Motor imagery: perception or action?

Motor imagery of body movements that can't be executed on Earth

BACKGROUND

Before participating in a space mission, astronauts undergo parabolic-flight and underwater training to facilitate their subsequent adaptation to weightlessness. A quick, simple and inexpensive alternative could be training by motor imagery (MI).

OBJECTIVE

An important prerequisite for this training approach is that humans are able to imagine movements which are unfamiliar, since they can't be performed in the presence of gravity. Our study addresses this prerequisite.

METHODS

68 young subjects completed a modified version of the CMI test (Schott, 2013). With eyes closed, subjects were asked to imagine moving their body according to six consecutive verbal instructions. After the sixth instruction, subjects opened their eyes and arranged the segments of a manikin into the assumed final body configuration. In a first condition, subjects received instructions only for moving individual body segments (CMIground). In a second condition, subjects received instructions for moving body segments or their full body (CMIfloat). After each condition, subjects were asked to rate their subjective visual and kinesthetic vividness of MI.

RESULTS

Condition differences emerged for the CMI scores and for the duration of correct trials with better performance in the CMIground condition. Condition differences were also represented for the subjective MI performance.

CONCLUSION

Motor imagery is possible but degraded when subjects are asked to imagine body movements while floating. This confirms that preflight training of MI while floating might be beneficial for astronauts' mission performance.

Motor imagery-based skill acquisition disrupted following rTMS of the inferior parietal lobule

Motor imagery (MI), the mental rehearsal of motor tasks, has promise as a therapy in post-stroke rehabilitation. The potential effectiveness of MI is attributed to the facilitation of plasticity in numerous brain regions akin to those recruited for physical practice. It is suggested, however, that MI relies more heavily on regions commonly affected post-stroke, including left hemisphere parietal regions involved in visuospatial processes. However, the impact of parietal damage on MI-based skill acquisition that underlies rehabilitation remains unclear. Here, we examine the contribution of the left inferior parietal lobule (IPL) to MI using inhibitory transcranial magnetic stimulation (TMS) and an MI-based implicit sequence learning (ISL) paradigm. Participants (N = 27) completed the MI-based ISL paradigm after receiving continuous theta burst stimulation to the left IPL (TMS), or with the coil angled away from the scalp (sham). Reaction time differences (dRT) and effect sizes between implicit and random sequences assessed success of MI-based learning. Mean dRT for the sham group was 36.1 ± 28.2 ms (d = 0.71). Mean dRT in the TMS group was 7.7 ± 38.5 ms (d = 0.11). These results indicate that inhibition of the left IPL impaired MI-based learning. We conclude that the IPL and likely the visuospatial processes it mediates are critical for MI performance and thus MI-based skill acquisition or learning. Ultimately, these findings have implications for the use of MI in post-stroke rehabilitation.

The Importance of Visual Feedback Design in BCIs; from Embodiment to Motor Imagery Learning

Brain computer interfaces (BCIs) have been developed and implemented in many areas as a new communication channel between the human brain and external devices. Despite their rapid growth and broad popularity, the inaccurate performance and cost of user-training are yet the main issues that prevent their application out of the research and clinical environment. We previously introduced a BCI system for the control of a very humanlike android that could raise a sense of embodiment and agency in the operators only by imagining a movement (motor imagery) and watching the robot perform it. Also using the same setup, we further discovered that the positive bias of subjects' performance both increased their sensation of embodiment and improved their motor imagery skills in a short period. In this work, we studied the shared mechanism between the experience of embodiment and motor imagery. We compared the trend of motor imagery learning when two groups of subjects BCI-operated different looking robots, a very humanlike android's hands and a pair of metallic gripper. Although our experiments did not show a significant change of learning between the two groups immediately during one session, the android group revealed better motor imagery skills in the follow up session when both groups repeated the task using the non-humanlike gripper. This result shows that motor imagery skills learnt during the BCI-operation of humanlike hands are more robust to time and visual feedback changes. We discuss the role of embodiment and mirror neuron system in such outcome and propose the application of androids for efficient BCI training.

Can You Imagine? The Effect of Mental Practice on the Acquisition and Retention of a Motor Skill as a Function of Age

The differences among participants of various ages in their ability to use mental practice for motor skill acquisition have not been examined to date. The purpose of this study was to investigate the effect of age on mental practice. Participants were divided into 3 age groups: children, adults, and older adults; each group was randomly subdivided into physical and mental-physical practice groups. The results indicated that mental practice affected the 3 age groups differently. Mental practice in the acquisition phase of bimanual coordination task was found to be beneficial for children and older adults only. In the retention phase, this benefit was confined to older adults. Adults in the mental-physical and physical practice groups did not differ in performance of the acquired task. These findings indicate that at both ends of our lives—in childhood and old age—we benefit more from mental practice. Mental practice was especially beneficial for older adults regarding their retention process.

Motor and mental training in older people: Transfer, interference, and associated functional neural responses

Learning new motor skills may become more difficult with advanced age. In the present study, we randomized 56 older individuals, including 30 women (mean age 70.6 years), to 6 weeks of motor training, mental (motor imagery) training, or a combination of motor and mental training of a finger tapping sequence. Performance improvements and post-training functional magnetic resonance imaging (fMRI) were used to investigate performance gains and associated underlying neural processes. Motor-only training and a combination of motor and mental training improved performance in the trained task more than mental-only training. The fMRI data showed that motor training was associated with a representation in the premotor cortex and mental training with a representation in the secondary visual cortex. Combining motor and mental training resulted in both premotor and visual cortex representations. During fMRI scanning, reduced performance was observed in the combined motor and mental training group, possibly indicating interference between the two training methods. We concluded that motor and motor imagery training in older individuals is associated with different functional brain responses. Furthermore, adding mental training to motor training did not result in additional performance gains compared to motor-only training and combining training methods may result in interference between representations, reducing performance.

Electroencephalographic Motor Imagery Brain Connectivity Analysis for BCI: A Review

Recent research has reached a consensus on the feasibility of motor imagery brain-computer interface (MI-BCI) for different applications, especially in stroke rehabilitation. Most MI-BCI systems rely on temporal, spectral, and spatial features of single channels to distinguish different MI patterns. However, no successful communication has been established for a completely locked-in subject. To provide more useful and informative features, it has been recommended to take into account the relationships among electroencephalographic (EEG) sensor/source signals in the form of brain connectivity as an efficient tool of neuroscience. In this review, we briefly report the challenges and limitations of conventional MI-BCIs. Brain connectivity analysis, particularly functional and effective, has been described as one of the most promising approaches for improving MI-BCI performance. An extensive literature on EEG-based MI brain connectivity analysis of healthy subjects is reviewed. We subsequently discuss the brain connectomes during left and right hand, feet, and tongue MI movements. Moreover, key components involved in brain connectivity analysis that considerably affect the results are explained. Finally, possible technical shortcomings that may have influenced the results in previous research are addressed and suggestions are provided.

Tracking Plasticity: Effects of Long-Term Rehearsal in Expert Dancers Encoding Music to Movement

Our knowledge of neural plasticity suggests that neural networks show adaptation to environmental and intrinsic change. In particular, studies investigating the neuroplastic changes associated with learning and practicing motor tasks have shown that practicing such tasks results in an increase in neural activation in several specific brain regions. However, studies comparing experts and non-experts suggest that experts employ less neuronal activation than non-experts when performing a familiar motor task. Here, we aimed to determine the long-term changes in neural networks associated with learning a new dance in professional ballet dancers over 34 weeks. Subjects visualized dance movements to music while undergoing fMRI scanning at four time points over 34-weeks. Results demonstrated that initial learning and performance at seven weeks led to increases in activation in cortical regions during visualization compared to the first week. However, at 34 weeks, the cortical networks showed reduced activation compared to week seven. Specifically, motor learning and performance over the 34 weeks showed the typical inverted-U-shaped function of learning. Further, our result demonstrate that learning of a motor sequence of dance movements to music in the real world can be visualized by expert dancers using fMRI and capture highly significant modeled fits of the brain network variance of BOLD signals from early learning to expert level performance.

An online three-class Transcranial Doppler ultrasound brain computer interface

Brain computer interfaces (BCI) can provide communication opportunities for individuals with severe motor disabilities. Transcranial Doppler ultrasound (TCD) measures cerebral blood flow velocities and can be used to develop a BCI. A previously implemented TCD BCI system used verbal and spatial tasks as control signals; however, the spatial task involved a visual cue that awkwardly diverted the user's attention away from the communication interface. Therefore, vision-independent right-lateralized tasks were investigated. Using a bilateral TCD BCI, ten participants controlled online, an on-screen keyboard using a left-lateralized task (verbal fluency), a right-lateralized task (fist motor imagery or 3D-shape tracing), and unconstrained rest. 3D-shape tracing was generally more discernible from other tasks than was fist motor imagery. Verbal fluency, 3D-shape tracing and unconstrained rest were distinguished from each other using a linear discriminant classifier, achieving a mean agreement of κ=0.43±0.17. These rates are comparable to the best offline three-class TCD BCI accuracies reported thus far. The online communication system achieved a mean information transfer rate (ITR) of 1.08±0.69bits/min with values reaching up to 2.46bits/min, thereby exceeding the ITR of previous online TCD BCIs. These findings demonstrate the potential of a three-class online TCD BCI that does not require visual task cues.

Short-term kinesthetic training for sensorimotor rhythms: effects in experts and amateurs

The authors' aim was to examine whether short-term kinesthetic training affects the level of sensorimotor rhythm (SMR) in different frequency band: alpha (8-12 Hz), lower beta (12.5-16 Hz) and beta (16.5-20 Hz) during the execution of a motor imagery task of closing and opening the right and the left hand by experts (jugglers, practicing similar exercises on an everyday basis) and amateurs (individuals not practicing any sports). It was found that the performance of short kinesthetic training increases the power of alpha rhythm when executing imagery tasks only in the group of amateurs. Therefore, kinesthetic training may be successfully used as a method increasing the vividness of motor imagery, for example, in tasks involving the control of brain-computer interfaces based on SMR.

Interference from mere thinking: mental rehearsal temporarily disrupts recall of motor memory

Interference between successively learned tasks is widely investigated to study motor memory. However, how simultaneously learned motor memories interact with each other has been rarely studied despite its prevalence in daily life. Assuming that motor memory shares common neural mechanisms with declarative memory system, we made unintuitive predictions that mental rehearsal, as opposed to further practice, of one motor memory will temporarily impair the recall of another simultaneously learned memory. Subjects simultaneously learned two sensorimotor tasks, i.e., visuomotor rotation and gain. They retrieved one memory by either practice or mental rehearsal and then had their memory evaluated. We found that mental rehearsal, instead of execution, impaired the recall of unretrieved memory. This impairment was content-independent, i.e., retrieving either gain or rotation impaired the other memory. Hence, conscious recollection of one motor memory interferes with the recall of another memory. This is analogous to retrieval-induced forgetting in declarative memory, suggesting a common neural process across memory systems. Our findings indicate that motor imagery is sufficient to induce interference between motor memories. Mental rehearsal, currently widely regarded as beneficial for motor performance, negatively affects memory recall when it is exercised for a subset of memorized items.

Implementation of specific motor expertise during a mental rotation task of hands

Mental rotation of the hands classically induces kinesthetic effects according to the direction of the rotation, with faster response times to the hands' medial rotations compared with lateral rotations, and is thus commonly used to induce engagement in motor imagery (MI). In the present study, we compared the performances of table tennis players (experts on hand movements), who commonly execute and observe fast hand movements, to those of soccer players (non-experts on hand movements) on a mental rotation task of hands. Our results showed a significant effect of the direction of rotation (DOR) confirming the engagement of the participants in MI. In addition, only hand movement experts were faster when the task figures corresponded to their dominant hand compared with the non-dominant hand, revealing a selective effect of motor expertise. Interestingly, the effect of the DOR collapsed in hand movement experts only when the task figures corresponded to their dominant hand, but it is noteworthy that lateral and medial rotations of the right-hand stimuli were not faster than medial rotations of the left-hand stimuli. These results are discussed in relation to possible strategies during the task. Overall, the present study highlights the embodied nature of the mental rotation task of hands by revealing selective effects of motor expertise.

Mental representation and mental practice: experimental investigation on the functional links between motor memory and motor imagery

Recent research on mental representation of complex action has revealed distinct differences in the structure of representational frameworks between experts and novices. More recently, research on the development of mental representation structure has elicited functional changes in novices' representations as a result of practice. However, research investigating if and how mental practice adds to this adaptation process is lacking. In the present study, we examined the influence of mental practice (i.e., motor imagery rehearsal) on both putting performance and the development of one's representation of the golf putt during early skill acquisition. Novice golfers (N = 52) practiced the task of golf putting under one of four different practice conditions: mental, physical, mental-physical combined, and no practice. Participants were tested prior to and after a practice phase, as well as after a three day retention interval. Mental representation structures of the putt were measured, using the structural dimensional analysis of mental representation. This method provides psychometric data on the distances and groupings of basic action concepts in long-term memory. Additionally, putting accuracy and putting consistency were measured using two-dimensional error scores of each putt. Findings revealed significant performance improvements over the course of practice together with functional adaptations in mental representation structure. Interestingly, after three days of practice, the mental representations of participants who incorporated mental practice into their practice regime displayed representation structures that were more similar to a functional structure than did participants who did not incorporate mental practice. The findings of the present study suggest that mental practice promotes the cognitive adaptation process during motor learning, leading to more elaborate representations than physical practice only.

Cortical Mechanisms Underlying the Organization of Goal-Directed Actions and Mirror Neuron-Based Action Understanding

Our understanding of the functions of motor system evolved remarkably in the last 20 years. This is the consequence not only of an increase in the amount of data on this system but especially of a paradigm shift in our conceptualization of it. Motor system is not considered anymore just a “producer” of movements, as it was in the past, but a system crucially involved in cognitive functions. In the present study we review the data on the cortical organization underlying goal-directed actions and action understanding. Our review is subdivided into two major parts. In the first part, we review the anatomical and functional organization of the premotor and parietal areas of monkeys and humans. We show that the parietal and frontal areas form circuits devoted to specific motor functions. We discuss, in particular, the visuo-motor transformation necessary for reaching and for grasping. In the second part we show how a specific neural mechanism, the mirror mechanism, is involved in understanding the action and intention of others. This mechanism is located in the same parieto-frontal circuits that mediate goal-directed actions. We conclude by indicating future directions for studies on the mirror mechanism and suggest some major topics for forthcoming research.

Effect of imagery perspective on occupational performance after stroke: a randomized controlled trial

OBJECTIVE

This preliminary study sought to determine whether the imagery perspective used during mental practice (MP) differentially influenced performance outcomes after stroke.

METHOD

Nineteen participants with unilateral subacute stroke (9 men and 10 women, ages 28-77) were randomly allocated to one of three groups. All groups received 30-min occupational therapy sessions 2×/wk for 6 wk. Experimental groups received MP training in functional tasks using either an internal or an external perspective; the control group received relaxation imagery training. Participants were pre- and posttested using the Fugl-Meyer Motor Assessment (FMA), the Jebsen-Taylor Test of Hand Function (JTTHF), and the Canadian Occupational Performance Measure (COPM).

RESULTS

At posttest, the internal and external experimental groups showed statistically similar improvements on the FMA and JTTHF (p < .05). All groups improved on the COPM (p < .05).

CONCLUSION

MP combined with occupational therapy improves upper-extremity recovery after stroke. MP does not appear to enhance self-perception of performance. This preliminary study suggests that imagery perspective may not be an important variable in MP interventions.

Cortical lateralization in stroke patients measured by event‑related potentials during motor imagery

Stroke is a leading cause of impairment and disability worldwide, and motor imagery (MI) has been used in stroke rehabilitation. Electroencephalography (EEG) has been used to study MI. However, the characteristic features of EEG during MI in stroke patients have not been established. The purpose of this study was to investigate the difference in event‑related potentials (ERPs) during MI between healthy controls and stroke patients. This study included nine stroke patients and nine healthy age‑matched controls, who performed tasks involving MI, passive movement without MI and passive movement with MI. One hundred and twenty‑eight channel ERPs were recorded to capture cerebral activation. Electrodes E44 and E120 (corresponding to the inferior precentral area) were selected to analyze the lateralization effects of ERPs. Lateralization was calculated as the ratio of the potential at 500 ms at electrode E120 to that at electrode E44. In the controls, the different ERPs exhibited differential direction between the 0‑300 and the 300‑700 ms interval. ERPs were evoked by passive movement with MI and MI alone, but not passive movement without MI. In addition, a lateralization effect in control patients as shown by the observation that the lateralization ratio in passive movement with MI and MI alone was significantly different from that in passive movement without MI (P<0.05). The amplitudes of the different ERPs were significantly smaller in stroke patients compared with those in the controls (P<0.05). The lateralization ratio in the stroke patients was opposite and significantly different from that of the controls (P<0.05). The results suggested that the MI‑induced lateralization effect in ERPs may be used as a measure for evaluating the MI impairment and recovery in stroke patients.

Effects of hand orientation on motor imagery--event related potentials suggest kinesthetic motor imagery to solve the hand laterality judgment task

Motor imagery (MI) refers to the process of imagining the execution of a specific motor action without actually producing an overt movement. Two forms of MI have been distinguished: visual MI and kinesthetic MI. To distinguish between these forms of MI we employed an event related potential (ERP) study to measure interference effects induced by hand orientation manipulations in a hand laterality judgement task. We hypothesized that this manipulation should only affect kinesthetic MI but not visual MI. The ERPs elicited by rotated hand stimuli contained the classic rotation related negativity (RRN) with respect to palm view stimuli. We observed that laterally rotated stimuli led to a more marked RRN than medially rotated stimuli. This RRN effect was observed when participants had their hands positioned in either a straight (control) or an inward rotated posture, but not when their hands were positioned in an outward rotated posture. Posture effects on the ERP-RRN have not previously been studied. Apparently, a congruent hand posture (hands positioned in an outward rotated fashion) facilitates the judgement of the otherwise more demanding laterally rotated hand stimuli. These ERP findings support a kinesthetic interpretation of MI involved in solving the hand laterality judgement task. The RRN may be used as a non-invasive marker for kinesthetic MI and seems useful in revealing the covert behavior of MI in e.g. rehabilitation programs.

Action simulation in hallucination-prone adolescents

Theoretical and empirical accounts suggest that impairments in self-other discrimination processes are likely to promote the expression of hallucinations. Studies using a variety of paradigms involving self-performed actions argue in favor of perspective taking confusion in hallucination-prone subjects. However, our understanding of such processes during adolescence is still at an early stage. The present study thus aims (1) to delineate the neural correlates sustaining mental simulation of actions involving self-performed actions (first-person perspective; 1PP) and other-performed actions (third-person perspective; 3PP) during adolescence (2) to identify atypical activation patterns during 1PP/3PP mental simulation of actions in hallucination-prone adolescents (3) to examine whether differential risk for schizophrenia (clinical vs. genetic) is also associated with differential impairments in the 1PP/3PP mental simulation of actions during adolescence. Twenty-two typically developing controls (Control group; 6 females), 12 hallucination-prone adolescents [auditory hallucination (AH) group; 7 females] and 13 adolescents with 22q11.2 Deletion Syndrome (22q11.2DS group; 4 females) were included in the study. During the fMRI task, subjects were presented with a cue (self-other priming cues) indicating to perform the task using either a first person perspective (“you”-1PP) or a third person perspective (“best friend”-3PP) and then they were asked to mentally simulate actions based on the type of cue. Hallucination-proneness was assessed using a self-report questionnaire [Cardiff Anomalous Perception Scale (CAPS)]. Our results indicated that atypical patterns of cerebral activation, particularly in the key areas of self-other distinction, were found in both groups at risk for auditory hallucinations (AHs and 22q11.2DS). More precisely, adolescents in the AH group presented decreased activations in the right middle occipital gyrus BA19, left cingulate gyrus BA31, and right precuneus BA31 for the 3PP > 1PP contrast. Adolescents in the 22q11.2DS group presented decreased activations in the right superior occipital gyrus BA19, left caudate tail and left precuneus BA7 for the 3PP > 1PP contrast. In comparison to the Control group, only the 22q11.2DS adolescents showed a decreased activation for other-related cues (prime other > prime self contrast) in areas of visual imagery, episodic memory and social cognition. This study characterizes the neural correlates of mental imagery for actions during adolescence, and suggests that a differential risk for hallucination-proneness (clinical vs. genetic) is associated to similar patterns of atypical activations in key areas sustaining self-other discrimination processes. These observations may provide relevant information for future research and prevention strategies with regards to hallucination-proneness during adolescence.

Multimodal functional imaging of motor imagery using a novel paradigm

Neuroimaging studies have shown that the neural mechanisms of motor imagery (MI) overlap substantially with the mechanisms of motor execution (ME). Surprisingly, however, the role of several regions of the motor circuitry in MI remains controversial, a variability that may be due to differences in neuroimaging techniques, MI training, instruction types, or tasks used to evoke MI. The objectives of this study were twofold: (i) to design a novel task that reliably invokes MI, provides a reliable behavioral measure of MI performance, and is transferable across imaging modalities; and (ii) to measure the common and differential activations for MI and ME with functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG). We present a task in which it is difficult to give accurate responses without the use of either motor execution or motor imagery. The behavioral results demonstrate that participants performed similarly on the task when they imagined vs. executed movements and this performance did not change over time. The fMRI results show a spatial overlap of MI and ME in a number of motor and premotor areas, sensory cortices, cerebellum, inferior frontal gyrus, and ventrolateral thalamus. MI uniquely engaged bilateral occipital areas, left parahippocampus, and other temporal and frontal areas, whereas ME yielded unique activity in motor and sensory areas, cerebellum, precuneus, and putamen. The MEG results show a robust event-related beta band desynchronization in the proximity of primary motor and premotor cortices during both ME and MI. Together, these results further elucidate the neural circuitry of MI and show that our task robustly and reliably invokes motor imagery, and thus may prove useful for interrogating the functional status of the motor circuitry in patients with motor disorders.

The relation between cognitive and motor dysfunction and motor imagery ability in patients with multiple sclerosis

Background:

Motor imagery (MI) was recently shown to be a promising tool in neurorehabilitation. The ability to perform MI, however, may be impaired in some patients with neurological dysfunction.

Objective:

The objective was to assess the relation between cognitive and motor dysfunction and MI ability in patients with multiple sclerosis (MS).

Methods:

Thirty patients with MS underwent cognitive and motor screening, and also performed a composite test battery to assess their MI ability. This test battery consisted of a questionnaire, a hand rotation task and a test based on mental chronometry. Patients’ MI ability was compared with the MI ability of age-matched healthy controls. Moreover, their MI scores were compared between body sides and were correlated with their scores on tests of motor and cognitive functioning.

Results:

The average accuracy and temporal organization of MI significantly differed between MS patients and controls. Patients’ MI accuracy significantly correlated with impairments in cognitive functioning, but was independent of motor functioning. MI duration, on the other hand, was independent of cognitive performance, but differed between the patients’ most and least affected side.

Conclusion:

These findings are of use when considering the application of MI practice in MS patients’ rehabilitation.

Sequential vs simultaneous encoding of spatial information: a comparison between the blind and the sighted

The aim of this research is to assess whether the crucial factor in determining the characteristics of blind people's spatial mental images is concerned with the visual impairment per se or the processing style that the dominant perceptual modalities used to acquire spatial information impose, i.e. simultaneous (vision) vs sequential (kinaesthesis). Participants were asked to learn six positions in a large parking area via movement alone (congenitally blind, adventitiously blind, blindfolded sighted) or with vision plus movement (simultaneous sighted, sequential sighted), and then to mentally scan between positions in the path. The crucial manipulation concerned the sequential sighted group. Their visual exploration was made sequential by putting visual obstacles within the pathway in such a way that they could not see simultaneously the positions along the pathway. The results revealed a significant time/distance linear relation in all tested groups. However, the linear component was lower in sequential sighted and blind participants, especially congenital. Sequential sighted and congenitally blind participants showed an almost overlapping performance. Differences between groups became evident when mentally scanning farther distances (more than 5m). This threshold effect could be revealing of processing limitations due to the need of integrating and updating spatial information. Overall, the results suggest that the characteristics of the processing style rather than the visual impairment per se affect blind people's spatial mental images.

The action-sentence compatibility effect in Japanese sentences

The action-sentence compatibility effect (ACE) is a phenomenon in which a reader's response to a sentence is made faster when there is congruity between the action described in the sentence and the action that makes up the response. Previous studies showed the ACE occurs in action-related sentences in several languages. However, all these were SVO (verb-object) languages, in which verbs are placed before object nouns; this order is reversed in SOV languages. Moreover, those studies investigated hand responses. This study assessed the existence of the ACE in Japanese, an SOV language, and in foot responses. 24 female participants judged the sensibility of Japanese sentences that described actions and responded with either their foot or hand as an effector. Reaction times were significantly faster when there was congruity between the effector described in the sentences and the effector actually used for the response. However, sentence dependency was also found in the foot responses.

Physical fidelity versus cognitive fidelity training in procedural skills acquisition

OBJECTIVE

The current study examined whether training simulators for the acquisition of procedural skills should emphasize physical fidelity or cognitive fidelity of the task.

BACKGROUND

Simulation-based training for acquiring and practicing procedural skills is becoming widely established. Generally speaking, these simulators offer technological sophistication but disregard theory-based design, leaving unanswered the question of what task features should be represented in the simulators.The authors compared real-world training and two alternative virtual trainers, one emphasizing physical fidelity and the other cognitive fidelity of the task.

METHOD

Participants were randomly assigned to one of four training groups in a LEGO assembly task: virtual-physical fidelity, cognitive fidelity, real world, and control. A posttraining test to assess the development of procedural skills was conducted.

RESULTS

Both the virtual-physical fidelity and cognitive fidelity training methods produced better performance time than no training at all, as did the real-world training. The cognitive fidelity training was inferior in terms of test time compared to the real-world training, whereas the virtual-physical fidelity training was not. In contrast, only the real-world and the cognitive fidelity groups, and not the virtual-physical fidelity group, required significantly less time than the control group for error correction.

CONCLUSION

The two training methods have complementary advantages.

APPLICATION

Combining physical fidelity and cognitive training methods can enhance procedural skills acquisition when real-world training is not practicable.

Strength gains by motor imagery with different ratios of physical to mental practice

The purpose of this training study was to determine the magnitude of strength gains following a high-intensity resistance training (i.e., improvement of neuromuscular coordination) that can be achieved by imagery of the respective muscle contraction imagined maximal isometric contraction (IMC training). Prior to the experimental intervention, subjects completed a 4-week standardized strength training program. 3 groups with different combinations of real maximum voluntary contraction (MVC) and mental (IMC) strength training (M75, M50, M25; numbers indicate percentages of mental trials) were compared to a MVC-only training group (M0) and a control condition without strength training (CO). Training sessions (altogether 12) consisted of four sets of two maximal 5-s isometric contractions with 10 s rest between sets of either MVC or IMC training. Task-specific effects of IMC training were tested in four strength exercises commonly used in practical settings (bench pressing, leg pressing, triceps extension, and calf raising). Maximum isometric voluntary contraction force (MVC) was measured before and after the experimental training intervention and again 1 week after cessation of the program. IMC groups (M25, M50, M75) showed slightly smaller increases in MVC (3.0% to 4.2%) than M0 (5.1%), but significantly stronger improvements than CO (−0.2%). Compared to further strength gains in M0 after 1 week (9.4% altogether), IMC groups showed no “delayed” improvement, but the attained training effects remained stable. It is concluded that high-intensity strength training sessions can be partly replaced by IMC training sessions without any considerable reduction of strength gains.

Best practice for motor imagery: a systematic literature review on motor imagery training elements in five different disciplines

BACKGROUND

The literature suggests a beneficial effect of motor imagery (MI) if combined with physical practice, but detailed descriptions of MI training session (MITS) elements and temporal parameters are lacking. The aim of this review was to identify the characteristics of a successful MITS and compare these for different disciplines, MI session types, task focus, age, gender and MI modification during intervention.

METHODS

An extended systematic literature search using 24 databases was performed for five disciplines: Education, Medicine, Music, Psychology and Sports. References that described an MI intervention that focused on motor skills, performance or strength improvement were included. Information describing 17 MITS elements was extracted based on the PETTLEP (physical, environment, timing, task, learning, emotion, perspective) approach. Seven elements describing the MITS temporal parameters were calculated: study duration, intervention duration, MITS duration, total MITS count, MITS per week, MI trials per MITS and total MI training time.

RESULTS

Both independent reviewers found 96% congruity, which was tested on a random sample of 20% of all references. After selection, 133 studies reporting 141 MI interventions were included. The locations of the MITS and position of the participants during MI were task-specific. Participants received acoustic detailed MI instructions, which were mostly standardised and live. During MI practice, participants kept their eyes closed. MI training was performed from an internal perspective with a kinaesthetic mode. Changes in MI content, duration and dosage were reported in 31 MI interventions. Familiarisation sessions before the start of the MI intervention were mentioned in 17 reports. MI interventions focused with decreasing relevance on motor-, cognitive- and strength-focused tasks. Average study intervention lasted 34 days, with participants practicing MI on average three times per week for 17 minutes, with 34 MI trials. Average total MI time was 178 minutes including 13 MITS. Reporting rate varied between 25.5% and 95.5%.

CONCLUSIONS

MITS elements of successful interventions were individual, supervised and non-directed sessions, added after physical practice. Successful design characteristics were dominant in the Psychology literature, in interventions focusing on motor and strength-related tasks, in interventions with participants aged 20 to 29 years old, and in MI interventions including participants of both genders. Systematic searching of the MI literature was constrained by the lack of a defined MeSH term.

Mental practice with motor imagery in stroke recovery: randomized controlled trial of efficacy

This randomized controlled trial evaluated the therapeutic benefit of mental practice with motor imagery in stroke patients with persistent upper limb motor weakness. There is evidence to suggest that mental rehearsal of movement can produce effects normally attributed to practising the actual movements. Imagining hand movements could stimulate restitution and redistribution of brain activity, which accompanies recovery of hand function, thus resulting in a reduced motor deficit. Current efficacy evidence for mental practice with motor imagery in stroke is insufficient due to methodological limitations. This randomized controlled sequential cohort study included 121 stroke patients with a residual upper limb weakness within 6 months following stroke (on average <3 months post-stroke). Randomization was performed using an automated statistical minimizing procedure. The primary outcome measure was a blinded rating on the Action Research Arm test. The study analysed the outcome of 39 patients involved in 4 weeks of mental rehearsal of upper limb movements during 45-min supervised sessions three times a week and structured independent sessions twice a week, compared to 31 patients who performed equally intensive non-motor mental rehearsal, and 32 patients receiving normal care without additional training. No differences between the treatment groups were found at baseline or outcome on the Action Research Arm Test (ANCOVA statistical P=0.77, and effect size partial η2=0.005) or any of the secondary outcome measures. Results suggest that mental practice with motor imagery does not enhance motor recovery in patients early post-stroke. In light of the evidence, it remains to be seen whether mental practice with motor imagery is a valid rehabilitation technique in its own right.

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

OBJECTIVE

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

METHOD

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

RESULTS

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

CONCLUSION

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

The role of visual experience in mental scanning of actual pathways: evidence from blind and sighted people

In this research we compare blind and normally sighted people in mental scanning of spatial maps using locomotor or visual/locomotor exploration of a real 3-D environment. Different types of visual experience were tested: early (congenital) and late (adventitious) onset of blindness, short-term deprivation (blindfolded-sighted), and full vision (sighted). Participants were asked to learn six positions in a large parking area with movement alone (congenital, adventitious, blindfolded-sighted) or with vision plus movement (sighted), and then to mentally scan between positions in the path. Finally, they had to describe how they imagined scanning the learned pathway. We found a significant linear relation between space and time, ie the classic mental scanning effect, in all tested groups. However, the linear component was lower in blind participants, especially congenital. Instead, short-term visual deprivation had minimal impact on mental scanning. Overall, blind participants had shorter scanning times than both sighted groups, and the effect was particularly evident with farther distances. These results suggest that there is a quantitative rather than a qualitative difference between the blind and the sighted. In addition, the mental scanning strategies reported by participants also affected mental scanning times. The theoretical implications of these findings are discussed.

Brain oscillatory activity during motor imagery in EEG-fMRI coregistration

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

Perceptual integration of illusory and imagined kinesthetic images

It is generally agreed that motor imagery involves kinesthetic sensations especially as far as first-person imagery is concerned. It was proposed to determine the extent to which motor imagery and vibration-induced illusory sensations of movement are integrated perceptually. Imagined and illusory hand movements were evoked both separately and in various combinations in 12 volunteers. After each trial, the participants were asked to draw the movement trajectory perceived. In all the subjects, propriomimetic vibration patterns applied to various wrist muscles induced spatially oriented or more complex illusory hand movements such as writing or drawing. Depending on the instructions, the subjects were also able to produce imagined hand movements in various directions and at two different velocities. When straight illusory and imagined movements were evoked simultaneously, all the subjects perceived a single movement trajectory, in which the direction and the velocity of the two ongoing sensations were exactly integrated. This perceptual integration also occurred in the case of more complex movements, such as writing and drawing, giving rise to the perception of original trajectories also combining the features of both motor images. Because these two kinesthetic images, the one intentionally and centrally induced and the other peripherally evoked, activate almost the same neural network including cortical sensory and motor areas, parietal regions, and the cerebellum, these results suggest that common processes may be involved in such a perceptual fusion. The nature of these common processes is discussed, and some fields of research in which these findings could potentially be applied are suggested.