indicate that although MI abilities may be impaired after stroke, most patients retain their ability for MI EEG-based neurofeedback. Interestingly, performance in the different MI measures did not strongly correlate, neither in stroke patients nor in healthy controls. We conclude that one MI measure is not sufficient to fully assess an individual's MI abilities.

Embodied neurofeedback with an anthropomorphic robotic hand

Neurofeedback-guided motor imagery training (NF-MIT) has been suggested as a promising therapy for stroke-induced motor impairment. Whereas much NF-MIT research has aimed at signal processing optimization, the type of sensory feedback given to the participant has received less attention. Often the feedback signal is highly abstract and not inherently coupled to the mental act performed. In this study, we asked whether an embodied feedback signal is more efficient for neurofeedback operation than a non-embodiable feedback signal. Inspired by the rubber hand illusion, demonstrating that an artificial hand can be incorporated into one’s own body scheme, we used an anthropomorphic robotic hand to visually guide the participants’ motor imagery act and to deliver neurofeedback. Using two experimental manipulations, we investigated how a participant’s neurofeedback performance and subjective experience were influenced by the embodiability of the robotic hand, and by the neurofeedback signal’s validity. As pertains to embodiment, we found a promoting effect of robotic-hand embodiment in subjective, behavioral, electrophysiological and electrodermal measures. Regarding neurofeedback signal validity, we found some differences between real and sham neurofeedback in terms of subjective and electrodermal measures, but not in terms of behavioral and electrophysiological measures. This study motivates the further development of embodied feedback signals for NF-MIT.

Do Motor Imagery Performances Depend on the Side of the Lesion at the Acute Stage of Stroke?

Motor imagery has been considered a substitute for overt motor execution to study post-stroke motor recovery. However, motor imagery abilities at the acute stage (<3 weeks) are poorly known. The aim of this study was to compare explicit and implicit motor imagery abilities in stroke patients and healthy subjects, correlate them with motor function, and investigate the role of right or left hemisphere lesions on performance. Twenty-four stroke patients at the acute stage and 24 age- and gender-matched healthy volunteers performed implicit (Hand Laterality Judgment Task) and explicit (number of imagined/executed hand movements) motor imagery tasks and a clinical motor assessment. Differences between healthy subjects and patients as well as the impact of lesion side on motor imagery were studied using ANOVA. We analyzed the relationship between motor executed and imagined movements (temporal congruence) using Pearson correlations. Our study shows that for implicit imagery, stroke patients had slower reaction times [RTs, t(46) = 1.7, p = 0.02] and higher error rates for the affected hand [t(46) = 3.7, p < 0.01] yet shared similar characteristics [angle effect: F(1,46) = 30.8, p ≤ 0.0001] with respect to healthy subjects. For the unaffected hand, right-sided stroke patients had a higher error rate and similar RTs whereas left sided stroke had higher RTs but similar error rate than healthy subjects. For explicit imagery, patients exhibited bilateral deficits compared to healthy subjects in the executed and imagined condition (p < 0.0001). Patients and healthy subjects exhibited a temporal congruence between executed and imagined movements (p ≤ 0.04) except for right-sided strokes who had no correlation for both hands. When using motor imagery as a tool for upper limb rehabilitation early after stroke, caution must be taken related to the side of the lesion.

Damage to Fronto-Parietal Networks Impairs Motor Imagery Ability after Stroke: A Voxel-Based Lesion Symptom Mapping Study

Background: Mental practice with motor imagery has been shown to promote motor skill acquisition in healthy subjects and patients. Although lesions of the common motor imagery and motor execution neural network are expected to impair motor imagery ability, functional equivalence appears to be at least partially preserved in stroke patients.

Aim: To identify brain regions that are mandatory for preserved motor imagery ability after stroke.

Method:Thirty-seven patients with hemiplegia after a first time stroke participated. Motor imagery ability was measured using a Motor Imagery questionnaire and temporal congruence test. A voxelwise lesion symptom mapping approach was used to identify neural correlates of motor imagery in this cohort within the first year post-stroke.

Results: Poor motor imagery vividness was associated with lesions in the left putamen, left ventral premotor cortex and long association fibers linking parieto-occipital regions with the dorsolateral premotor and prefrontal areas. Poor temporal congruence was otherwise linked to lesions in the more rostrally located white matter of the superior corona radiata.

Conclusion: This voxel-based lesion symptom mapping study confirms the association between white matter tract lesions and impaired motor imagery ability, thus emphasizing the importance of an intact fronto-parietal network for motor imagery. Our results further highlight the crucial role of the basal ganglia and premotor cortex when performing motor imagery tasks.

Comparing self-report and mental chronometry measures of motor imagery ability

The present study investigated the relationship between two of the most common measures of motor imagery ability, self-report ratings, and chronometric assessment. This was done for three types of imagery modalities: external visual imagery (EVI), internal visual imagery (IVI), and kinesthetic imagery (KI). Measures of imagery ability (i.e. self-report and mental chronometry) were also compared across skill levels. Participants (N = 198) completed the Movement Imagery Questionnaire-3 (MIQ-3) to generate self-report ratings. Chronometric assessment was obtained by recording the duration of each MIQ-3 movement imaged and physically performed and then calculating a discrepancy score. There were no significant correlations between self-report and mental chronometry for any of the three motor imagery types (p > .05). When assessing the different types of motor imagery ability using self-report ratings, elite athletes had significantly higher KI than IVI, which was in turn significantly higher than EVI (p < .05). When assessing motor imagery ability using mental chronometry, there were no significant differences in imagery type (p > .05). Findings suggest both measures address different components of MI quality and should be used together to obtain a more comprehensive assessment of motor imagery ability.