Showing papers on "Motor imagery published in 2013"

Resting state changes in functional connectivity correlate with movement recovery for BCI and robot-assisted upper-extremity training after stroke.

Abstract: Background. Robot-assisted training may improve motor function in some hemiparetic patients after stroke, but no physiological predictor of rehabilitation progress is reliable. Resting state functional magnetic resonance imaging (RS-fMRI) may serve as a method to assess and predict changes in the motor network. Objective. The authors examined the effects of upper-extremity robot-assisted rehabilitation (MANUS) versus an electroencephalography-based brain computer interface setup with motor imagery (MI EEG-BCI) and compared pretreatment and posttreatment RS-fMRI. Methods. In all, 9 adults with upper-extremity paresis were trained for 4 weeks with a MANUS shoulder-elbow robotic rehabilitation paradigm. In 3 participants, robot-assisted movement began if no voluntary movement was initiated within 2 s. In 6 participants, MI-BCI–based movement was initiated if motor imagery was detected. RS-fMRI and Fugl-Meyer (FM) upper-extremity motor score were assessed before and after training. Results. The individual gai...

Classification of Motor Imagery BCI Using Multivariate Empirical Mode Decomposition

Abstract: Brain electrical activity recorded via electroencephalogram (EEG) is the most convenient means for brain-computer interface (BCI), and is notoriously noisy. The information of interest is located in well defined frequency bands, and a number of standard frequency estimation algorithms have been used for feature extraction. To deal with data nonstationarity, low signal-to-noise ratio, and closely spaced frequency bands of interest, we investigate the effectiveness of recently introduced multivariate extensions of empirical mode decomposition (MEMD) in motor imagery BCI. We show that direct multichannel processing via MEMD allows for enhanced localization of the frequency information in EEG, and, in particular, its noise-assisted mode of operation (NA-MEMD) provides a highly localized time-frequency representation. Comparative analysis with other state of the art methods on both synthetic benchmark examples and a well established BCI motor imagery dataset support the analysis.

Near-infrared Spectroscopy–mediated Neurofeedback Enhances Efficacy of Motor Imagery–based Training in Poststroke Victims A Pilot Study

Abstract: Background and Purpose—Despite the findings that motor imagery and execution are supposed to share common neural networks, previous studies using imagery-based rehabilitation have revealed inconsistent results. In the present study, we investigated whether feedback of cortical activities (neurofeedback) using near-infrared spectroscopy could enhance the efficacy of imagery-based rehabilitation in stroke patients. Methods—Twenty hemiplegic patients with subcortical stroke received 6 sessions of mental practice with motor imagery of the distal upper limb in addition to standard rehabilitation. Subjects were randomly allocated to REAL and SHAM groups. In the REAL group, cortical hemoglobin signals detected by near-infrared spectroscopy were fed back during imagery. In the SHAM group, irrelevant randomized signals were fed back. Upper limb function was assessed using the finger and arm subscales of the Fugl-Meyer assessment and the Action Research Arm Test. Results—The hand/finger subscale of the Fugl-Meyer a...

Brain-Computer Interface in Stroke Rehabilitation

Abstract: Recent advances in computer science enabled people with severe motor disabilities to use brain-computer interfaces (BCI) for communication, control, and even to restore their motor disabilities. This paper reviews the most recent works of BCI in stroke rehabilitation with a focus on methodology that reported on data collected from stroke patients and clinical studies that reported on the motor improvements of stroke patients. Both types of studies are important as the former advances the technology of BCI for stroke, and the latter demonstrates the clinical efficacy of BCI in stroke. Finally some challenges are discussed. Category: Human computing

State-dependent effects of transcranial oscillatory currents on the motor system: what you think matters.

Abstract: Imperceptible transcranial alternating current stimulation (tACS) changes the endogenous cortical oscillatory activity in a frequency-specific manner. In the human motor system, tACS coincident with the idling beta rhythm of the quiescent motor cortex increased the corticospinal output. We reasoned that changing the initial state of the brain (i.e., from quiescence to a motor imagery task that desynchronizes the local beta rhythm) might also change the susceptibility of the corticospinal system to resonance effects induced by beta-tACS. We tested this hypothesis by delivering tACS at different frequencies (theta, alpha, beta, and gamma) on the primary motor cortex at rest and during motor imagery. Motor-evoked potentials (MEPs) were obtained by transcranial magnetic stimulation (TMS) on the primary motor cortex with an online-navigated TMS-tACS setting. During motor imagery, the increase of corticospinal excitability was maximal with theta-tACS, likely reflecting a reinforcement of working memory processes required to mentally process and "execute" the cognitive task. As expected, the maximal MEPs increase with subjects at rest was instead obtained with beta-tACS, substantiating previous evidence. This dissociation provides new evidence of state and frequency dependency of tACS effects on the motor system and helps discern the functional role of different oscillatory frequencies of this brain region. These findings may be relevant for rehabilitative neuromodulatory interventions.

Towards the integration of mental practice in rehabilitation programs. A critical review

Abstract: Many clinical studies have investigated the use of mental practice (MP) through motor imagery (MI) to enhance functional recovery of patients with diverse physical disabilities. Although beneficial effects have been generally reported for training motor functions in persons with chronic stroke (e.g., reaching, writing, walking), attempts to integrate MP within rehabilitation programs have been met with mitigated results. These findings have stirred further questioning about the value of MP in neurological rehabilitation. In fact, despite abundant systematic reviews, which customarily focused on the methodological merits of selected studies, several questions about factors underlying observed effects remain to be addressed. This review discusses these issues in an attempt to identify factors likely to hamper the integration of MP within rehabilitation programs. First, the rationale underlying the use of MP for training motor function is briefly reviewed. Second, three modes of MI delivery are proposed based on the analysis of the research protocols from 27 studies in persons with stroke and Parkinson's disease. Third, for each mode of MI delivery, a general description of MI training is provided. Fourth, the review discusses factors influencing MI training outcomes such as: the adherence to MI training, the amount of training and the interaction between physical and mental rehearsal; the use of relaxation, the selection of reliable, valid and sensitive outcome measures, the heterogeneity of the patient groups, the selection of patients and the mental rehearsal procedures. To conclude, the review proposes a framework for integrating MP in rehabilitation programs and suggests research targets for steering the implementation of MP in the early stages of the rehabilitation process. The challenge has now shifted towards the demonstration that MI training can enhance the effects of regular therapy in persons with subacute stroke during the period of spontaneous recovery.

EEG feature comparison and classification of simple and compound limb motor imagery

Abstract: Motor imagery can elicit brain oscillations in Rolandic mu rhythm and central beta rhythm, both originating in the sensorimotor cortex. In contrast with simple limb motor imagery, less work was reported about compound limb motor imagery which involves several parts of limbs. The goal of this study was to investigate the differences of the EEG patterns between simple limb motor imagery and compound limb motor imagery, and discuss the separability of multiple types of mental tasks. Ten subjects participated in the experiment involving three tasks of simple limb motor imagery (left hand, right hand, feet), three tasks of compound limb motor imagery (both hands, left hand combined with right foot, right hand combined with left foot) and rest state. Event-related spectral perturbation (ERSP), power spectral entropy (PSE) and spatial distribution coefficient were adopted to analyze these seven EEG patterns. Then three algorithms of modified multi-class common spatial patterns (CSP) were used for feature extraction and classification was implemented by support vector machine (SVM). The induced event-related desynchronization (ERD) affects more components within both alpha and beta bands resulting in more broad ERD bands at electrode positions C3, Cz and C4 during left/right hand combined with contralateral foot imagery, whose PSE values are significant higher than that of simple limb motor imagery. From the topographical distribution, simultaneous imagination of upper limb and contralateral lower limb certainly contributes to the activation of more areas on cerebral cortex. Classification result shows that multi-class stationary Tikhonov regularized CSP (Multi-sTRCSP) outperforms other two multi-class CSP methods, with the highest accuracy of 84% and mean accuracy of 70%. The work implies that there exist the separable differences between simple limb motor imagery and compound limb motor imagery, which can be utilized to build a multimodal classification paradigm in motor imagery based brain-computer interface (BCI) systems.

Modulation of event-related desynchronization in robot-assisted hand performance: brain oscillatory changes in active, passive and imagined movements.

Abstract: Robot-assisted therapy in patients with neurological disease is an attempt to improve function in a moderate to severe hemiparetic arm. A better understanding of cortical modifications after robot-assisted training could aid in refining rehabilitation therapy protocols for stroke patients. Modifications of cortical activity in healthy subjects were evaluated during voluntary active movement, passive robot-assisted motor movement, and motor imagery tasks performed under unimanual and bimanual protocols. Twenty-one channel electroencephalography (EEG) was recorded with a video EEG system in 8 subjects. The subjects performed robot-assisted tasks using the Bi-Manu Track robot-assisted arm trainer. The motor paradigm was executed during one-day experimental sessions under eleven unimanual and bimanual protocols of active, passive and imaged movements. The event-related-synchronization/desynchronization (ERS/ERD) approach to the EEG data was applied to investigate where movement-related decreases in alpha and beta power were localized. Voluntary active unilateral hand movement was observed to significantly activate the contralateral side; however, bilateral activation was noted in all subjects on both the unilateral and bilateral active tasks, as well as desynchronization of alpha and beta brain oscillations during the passive robot-assisted motor tasks. During active-passive movement when the right hand drove the left one, there was predominant activation in the contralateral side. Conversely, when the left hand drove the right one, activation was bilateral, especially in the alpha range. Finally, significant contralateral EEG desynchronization was observed during the unilateral task and bilateral ERD during the bimanual task. This study suggests new perspectives for the assessment of patients with neurological disease. The findings may be relevant for defining a baseline for future studies investigating the neural correlates of behavioral changes after robot-assisted training in stroke patients.

Introducing the revised applied model of deliberate imagery use for sport, dance, exercise, and rehabilitation

Abstract: Received May 23rd 2012 - Accepted November 4th 2012 Abstract. This article reviews literature on cognitive and motivational imagery use in the sport, exercise, dance, and rehabilitation domains and outlines a revised applied model of imagery use. The original model by Martin, Moritz, & Hall, 1999 guides practitioners and researchers in determining what cognitive and/or motivational imagery to use in a particular situation for achieving a desired outcome. The revised model proposed builds on the original version by retaining its empirically- supported "where", "when", and "why" components. Incorporating recent advancements in imagery research, the model distinguishes between what is imaged (i.e., the content) from why it is imaged (i.e., the function). The revised model also acknowledges the importance of the individual and how they interpret an image by including "who" and "meaning" components, as well as expanding on how imagery ability is likely to influence the relationship between imagery use and outcomes. Based on imagery's increased usage beyond the sport setting, this review explains how the revised model can also be applied to individuals in the exercise, dance, and rehabilitation settings. Finally, recommendations of how imagery can be effectively used and some predictions of the revised model are provided to encourage future research and application.

Does motor imagery share neural networks with executed movement: a multivariate fMRI analysis

Abstract: Introduction Motor imagery (MI) is the mental rehearsal of a motor first person action-representation. There is interest in using MI to access the motor network after stroke. Conventional fMRI modelling has shown that MI and executed movement (EM) activate similar cortical areas but it remains unknown whether they share cortical networks. Proving this is central to using MI to access the motor network and as a form of motor training. Here we use multivariate analysis (tensor independent component analysis-TICA) to map the array of neural networks involved during MI and EM. Methods Fifteen right-handed healthy volunteers (mean-age 28.4 yrs) were recruited and screened for their ability to carry out MI (Chaotic MI Assessment). fMRI consisted of an auditory-paced (1Hz) right hand finger-thumb opposition sequence (2,3,4,5; 2…) with two separate runs acquired (MI & rest and EM & rest: block design). No distinction was made between MI and EM until the final stage of processing. This allowed TICA to identify independent-components (IC) that are common or distinct to both tasks with no prior assumptions. Results TICA defined 52 ICs. Non-significant ICs and those representing artefact were excluded. Components in which the subject scores were significantly different to zero (for either EM or MI) were included. 7 independent components remained. There were IC’s shared between EM and MI involving the contralateral BA4, PMd, parietal areas and SMA. IC’s exclusive to EM involved the contralateral BA4, S1 and ipsilateral cerebellum whereas the IC related exclusively to MI involved ipsilateral BA4 and PMd. Conclusion In addition to networks specific to each task indicating a degree of independence, we formally demonstrate here for the first time that MI and EM share cortical networks. This significantly strengthens the rationale for using MI to access the motor networks, but the results also highlight important differences.

Rehabilitation is initiated early after stroke, but most motor rehabilitation trials are not: a systematic review.

Abstract: Stroke is the third most common cause of death and the most common cause of acquired adult disability in developed countries.1 Motor impairment is common after stroke, and a critical factor influencing the patient’s ability to live independently.2,3 The neurobiological mechanisms of plasticity and spontaneous recovery during the initial days and weeks after stroke have been reasonably well characterized using animal models.4,5 These mechanisms include cell genesis, functional plasticity, and structural adaptations, such as axonal sprouting and synaptogenesis. The nature and time course of these mechanisms map onto the trajectory of motor recovery observed in human patients, most of whom reach their recovery plateau within 3 months of stroke.6,7 Rehabilitation is primarily delivered in this time period, to capitalize on the unique physiological conditions that prevail, and shape the spontaneous recovery process for the patient’s benefit. Recovery of function is likely to be enhanced by novel treatments that interact with and facilitate the underlying mechanisms of spontaneous recovery. A variety of neurorehabilitation techniques aimed at improving motor recovery after stroke have been developed and trialed over the past 3 decades. These include repetitive task training, biofeedback, constraint-induced movement therapy, robotics, virtual reality, motor imagery, noninvasive brain stimulation, and pharmacological agents.8,9 However, despite almost 1000 randomized control trials (RCTs) in stroke rehabilitation,10 there is very little translation of this evidence base into clinical practice.11,12 Research efforts to develop the evidence base are challenged by difficulties in recruiting patients, resulting in small sample sizes; the heterogeneity of impairments after stroke and the complexity of their interactions with factors affecting recovery; and limited collaboration between scientists, clinicians, patient groups, and industry.11 Even when the research evidence base supports the development of clinical guidelines, significant barriers …

Enhanced Activation of Motor Execution Networks Using Action Observation Combined with Imagination of Lower Limb Movements

Abstract: The combination of first-person observation and motor imagery, i.e. first-person observation of limbs with online motor imagination, is commonly used in interactive 3D computer gaming and in some movie scenes. These scenarios are designed to induce a cognitive process in which a subject imagines himself/herself acting as the agent in the displayed movement situation. Despite the ubiquity of this type of interaction and its therapeutic potential, its relationship to passive observation and imitation during observation has not been directly studied using an interactive paradigm. In the present study we show activation resulting from observation, coupled with online imagination and with online imitation of a goal-directed lower limb movement using functional MRI (fMRI) in a mixed block/event-related design. Healthy volunteers viewed a video (first-person perspective) of a foot kicking a ball. They were instructed to observe-only the action (O), observe and simultaneously imagine performing the action (O-MI), or imitate the action (O-IMIT). We found that when O-MI was compared to O, activation was enhanced in the ventralpremotor cortex bilaterally, left inferior parietal lobule and left insula. The O-MI and O-IMIT conditions shared many activation foci in motor relevant areas as confirmed by conjunction analysis. These results show that (i) combining observation with motor imagery (O-MI) enhances activation compared to observation-only (O) in the relevant foot motor network and in regions responsible for attention, for control of goal-directed movements and for the awareness of causing an action, and (ii) it is possible to extensively activate the motor execution network using O-MI, even in the absence of overt movement. Our results may have implications for the development of novel virtual reality interactions for neurorehabilitation interventions and other applications involving training of motor tasks.

Using a Hybrid Brain Computer Interface and Virtual Reality System to Monitor and Promote Cortical Reorganization through Motor Activity and Motor Imagery Training

Abstract: Stroke is one of the leading causes of adult disability with high economical and societal costs. In recent years, novel rehabilitation paradigms have been proposed to address the life-long plasticity of the brain to regain motor function. We propose a hybrid brain-computer interface (BCI)-reality (VR) system that combines a personalized motor training in a VR environment, exploiting brain mechanisms for action execution and observation, and a neuro-feedback paradigm using mental imagery as a way to engage secondary or indirect pathways to access undamaged cortico-spinal tracts. Furthermore, we present the development and validation experiments of the proposed system. More specifically, EEG data on nine naive healthy subjects show that a simultaneous motor activity and motor imagery paradigm is more effective at engaging cortical motor areas and related networks to a larger extent. Additionally, we propose a motor imagery driven BCI-VR version of our system that was evaluated with nine different healthy subjects. Data show that users are capable of controlling a virtual avatar in a motor imagery training task that dynamically adjusts its difficulty to the capabilities of the user. User self-report questionnaires indicate enjoyment and acceptance of the proposed system.

Whatever works: a systematic user-centered training protocol to optimize brain-computer interfacing individually.

Abstract: This study implemented a systematic user-centered training protocol for a 4-class brain-computer interface (BCI). The goal was to optimize the BCI individually in order to achieve high performance within few sessions for all users. Eight able-bodied volunteers, who were initially naive to the use of a BCI, participated in 10 sessions over a period of about 5 weeks. In an initial screening session, users were asked to perform the following seven mental tasks while multi-channel EEG was recorded: mental rotation, word association, auditory imagery, mental subtraction, spatial navigation, motor imagery of the left hand and motor imagery of both feet. Out of these seven mental tasks, the best 4-class combination as well as most reactive frequency band (between 8-30 Hz) was selected individually for online control. Classification was based on common spatial patterns and Fisher’s linear discriminant analysis. The number and time of classifier updates varied individually. Selection speed was increased by reducing trial length. To minimize differences in brain activity between sessions with and without feedback, sham feedback was provided in the screening and calibration runs in which usually no real-time feedback is shown. Selected task combinations and frequency ranges differed between users. The tasks that were included in the 4-class combination most often were (1) motor imagery of the left hand (2), one brain-teaser task (word association or mental subtraction) (3), mental rotation task and (4) one more dynamic imagery task (auditory imagery, spatial navigation, imagery of the feet). Participants achieved mean performances over sessions of 44-84% and peak performances in single-sessions of 58-93% in this user-centered 4-class BCI protocol. This protocol is highly adjustable to individual users and thus could increase the percentage of users who can gain and maintain BCI control. A high priority for future work is to examine this protocol with severely disabled users.

Training Transfer: Scientific Background and Insights for Practical Application

Abstract: Training transfer as an enduring, multilateral, and practically important problem encompasses a large body of research findings and experience, which characterize the process by which improving performance in certain exercises/tasks can affect the performance in alternative exercises or motor tasks. This problem is of paramount importance for the theory of training and for all aspects of its application in practice. Ultimately, training transfer determines how useful or useless each given exercise is for the targeted athletic performance. The methodological background of training transfer encompasses basic concepts related to transfer modality, i.e., positive, neutral, and negative; the generalization of training responses and their persistence over time; factors affecting training transfer such as personality, motivation, social environment, etc. Training transfer in sport is clearly differentiated with regard to the enhancement of motor skills and the development of motor abilities. The studies of bilateral skill transfer have shown cross-transfer effects following one-limb training associated with neural adaptations at cortical, subcortical, spinal, and segmental levels. Implementation of advanced sport technologies such as motor imagery, biofeedback, and exercising in artificial environments can facilitate and reinforce training transfer from appropriate motor tasks to targeted athletic performance. Training transfer of motor abilities has been studied with regard to contralateral effects following one limb training, cross-transfer induced by arm or leg training, the impact of strength/power training on the preparedness of endurance athletes, and the impact of endurance workloads on strength/power performance. The extensive research findings characterizing the interactions of these workloads have shown positive transfer, or its absence, depending on whether the combinations conform to sport-specific demands and physiological adaptations. Finally, cross-training as a form of concurrent exercising in different athletic disciplines has been examined in reference to the enhancement of general fitness, the preparation of recreational athletes, and the preparation of athletes for multi-sport activities such as triathlon, duathlon, etc.

Motor Imagery and Aging

Abstract: Motor imagery (MI) is the mental simulation of an action without its actual execution It has been successfully used through mental practice--the repetition of imagined movements--to optimize motor function either in sport or rehabilitation settings Healthy elderly individuals facing age-related impairments in motor function could also benefit from this method of training-retraining The authors review studies that have investigated MI in physically and mentally healthy adults aged 55 years and older First, they provide an overview of the psychophysical data on MI in the elderly, which show no changes with aging in the ability to imagine simple-usual movements but reveal some age-related alterations in the mental simulation of difficult-unusual movements Second, they present emerging neuroimaging and neurostimulation data revealing that the sensorimotor system is engaged during MI in older adults Finally, the authors emphasize the potential of using mental practice as a safe and easy way to help preserving/improving motor function in the elderly and provide some recommendations for future research in this direction

Noninvasive Strategies to Promote Functional Recovery after Stroke

Abstract: Stroke is a common and disabling global health-care problem, which is the third most common cause of death and one of the main causes of acquired adult disability in many countries. Rehabilitation interventions are a major component of patient care. In the last few years, brain stimulation, mirror therapy, action observation, or mental practice with motor imagery has emerged as interesting options as add-on interventions to standard physical therapies. The neural bases for poststroke recovery rely on the concept of plasticity, namely, the ability of central nervous system cells to modify their structure and function in response to external stimuli. In this review, we will discuss recent noninvasive strategies employed to enhance functional recovery in stroke patients and we will provide an overview of neural plastic events associated with rehabilitation in preclinical models of stroke.

Layered stimulus response training improves motor imagery ability and movement execution.

Abstract: This study aimed to test Lang's bioinformational theory by comparing the effects of layered stimulus and response training (LSRT) with imagery practice on improvements in imagery ability and performance of a motor skill (golf putting) in 24 novices (age, M = 20.13 years; SD = 1.65; 12 female) low in imagery ability. Participants were randomly assigned to a LSRT (introducing stimulus and response propositions to an image in a layered approach), motor imagery (MI) practice, or visual imagery (VI) practice group. Following baseline measures of MI ability and golf putting performance, the LSRT and MI practice groups imaged successfully performing the golf putting task 5 times each day for 4 days whereas the VI practice group imaged the ball rolling into the hole. Only the LSRT group experienced an improvement in kinesthetic MI ability, MI ability of more complex skills, and actual golf putting performance. Results support bioinformational theory by demonstrating that LSRT can facilitate visual and kinesthetic MI ability and reiterate the importance of imagery ability to ensure MI is an effective prime for movement execution.

Mental images across the adult lifespan: a behavioural and fMRI investigation of motor execution and motor imagery

Abstract: Motor imagery (M.I.) is a mental state in which real movements are evoked without overt actions. There is some behavioural evidence that M.I. declines with ageing. The neurofunctional correlates of these changes have been investigated only in two studies, but none of the these studies has measured explicit correlations between behavioural variables and the brain response, nor the correlation of M.I. and motor execution (M.E.) of the same acts in ageing. In this paper, we report a behavioural and functional magnetic resonance imaging (fMRI) experiment that aimed to address this issue. Twenty-four young subjects (27 ± 5.6 years) and twenty-four elderly subjects (60 ± 4.6 years) performed two block-design fMRI tasks requiring actual movement (M.E.) or the mental rehearsal (M.I.) of finger movements. Participants also underwent a behavioural mental chronometry test in which the temporal correlations between M.I. and M.E. were measured. We found significant neurofunctional and behavioural differences between the elderly subjects and the young subjects during the M.E. and the M.I. tasks: for the M.E. task, the elderly subjects showed increased activation in frontal and prefrontal (pre-SMA) cortices as if M.E. had become more cognitively demanding; during the M.I. task, the elderly over-recruited occipito-temporo-parietal areas, suggesting that they may also use a visual imagery strategy. We also found between-group behavioural differences in the mental chronometry task: M.I. and M.E. were highly correlated in the young participants but not in the elderly participants. The temporal discrepancy between M.I. and M.E. in the elderly subjects correlated with the brain regions that showed increased activation in the occipital lobe in the fMRI. The same index was correlated with the premotor regions in the younger subjects. These observations show that healthy elderly individuals have decreased or qualitatively different M.I. compared to younger subjects.