Activation processes during mental practice in stroke patients

Unexpected Terrain Induced Changes in Cortical Activity in Bipedal-Walking Rats

Simple Summary

Most studies on cortical dynamics during walking require subjects to walk stably on specific terrain. In fact, humans or other animals are often disturbed by an abrupt change in terrains during walking. To study the impact of unexpected terrain on cortical activity, we analyzed the kinematics and electroencephalography (EEG) dynamics of bipedal-walking rats after encountering unexpected terrain. We found that the gait of rats after encountering the unexpected terrain were significantly different from normal walking. Furthermore, the activities of the left and right primary motor areas (M1), the left and right primary somatosensory areas (S1), and the retrosplenial area (RSP) are coupled to gait cycle phase and varied with the terrain conditions. These findings suggest that unexpected terrains induced changes in gait and cortical activity, and provide novel insights into cortical dynamics during walking.

Abstract

Humans and other animals can quickly respond to unexpected terrains during walking, but little is known about the cortical dynamics in this process. To study the impact of unexpected terrains on brain activity, we allowed rats with blocked vision to walk on a treadmill in a bipedal posture and then walk on an uneven area at a random position on the treadmill belt. Whole brain EEG signals and hind limb kinematics of bipedal-walking rats were recorded. After encountering unexpected terrain, the θ band power of the bilateral M1, the γ band power of the left S1, and the θ to γ band power of the RSP significantly decreased compared with normal walking. Furthermore, when the rats left uneven terrain, the β band power of the bilateral M1 and the α band power of the right M1 decreased, while the γ band power of the left M1 significantly increased compared with normal walking. Compared with the flat terrain, the θ to low β (3–20 Hz) band power of the bilateral S1 increased after the rats contacted the uneven terrain and then decreased in the single- or double- support phase. These results support the hypothesis that unexpected terrains induced changes in cortical activity.

Neurofeedback learning for mental practice rather than repetitive practice improves neural pattern consistency and functional network efficiency in the subsequent mental motor execution

During brain modulation, repeated mental practice may not always result in efficient learning. Particularly, the effectiveness of mental motor practice depends on how well one induces neural activity in a desired state consistently across mental trials, which calls for feedbacks to adjust one's performance. We hypothesized that even a brief experience of neurofeedback learning enhances trial-by-trial neural pattern consistency during subsequent mental motor execution and that this experience would change recruitment of functional connectivity in the motor imagery and default mode networks. To test this hypothesis, we conducted an experiment with two sessions of mental motor practice before and after a neurofeedback training session, in which participants conducted four types of first-person mental motor execution tasks (walking forward, turning left, turning right, and touching a tree). During the neurofeedback training session, in which participants conducted a virtual navigation game, 10 experimental participants received real-time fMRI neuro-feedbacks, while 10 control participants simply repeated the same mental task according to given cues without feedbacks. The experimental group showed significantly higher effects of neuro-feedback training on trial-by-trial consistencies and classification accuracies of activated neural patterns than the control group. Task-performing global node strength and network efficiency were increased in the motor imagery network but decreased in the default mode network only in the experimental group. These results demonstrate that even a brief experience of feedback learning is more effective than simple practice repetitions without evaluation, which was reflected in increased neural pattern consistency and task-dependent functional connectivity during a mental motor execution task.

Physiotherapy based on problem-solving in upper limb function and neuroplasticity in chronic stroke patients: A case series

RATIONALE, AIMS, AND OBJECTIVES

Upper limb recovery is one of the main concerns of stroke neurorehabilitation. Neuroplasticity might underlie such recovery, particularly in the chronic phase. The purpose of this study was to assess the effect of physiotherapy based on problem-solving in recovering arm function in chronic stroke patients and explore its neuroplastic changes.

METHODS

A small sample research design with a n of 3 using a pre-post test design was carried out. Neuroplasticity and function were assessed by using functional magnetic resonance imaging (during motor imagery and performance), action research arm test, motor assessment scale, and Fugl-Meyer assessment scale, at 3 sequential time periods: baseline(m0-before a 4-week period without physiotherapy), pre-treatment(m1), and post-treatment(m2). Minimal clinical important differences and a recovery score were assessed. Assessors were blinded to moment assignment. Patients¹ underwent physiotherapy sessions, 50 minutes, 5 days/week for 4 weeks. Four control subjects served as a reference for functional magnetic resonance imaging changes.

RESULTS

All patients recovered more than 20% after intervention. Stroke patients had similar increased areas as healthy subjects during motor execution but not during imagination at baseline. Consequently, all patients increased activity in the contralateral precentral area after intervention.

CONCLUSIONS

This study indicates that 4 weeks of physiotherapy promoted the recovery of arm function and neuroplasticity in all chronic stroke patients. Future research is recommended to determine the efficacy of this therapy.

Functional inter-cortical connectivity among motor-related cortices during motor imagery: A magnetoencephalographic study

Neural connectivity was measured during motor imagery (MI) and motor execution (ME) using magnetoencephalography in nine healthy subjects, MI, and at rest. Lower coherence values during ME and MI between sensorimotor areas than at rest, and lower values during MI between the left supplementary motor area and inferior frontal gyrus than ME suggested the sensorimotor network of MI functioned with similar connectivity to ME and that the inhibitory activity functioned continuously during MI, respectively.

Improvement in Upper Limb Motor Performance following Stroke: The Use of Mental Practice

Mental practice is a technique that involves imagery and rehearsal of movement without movement actually occurring. This study considers the evidence that indicates whether mental practice is successful in improving upper limb motor performance after a stroke. The use of mental practice in the traditional fields of sport, music and dance is identified and a theoretical premise for its application in stroke rehabilitation is presented. Eight studies on the use of mental practice in the rehabilitation of motor performance following a stroke are critiqued. These studies suggest that mental practice improves upper limb motor ability and appears to be applicable to a range of participants, especially those with moderate impairment, although good cognitive and communication skills are required.

The article suggests reasons that this relatively new approach should be considered by occupational therapists involved in stroke rehabilitation. The limited number of studies and small sample sizes are highlighted. Further research is recommended in order to identify people who will benefit from mental practice, to investigate the generalisation of results and to establish guidelines for the effective provision of mental practice in terms of length, format and content in stroke rehabilitation.

Imagery Improves Upper Extremity Motor Function in Chronic Stroke Patients: A Pilot Study

After medical stabilization, stroke patients receive rehabilitation during a period that is considered subacute. The traditional view of neurologic rehabilitation is that it reduces impairment and minimizes disability. However, intensive rehabilitation is expensive and there are limited and diminishing financial resources to pay for therapy after stroke. Imagery improves motor learning and performance. Studies report increased blood flow, electromyographic activity during imagery, and subsequent changes in organization of the motor cortex in stroke patients following imagery. Since these events usually precede reacquisition of function, it has been suggested that imagery may be beneficial in reacquisition of function following stroke. To test this, 8 chronic stroke patients with right-arm hemiparesis were provided a four-week program combining occupational therapy and imagery (OT + I), while 8 controls received a program consisting only of OT. Scores on the upper extremity section of the Fugl-Meyer Assessment of Sensorimotor Recovery indicated that those receiving OT + I exhibited significantly more improved function than those receiving OT ( F [1,14] −14.71; p < .05). Findings suggest that imagery may be an inexpensive, noninvasive compliment to OT for hemiparesis in stroke. The researchers encourage further investigation of OT + I in stroke.

The effect of visual feedback plus mental practice on symmetrical weight-bearing training in people with hemiparesis

Objective: To investigate the effect of visual feedback with mental practice on symmetrical weight-bearing training in three individuals with hemiparetic stroke.

Design: A single-subject experimental design, alternating with multiple baselines across individuals.

Setting: Laboratory of a department of occupational therapy.

Participants: Three individuals with left hemiparesis from stroke.

Intervention: Visual feedback with mental practice on symmetrical weight-bearing training.

Main outcome measures: The proportion of the participant's weight-bearing by the affected limb while standing was measured using Limloader.

Results: For participants 1, 2 and 3, the respective average weight-bearing proportions of the affected limb were 27%, 31% and 21% at baseline, 47%, 48% and 47% after visual feedback with mental practice, and 42%, 48% and 42% after visual feedback only, immediately following each training session. When the participants had visual feedback with mental practice, they placed a greater proportion of their weight on the affected limb, and this effect was maintained for 1 h.

Conclusion: These findings indicate that the visual feedback approach alone can effect improvement but visual feedback together with mental practice produces further positive effect on improving and maintaining a symmetrical stance posture in people with hemiparetic stroke.

The adjunctive role of mental practice in the rehabilitation of the upper limb after hemiplegic stroke: a pilot studya

Objective: To assess the feasibility and practicalities of using the technique of mental practice as an adjunct in the rehabilitation of the upper limb following stroke.

Design: A series of single-case studies.

Setting: A stroke rehabilitation unit in Belfast.

Subjects: Fourteen patients admitted for rehabilitation of their first stroke: six men and four women, aged 45–81 between 10 and 176 days post stroke.

Intervention: Each patient underwent a single-case design, with two weeks baseline, two weeks intervention and one week withdrawal. The intervention consisted of structured daily mental practice sessions of a reach and grasp task, in addition to their usual therapy.

Main outcome measures: The upper limb component of the Motricity Index was used to grade motor activity sequentially across the timescale of the study.

Results: Of the 14 patients recruited, four withdrew and 10 completed the study. Nine showed improvement in upper limb Motricity Index score with mental practice as measured by the two-band standard deviation method. One of these cases demonstrated an unstable baseline such that changes could not be attributed to intervention.

Conclusions: This pilot study suggests that mental practice may be useful as an adjunct to physiotherapy after stroke.

The Potential for Utilizing the “Mirror Neurone System” to Enhance Recovery of the Severely Affected Upper Limb Early after Stroke: A Review and Hypothesis

Recovery of upper limb movement control after stroke might be enhanced by repetitive goal-directed functional activities. Providing such activity is challenging in the presence of severe paresis. A possible new approach is based on the discovery of mirror neurons in the monkey cortical area F5, which are active both in observing and executing a movement. Indirect evidence for a comparable human “mirror neurone system” is provided by functional imaging. The primary motor cortex, the premotor cortex, other brain areas, and muscles appropriate for the action being observed are probably activated in healthy volunteers observing another’s movement. These findings raise the hypothesis that observation of another’s movement might train the movement execution system of stroke patients who have severe paresis to bring them to the point at which they could actively participate in rehabilitation consisting of goal-directed activities. The point of providing an observation therapy would be to facilitate the voluntary production of movement; therefore, the condition of interest would be observation with intent to imitate. However, there is as yet insufficient evidence to enable the testing of this hypothesis in stroke patients. Studies in normal subjects are needed to determine which brain sites are activated in response to observation with intent to imitate. Studies in stroke subjects are needed to determine how activation is affected after damage to different brain areas. The information from such studies should aid identification of those stroke patients who might be most likely to benefit from observation to imitate and therefore guide phase I clinical studies.

Effects of proprioception training with exercise imagery on balance ability of stroke patients

[Purpose] The purpose of the present study was to examine and compare the effects of proprioceptive training accompanied by motor imagery training and general proprioceptive training on the balance of stroke patients. [Subjects and Methods] Thirty-six stroke patients were randomly assigned to either an experimental group of 18 patients or a control group of 18 patients. The experimental group was given motor imagery training for 5 minutes and proprioceptive training for 25 minutes, while the control group was given proprioceptive training for 30 minutes. Each session and training program was implemented 5 times a week for 8 weeks. The Korean version of the Berg Balance Scale (K-BBS), Timed Up and Go test (TUG), weight bearing ratio (AFA-50, Alfoots, Republic of Korea), and joint position sense error (Dualer IQ Inclinometer, JTECH Medical, USA) were measured. [Results] Both groups showed improvements in K-BBS, TUG, weight bearing ratio, and joint position sense error. The measures of the experimental group showed greater improvement than the control group. [Conclusion] Motor imagery training, which is not subject to time restrictions, is not very risky and can be used as an effective treatment method for improving the balance ability of stroke patients.

Mental practice--triggered electrical stimulation in chronic, moderate, upper-extremity hemiparesis after stroke

OBJECTIVE

To determine the feasibility and impact of home-based, mental practice-triggered electrical stimulation among stroke survivors exhibiting moderate upper-extremity (UE) impairment.

METHOD

Five participants with moderate, stable UE hemiparesis were administered the Fugl-Meyer Assessment, the Box and Block Test, and the Activities of Daily Living, Hand Function, and overall recovery domains of the Stroke Impact Scale (Version 3). They were then administered an 8-wk regimen consisting of 1 hr of mental practice-triggered electrical stimulation every weekday in their home. At the end of every 2 wk, participants attended supervised stimulation to progress therapeutic exercises and stimulation levels and monitor compliance.

RESULTS

Six instances of device noncompliance were reported. Participants exhibited reduced UE motor impairment and increased UE dexterity and participation in valued activities.

CONCLUSION

The regimen appears feasible and had a substantial impact on UE impairment, dexterity, and participation in valued activities as well as perceptions of recovery.

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

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

Effect of overground training augmented by mental practice on gait velocity in chronic, incomplete spinal cord injury

OBJECTIVE

To compare the efficacy of a regimen combining mental practice (MP) with overground training (OT) with the efficacy of a regimen consisting of OT only on gait velocity and lower extremity motor outcomes in individuals with chronic (>12mo postinjury), incomplete spinal cord injury (SCI).

DESIGN

Randomized, controlled, single-blinded study.

SETTING

Outpatient rehabilitation laboratories.

PARTICIPANTS

Subjects with chronic, incomplete SCI (N=18).

INTERVENTIONS

Subjects were randomly assigned to receive (1) OT only, occurring 3d/wk for 8 weeks; or (2) OT augmented by MP (MP + OT), during which randomly assigned subjects listened to an MP audio recording directly after OT sessions.

MAIN OUTCOME MEASURES

Subjects were administered a test of gait velocity as well as the Tinetti Performance Oriented Mobility Assessment, Spinal Cord Injury Independence Measure, and Satisfaction With Life Scale on 2 occasions before intervention, 1 week after intervention, and 12 weeks after intervention.

RESULTS

A significant increase in gait velocity was exhibited across subjects at both 1 week posttherapy (P=.005) and at 12 weeks posttherapy (P=.006). However, no differences were seen in intervention response at either 1 or 12 weeks postintervention among subjects in the MP + OT group versus the OT-only group.

CONCLUSIONS

OT was associated with significant gains in gait velocity, and these gains were not augmented by further addition of MP.

Applying a brain-computer interface to support motor imagery practice in people with stroke for upper limb recovery: a feasibility study

BACKGROUND

There is now sufficient evidence that using a rehabilitation protocol involving motor imagery (MI) practice in conjunction with physical practice (PP) of goal-directed rehabilitation tasks leads to enhanced functional recovery of paralyzed limbs among stroke sufferers. It is however difficult to confirm patient engagement during an MI in the absence of any on-line measure. Fortunately an EEG-based brain-computer interface (BCI) can provide an on-line measure of MI activity as a neurofeedback for the BCI user to help him/her focus better on the MI task. However initial performance of novice BCI users may be quite moderate and may cause frustration. This paper reports a pilot study in which a BCI system is used to provide a computer game-based neurofeedback to stroke participants during the MI part of a protocol.

METHODS

The participants included five chronic hemiplegic stroke sufferers. Participants received up to twelve 30-minute MI practice sessions (in conjunction with PP sessions of the same duration) on 2 days a week for 6 weeks. The BCI neurofeedback performance was evaluated based on the MI task classification accuracy (CA) rate. A set of outcome measures including action research arm test (ARAT) and grip strength (GS), was made use of in assessing the upper limb functional recovery. In addition, since stroke sufferers often experience physical tiredness, which may influence the protocol effectiveness, their fatigue and mood levels were assessed regularly.

RESULTS

Positive improvement in at least one of the outcome measures was observed in all the participants, while improvements approached a minimal clinically important difference (MCID) for the ARAT. The on-line CA of MI induced sensorimotor rhythm (SMR) modulation patterns in the form of lateralized event-related desynchronization (ERD) and event-related synchronization (ERS) effects, for novice participants was in a moderate range of 60-75% within the limited 12 training sessions. The ERD/ERS change from the first to the last session was statistically significant for only two participants.

CONCLUSIONS

Overall the crucial observation is that the moderate BCI classification performance did not impede the positive rehabilitation trends as quantified with the rehabilitation outcome measures adopted in this study. Therefore it can be concluded that the BCI supported MI is a feasible intervention as part of a post-stroke rehabilitation protocol combining both PP and MI practice of rehabilitation tasks. Although these findings are promising, the scope of the final conclusions is limited by the small sample size and the lack of a control group.

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.

Using mental practice in stroke rehabilitation: a framework

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

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

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

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

Motor imagery and action observation: cognitive tools for rehabilitation

Rehabilitation, for a large part may be seen as a learning process where old skills have to be re-acquired and new ones have to be learned on the basis of practice. Active exercising creates a flow of sensory (afferent) information. It is known that motor recovery and motor learning have many aspects in common. Both are largely based on response-produced sensory information. In the present article it is asked whether active physical exercise is always necessary for creating this sensory flow. Numerous studies have indicated that motor imagery may result in the same plastic changes in the motor system as actual physical practice. Motor imagery is the mental execution of a movement without any overt movement or without any peripheral (muscle) activation. It has been shown that motor imagery leads to the activation of the same brain areas as actual movement. The present article discusses the role that motor imagery may play in neurological rehabilitation. Furthermore, it will be discussed to what extent the observation of a movement performed by another subject may play a similar role in learning. It is concluded that, although the clinical evidence is still meager, the use of motor imagery in neurological rehabilitation may be defended on theoretical grounds and on the basis of the results of experimental studies with healthy subjects.

Mental Practice in Chronic Stroke

BACKGROUND AND PURPOSE

Mental practice (MP) of a particular motor skill has repeatedly been shown to activate the same musculature and neural areas as physical practice of the skill. Pilot study results suggest that a rehabilitation program incorporating MP of valued motor skills in chronic stroke patients provides sufficient repetitive practice to increase affected arm use and function. This Phase 2 study compared efficacy of a rehabilitation program incorporating MP of specific arm movements to a placebo condition using randomized controlled methods and an appropriate sample size. Method- Thirty-two chronic stroke patients (mean=3.6 years) with moderate motor deficits received 30-minute therapy sessions occurring 2 days/week for 6 weeks, and emphasizing activities of daily living. Subjects randomly assigned to the experimental condition also received 30-minute MP sessions provided directly after therapy requiring daily MP of the activities of daily living; subjects assigned to the control group received the same amount of therapist interaction as the experimental group, and a sham intervention directly after therapy, consisting of relaxation. Outcomes were evaluated by a blinded rater using the Action Research Arm test and the upper extremity section of the Fugl-Meyer Assessment.

RESULTS

No pre-existing group differences were found on any demographic variable or movement scale. Subjects receiving MP showed significant reductions in affected arm impairment and significant increases in daily arm function (both at the P<0.0001 level). Only patients in the group receiving MP exhibited new ability to perform valued activities.

CONCLUSIONS

The results support the efficacy of programs incorporating mental practice for rehabilitating affected arm motor function in patients with chronic stroke. These changes are clinically significant.

The Effects of Mental Practice in Stroke Rehabilitation: A Systematic Review

OBJECTIVE

To assess the effects of a mental practice intervention on recovery in stroke patients.

DATA SOURCES

A systematic literature search of the Cochrane Database of Systematic Reviews, PubMed/Medline, PsycINFO, Pedro, Rehadat, and RehabTrials was performed by 2 researchers independently. Eligible studies published through August 2005 were selected.

STUDY SELECTION

Four randomized controlled trials (RCTs), 1 controlled clinical trial (CCT), 2 patient series, and 3 case reports that investigated the effects of a mental practice intervention on recovery of stroke patients were included.

DATA EXTRACTION

The selected RCTs and CCT were assessed on a methodologic quality rating scale. Important characteristics and outcomes were extracted and summarized. Results and characteristics from the patient series and case reports were only provided if they added information.

DATA SYNTHESIS

Included studies differed clearly from one another with regard to patient characteristics, intervention protocol, and outcome measures. Four different mental practice strategies were used. Most tasks involved mentally rehearsing movements of the arm. Intervention periods varied from 2 to 6 weeks, frequencies ranged from multiple sessions per day to 3 times a week. Studies were limited in size. Power could not be increased by pooling or meta-analysis because studies were not comparable. Three of the 4 RCTs were of reasonable methodologic quality. There was some evidence that mental practice as an additional therapy intervention had positive effects on recovery of arm function after stroke. Two mental practice techniques appeared to be effective-tape instruction and self-regulation. Results from the single case studies indicate that mental practice is also promising for improvement of leg function.

CONCLUSIONS

No definite conclusions could be drawn except that further research, using clear definitions of the content of mental practice and standardized measurement of outcome, are needed.

Imagery-induced cortical excitability changes in stroke: a transcranial magnetic stimulation study

Focal transcranial magnetic stimulation (TMS) was employed in a population of hemiparetic stroke patients in a post-acute stage to map out the abductor digiti minimi (ADM) muscle cortical representation of the affected (AH) and unaffected (UH) hemisphere at rest, during motor imagery and during voluntary contraction. Imagery induced an enhancement of the ADM map area and volume in both hemispheres in a way which partly corrected the abnormal asymmetry between AH and UH motor output seen in rest condition. The voluntary contraction was the task provoking maximal facilitation in the UH, whereas a similar degree of facilitation was obtained during voluntary contraction and motor imagery in the AH. We argued that motor imagery could induce a pronounced motor output enhancement in the hemisphere affected by stroke. Further, we demonstrated that imagery-induced excitability changes were specific for the muscle 'prime mover' for the imagined movement, while no differences were observed with respect to the stroke lesion locations. Present findings demonstrated that motor imagery significantly enhanced the cortical excitability of the hemisphere affected by stroke in a post-acute stage. Further studies are needed to correlate these cortical excitability changes with short-term plasticity therefore prompting motor imagery as a 'cortical reservoir' in post-stroke motor rehabilitation.

Mental and physical practice schedules in acquisition and retention of novel timing skills

Research has indicated that random physical practice of a motor skill enhances effects of long-term learning more than blocked practice. Moreover, the use of mental rehearsal coupled with physical practice has been shown to accelerate motor skill acquisition in many different contexts and is better than no practice at all. Others have found that some mental rehearsal strategies are better than others for maximizing performance. This study examined how combinations of mental and physical practice schedules affected the learning of a coincidence timing task. 30 college students were randomly assigned to one of four treatment groups involving combinations of imagery and physical practice. Three tasks were utilized, each involving a particular speed (slow, medium, fast) on the Bassin Anticipation Timer. Conclusions were based on a three-way analysis of variance, using type of mental practice, type of physical practice, and sex as between-group factors, conducted separately for acquisition and retention trials. Type of physical practice was significantly related to performance. On the acquisition trials, random practice was associated with larger mean errors than blocked practice; however, the reverse was true for retention trials. There was no significant effect of type of mental practice in either the acquisition or retention phase. Sex was significantly related to performance for the retention trials only, where the 15 men made smaller errors than the 15 women.

The role of motor imagery in learning a totally novel movement

The aim of the present study is to gain more insight into the mechanisms underlying mental practice. The question of whether a totally novel movement may be learned by mental practice was investigated. Healthy young adults had to learn the abduction of the big toe (dominant right foot) without moving the other toes or the foot. The subjects were divided into two groups: subjects who were absolutely unable to abduct their big toe ("absolute zero" group) and subjects who were able to abduct their toe to some extent but showed clear room for improvement ("already doing it" group). Two separate experiments were executed. In the first experiment, 37 absolute-zero subjects had to practice, mentally or physically, the target movement. In the second experiment 40 already-doing-it subjects had to improve their toe-abduction skill. The results showed that absolute-zero subjects could not acquire the toe-abduction movement by means of mental practice. Only subjects who physically practiced the target movement improved significantly. Subjects who had some experience in the task (already-doing-it subjects) improved significantly after mental practice as well as after physical practice. The results seem to indicate that it is more plausible to explain the learning effects of mental practice in terms of a "top-down" mechanism based on the activation of a central representation of the movement than in terms of a peripheral "bottom-up" mechanism based on the activation of muscles.

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

Four experiments were undertaken to examine the effects of chronic hemiplegia on the ability to internally represent actions involving either the paralyzed (contralesional) or relatively unaffected (ipsilesional) limb. An experimental group of chronic, densely hemiplegic patients was compared with controls who experienced nearly full recovery from an initially dense hemiparesis. All participants suffered cerebral vascular accidents that spared sites in premotor and parietal areas directly involved in representing upper limb actions. Despite chronic limb immobility, hemiplegic patients performed all four tasks at a high level of accuracy and showed no differences in their ability to represent actions of the contralesional versus ipsilesional limbs. On tasks that involved representing actions of the hands and lower arms, hemiplegic patients were as accurate as recovered controls. Hemiplegic patients were, however, less accurate than controls on a task that involved representing actions of either upper arm. Overall, chronic hemiplegics performed more accurately for decisions based on their contralesional limbs: a "hemiplegic advantage" that may be related to an ongoing focus on planning and/or imagining currently impossible movements. These findings reveal a dissociation between the ability to internally "represent" versus "produce" manual actions. Further, they demonstrate that internal action representations can be robust to even years of limb disuse.

Mental practice effect on line-tracing accuracy in persons with hemiparetic stroke: a preliminary study

OBJECTIVE

To investigate the effect of mental practice on line-tracing accuracy of persons with hemiparetic stroke.

DESIGN

A single-case, experimental, multiple baseline design.

SETTING

Electromyography laboratory of a rehabilitation medicine department of a university hospital.

PARTICIPANTS

Three persons with right hemiparesis from stroke.

INTERVENTION

Mental practice for line-tracing training.

MAIN OUTCOMES MEASURES

Two tracing tasks were used to evaluate the effect of mental practice: (1) tracing a 5.9-inch long horizontal line (task 1); and (2) tracing a 6-inch long curved line (task 2) as a generalization probe. Participants were first trained to master the cognitive rehearsal skill by checking the reduction level of tension in their upper trapezius while listening to a relaxation cassette tape. Second, participants were trained to trace task 1 immediately after listening to a cognitive rehearsal tape that contained the command to trace over a horizontal line as accurately as possible. Then, without the cognitive rehearsal process, participants traced over a curved line as a generalization probe. The dependent variable, called the line length error, was the total distance that the traced line deviated from the printed lines (both horizontal and curved).

RESULTS

Mean-line length errors of participants 1, 2, and 3 were: horizontal line tracing, 3.33, 7.38, and.30 inches, respectively, in the baseline and 1.41, 2.70, and.24 inches, respectively, after mental practice training. With the curved line tracing, mean length errors were 3.15, 6.56, and.52 inches in the baseline and 1.85, 4.36, and.80 inches postintervention, respectively.

CONCLUSIONS

Mental practice can be an effective method to improve line tracing by persons with hemiparetic stroke. Training in horizontal line tracing showed a modest level of generalization to curved line tracing.

Mental practice combined with physical practice for upper-limb motor deficit in subacute stroke

BACKGROUND AND PURPOSE

This case report describes a patient with upper-limb hemiparesis (ULH) who received a program combining physical therapy for the affected side with mental practice.

CASE DESCRIPTION

The patient was a 56-year-old man with stable motor deficits, including ULH, on his dominant side resulting from a right parietal infarct that occurred 5 months previously. He received physical therapy for an hour 3 times a week for 6 weeks. In addition, 2 times a week the patient listened to an audiotape instructing him to imagine himself functionally using the affected limb. The patient also listened to the audiotape at home 2 times a week. Pretreatment and posttreatment measures were the upper-extremity scale of the Fugl-Meyer Assessment of Sensorimotor Impairment (Fugl-Meyer Scale), the Action Research Arm Test (ARA), and the Stroke Rehabilitation Assessment of Movement (STREAM).

OUTCOMES

The patient exhibited reduction in impairment (Fugl-Meyer Scale) and improvement in arm function, as measured by the ARA and STREAM.

DISCUSSION

Mental practice may complement physical therapy to improve motor function after stroke.

Mental effort-related EEG modulation during video-game play: comparison between juvenile subjects with epilepsy and normal control subjects

PURPOSE

This study investigated the effects of mental effort exerted during video-game play on features of the EEG in juvenile subjects diagnosed with seizure disorders and in age-matched clinically healthy subjects.

METHODS

EEG was recorded from 14 children (9-15 years old) as they played a video game, watched another person playing a video-game, and sat quietly with their eyes open. Seven of the subjects had been clinically diagnosed with seizure disorders, three of whom had also exhibited photosensitivity.

RESULTS

Three spectral components of the EEG showed cognitive load-related modulation. The amplitude of a frontal midline theta (6-7 Hz) signal increased with video-game play relative to the watching and eyes open resting conditions. A posterior alpha band (9-12 Hz) signal was attenuated during the playing and the watching conditions relative to the resting condition. A central mu (10-13 Hz) rhythm was attenuated during the game-playing condition. No significant differences were found between the patient and control groups for any of these features. Incidence of epileptiform events did not discriminate test conditions in the children with epilepsy.

CONCLUSIONS

The results from this small sample suggest that video-game play tends to produce similar responses from children with epilepsy and in healthy control subjects. These responses in the juvenile population are similar to responses elicited by increased mental load in normal adult populations.

Neurophysiological indices of strategy development and skill acquisition

In order to examine neurophysiological changes associated with the development of cognitive and visuomotor strategies and skills, spectral features of the EEG were measured as participants learned to perform new tasks. In one experiment eight individuals practiced working memory tasks that required development of either spatial or verbal rehearsal and updating strategies. In a second experiment six individuals practiced a video game with a difficult visuomotor tracking component. The alpha rhythm, which is attenuated by functional cortical activation, was affected by task practice. In both experiments, a lower-frequency, centrally distributed alpha component increased between practice sessions in a task-independent fashion, reflecting an overall decrease in the extent of cortical activation after practice. A second, higher-frequency, posterior component of the alpha rhythm displayed task-specific practice effects. Practice in the verbal working memory task resulted in an increase of this signal over right posterior regions, an effect not seen after practice with the spatial working memory task or with the video game. This between-task difference presumably reflects a continued involvement of the posterior region of the right hemisphere in tasks that invoke visuospatial processes. This finding thus provides neurophysiological evidence for the formation of a task-specific neurocognitive strategy. In the second experiment a third component of the alpha rhythm, localized over somatomotor cortex, was enhanced in conjunction with acquisition of tracking skill. These alpha band results suggest that cortical regions not necessary for task performance become less active as skills develop. In both experiments the frontal midline (Fm) theta rhythm also displayed increases over the course of test sessions. This signal is associated with states of focused concentration, and its enhancement might reflect the conscious control over attention associated with maintenance of a task-appropriate mental set. Overall, the results suggest that the EEG can be used to monitor practice-related changes in the patterns of cortical activity that are associated with task processing. Additionally, these results highlight the importance of ensuring that subjects have developed stable strategies for performance before drawing inferences about the functional architecture underlying specific cognitive processes.

Theta power decreases in preparation for voluntary isometric contractions performed with maximal subjective effort

In order to find EEG parameters that can be attributed to movements performed with maximal subjective effort, EEG recordings and force measurements were realized in connection with isometric contractions (IMC). IMC were performed with submaximal and maximal subjective effort. Mean spectral power density within the theta band was found as an indicator for maximal subjective effort. The theta power across the parieto-occipital area decreases from rest through movements performed with submaximal force to movements performed with maximal effort. It is argued that this theta decrease possibly reflects a down-regulation of the posterior attention system in order to minimize the influences of external stimuli during the preparation for voluntary IMC performed with maximal subjective effort.