Measuring motor imagery ability: A review

Evaluating Motor Imagery Capabilities in Fatigued Versus Non-Fatigued Individuals With Multiple Sclerosis Without Cognitive Impairment

BackgroundMotor imagery is adversely affected by various factors in individuals with multiple sclerosis (MS). However, the impact of MS-related fatigue on motor imagery remains unclear. Our study aimed to compare motor imagery abilities between fatigued and non-fatigued individuals with MS without cognitive impairment.MethodsThis study included 73 individuals with MS, with Expanded Disability Status Scale scores from 0 to 4.5. Participants were divided into 2 groups based on Fatigue Severity Scale scores: ≥4 for Fatigued Group and <4 for Non-fatigued Group. Assessment of motor imagery vividness was done through Kinesthetic and Visual Imagery Questionnaire-20 (KVIQ-20). The Box and Block Test (BBT) and the Timed Up and Go (TUG) were employed for the temporal congruence component.ResultsThe mean ages of the Fatigued Group (30.4 ± 9.2 years) and the Non-fatigued Group (31.5 ± 9.8 years) were similar (P = .650). The fatigued Group exhibited significantly lower kinesthetic imagery scores on the KVIQ-20 (P = .028) and significantly lower performance in the BBT (upper extremities) mental chronometry test for both the most affected and least affected sides of the upper extremities (P = .007 and .028, respectively). Additionally, the Fatigued Group showed significantly lower performance in the TUG (lower extremities) mental chronometry test (P = .006).ConclusionIn fatigued individuals with MS, there is a greater impact on both temporal congruence components and kinesthetic motor imagery abilities. The difference in the temporal congruence component was observed in tests involving both TUG (lower extremities) and BBT (upper extremities), independent of the affected side.

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

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

Speed-accuracy trade-offs in action perception, motor imagery, and execution of hand movements in autistic and non-autistic adults

Action perception, execution, and imagery share motor-cognitive processes. Given prevalent sensory and motor coordination difficulties in autism, the processes of action perception and imagery may also be altered. This study investigated whether autistic adults can engage in motor imagery by testing potential differences in executing, perceiving, and imagining hand movements between autistic and non-autistic adults. Twenty autistic individuals and twenty age- and IQ-matched controls completed execution, imagination, and perception tasks using a Fitts' Law paradigm in an online session. For the execution and imagination tasks, participants performed or imagined making aiming movements between two targets. For the action perception task, participants indicated whether they could perform as accurately as the movements in presented videos. Target size and distance were manipulated into three difficulty levels and systematically varied across all tasks. Results showed Fitts' Law relationships for all tasks for both groups, with significant positive correlations between movement times and difficulty level. Movement times were longest in the imagination task and shortest in the perception task for both groups. These findings suggest motor imagery processes are relatively intact in autistic adults, highlighting that further investigation of motor imagery as a therapy for motor coordination difficulties in autistic individuals is warranted.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Action observation with motor simulation of reactive stepping: A randomized study in older adults with a history of falls

BACKGROUND

Perturbation-based training improves reactive stepping responses to prevent falling following a loss-of-balance. As there is currently no safe and feasible method for home-based practice, this randomized study investigated whether action observation with motor simulation (AOMS) of balance recovery improves reactive stepping in older adults with a history of falls. Additionally, we evaluated whether effects differ between AOMS of a human actor in the same experimental context or of an avatar in a virtual world.

METHODS

Seventy participants with a history of falls (68.3 ± 5.2y/o;52f) were subjected to 20 balance perturbations eliciting backward reactive steps. The AOMS group was tested after simulation of 20 reactive steps demonstrated by either a human actor (HumanAOMS) or a virtual avatar (AvatarAOMS). The control group was tested without prior observation. The primary outcome was reactive step quality, quantified as the leg angle at stepping-foot contact.

RESULTS

Differences between groups in the first perturbation trial were not significant. Upon repeated trials, both AOMS groups improved reactive step quality substantially faster than the control group. AOMS participants required on average five repetitions to achieve a reactive step quality that was no longer different from final performance in the last trial, whereas the control group needed ten. Both HumanAOMS and AvatarAOMS yielded similar gains.

CONCLUSIONS

The lack of effect in the first trial suggests that AOMS alone may not be sufficient for preventing real-life falls in this population. A next step would be to investigate whether this could be achieved by combining brief real perturbation practice with AOMS.

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

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

Measures of mental imagery in emotional disorders: A COSMIN systematic review of psychometric properties

BACKGROUND

Dysfunctional imagery processes characterise a range of emotional disorders. Valid, reliable, and responsive mental imagery measures may support the clinical assessment of imagery and advance research to develop theory and imagery-based interventions. We sought to review the psychometric properties of mental imagery measures relevant to emotional disorders.

METHODS

A systematic review registered on the Open Science Framework was conducted using COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guidance. Five databases were searched. COSMIN tools were used to assess the quality of study methodologies and psychometric properties of measures.

RESULTS

Twenty-three articles describing twenty-one self-report measures were included. Measures assessed various imagery processes and were organised into four groups based on related emotional disorders. Study methodological quality varied: measure development and reliability studies were generally poor, while internal consistency and hypothesis testing studies were higher quality. Most measurement properties assessed were of indeterminate quality.

CONCLUSION

Imagery measures were heterogenous and primarily disorder specific. Due to a lack of high-quality psychometric assessment, it is unclear whether most included imagery measures are valid, reliable, or responsive. Measures had limited evidence of content validity suggesting further research could engage clinical populations to ensure their relevance and comprehensiveness.

White matter organisation of sensorimotor tracts is associated with motor imagery in childhood

Despite the important role of motor imagery (MI) in motor development, our understanding of the contribution of white matter fibre properties to MI performance in childhood remains limited. To provide novel insight into the white matter correlates of MI performance, this study examined the association between white matter fibre properties and motor imagery performance in a sample of typically developing children. High angular diffusion weighted imaging data were collected from 22 typically developing children aged 6-14 years (12 female, MAge= 10.56). Implicit motor imagery performance was assessed using a mental hand rotation paradigm. The cerebellar peduncles and the superior longitudinal fasciculus were reconstructed using TractSeg, a semi-automated method. For each tract, white matter microstructure (fibre density, FD) and morphology (fibre bundle cross-section, FC) were estimated using Fixel-Based Analysis. Permutation-based inference testing and partial correlation analyses demonstrated that higher FC in the middle cerebellar peduncles was associated with better MI performance. Tract-based region of interest analyses showed that higher FC in the middle and superior cerebellar peduncles were associated with better MI performance. Results suggest that white matter connectivity along the cerebellar peduncles may facilitate MI performance in childhood. These findings advance our understanding of the neurobiological systems that underlie MI performance in childhood and provide early evidence for the relevance of white matter sensorimotor pathways to internal action representations.

The multisensory nature of human action imagery

Imagination can appeal to all our senses and may, therefore, manifest in very different qualities (e.g., visual, tactile, proprioceptive, or kinesthetic). One line of research addresses action imagery that refers to a process by which people imagine the execution of an action without actual body movements. In action imagery, visual and kinesthetic aspects of the imagined action are particularly important. However, other sensory modalities may also play a role. The purpose of the paper will be to address issues that include: (i) the creation of an action image, (ii) how the brain generates images of movements and actions, (iii) the richness and vividness of action images. We will further address possible causes that determine the sensory impression of an action image, like task specificity, instruction and experience. In the end, we will outline open questions and future directions.

Anodal transcranial direct current stimulation does not enhance the effects of motor imagery training of a sequential finger-tapping task in young adults

When applied over the primary motor cortex (M1), anodal transcranial direct current stimulation (a-tDCS) could enhance the effects of a single motor imagery training (MIt) session on the learning of a sequential finger-tapping task (SFTT). This study aimed to investigate the effect of a-tDCS on the learning of an SFTT during multiple MIt sessions. Two groups of 16 healthy young adults participated in three consecutive MIt sessions over 3 days, followed by a retention test 1 week later. They received active or sham a-tDCS during a MIt session in which they mentally rehearsed an eight-item complex finger sequence with their left hand. Before and after each session, and during the retention test, they physically repeated the sequence as quickly and accurately as possible. Both groups (i) improved their performance during the first two sessions, showing online learning; (ii) stabilised the level they reached during all training sessions, reflecting offline consolidation; and (iii) maintained their performance level one week later, showing retention. However, no significant difference was found between the groups, regardless of the MSL stage. These results emphasise the importance of performing several MIt sessions to maximise performance gains, but they do not support the additional effects of a-tDCS.

Motor imagery in autism: a systematic review

Introduction

Motor Imagery (MI) is when an individual imagines performing an action without physically executing that action and is thought to involve similar neural processes used for execution of physical movement. As motor coordination difficulties are common in autistic individuals it is possible that these may affect MI ability. The aim of this systematic review was to assess the current knowledge around MI ability in autistic individuals.

Methods

A systematic search was conducted for articles published before September 2023, following PRISMA guidance. Search engines were PsycINFO, PubMed, Web of Science, Scopus, Wiley Online Library and PsyArXiv. Inclusion criteria included: (a) Original peer-reviewed and pre-print publications; (b) Autistic and a non-autistic group (c) Implicit or explicit imagery tasks (d) Behavioral, neurophysiological or self-rating measures, (e) Written in the English language. Exclusion criteria were (a) Articles only about MI or autism (b) Articles where the autism data is not presented separately (c) Articles on action observation, recognition or imitation only (d) Review articles. A narrative synthesis of the evidence was conducted.

Results

Sixteen studies across fourteen articles were included. Tasks were divided into implicit (unconscious) or explicit (conscious) MI. The implicit tasks used either hand (6) or body (4) rotation tasks. Explicit tasks consisted of perspective taking tasks (3), a questionnaire (1) and explicit instructions to imagine performing a movement (2). A MI strategy was apparent for the hand rotation task in autistic children, although may have been more challenging. Evidence was mixed and inconclusive for the remaining task types due to the varied range of different tasks and, measures conducted and design limitations. Further limitations included a sex bias toward males and the hand rotation task only being conducted in children.

Discussion

There is currently an incomplete understanding of MI ability in autistic individuals. The field would benefit from a battery of fully described implicit and explicit MI tasks, conducted across the same groups of autistic children and adults. Improved knowledge around MI in autistic individuals is important for understanding whether MI techniques may benefit motor coordination in some autistic people.

Neural underpinnings of the interplay between actual touch and action imagination in social contexts

While there is established evidence supporting the involvement of the sense of touch in various actions, the neural underpinnings of touch and action interplay in a social context remain poorly understood. To prospectively investigate this phenomenon and offer further insights, we employed a combination of motor and sensory components by asking participants to imagine exerting force with the index finger while experiencing their own touch, the touch of one another individual, the touch of a surface, and no touch. Based on the assumption that the patterns of activation in the motor system are similar when action is imagined or actually performed, we proceeded to apply a single-pulse transcranial magnetic stimulation over the primary motor cortex (M1) while participants engaged in the act of imagination. Touch experience was associated with higher M1 excitability in the presence and in the absence of force production imagination, but only during force production imagination M1 excitability differed among the types of touch: both biological sources, the self-touch and the touch of one other individual, elicited a significant increase in motor system activity when compared to touching a non-living surface or in the absence of touch. A strong correlation between individual touch avoidance questionnaire values and facilitation in the motor system was present while touching another person, indicating a social aspect for touch in action. The present study unveils the motor system correlates when the sensory/motor components of touch are considered in social contexts.

More implicit and more explicit motor imagery tasks for exploring the mental representation of hands and feet in action

The mental representation of the body in action can be explored using motor imagery (MI) tasks. MI tasks can be allocated along a continuum going from more implicit to more explicit tasks, where the discriminant is the degree of action monitoring required to solve the tasks (which is the awareness of using the mental representation of our own body to monitor our motor imagery). Tasks based on laterality judgments, such as the Hand Laterality Task (HLT) and the Foot Laterality Task (FLT), provide an example of more implicit tasks (i.e., less action monitoring is required). While, an example of a more explicit task is the Mental Motor Chronometry task (MMC) for hands and feet, where individuals are asked to perform or imagine performing movements with their limbs (i.e., more action monitoring is required). In our study, we directly compared hands and feet at all these tasks for the first time, as these body districts have different physical features as well as functions. Fifty-five participants were asked to complete an online version of the HLT and FLT (more implicit measure), and an online version of the MMC task for hands and feet (more explicit measure). The mental representation of hands and feet in action differed only when the degree of action monitoring decreased (HLT ≠ FLT); we observed the presence of biomechanical constraints only for hands. Differently, when the degree of action monitoring increased hands and feet did not show any difference (MMC hands = MMC feet). Our results show the presence of a difference in the mental representation of hands and feet in action that specifically depends on the degree of action monitoring.

Validation of the Slovenian Version of the Movement Imagery Questionnaire for Children (MIQ-C): A Measurement Tool to Assess the Imagery Ability of Motor Tasks in Children

Purpose

The ability to perform motor imagery has been shown to influence individual athletic performance and rehabilitation. Recent evidence supports its potential as a training tool to improve motor skills in children. Although there is a standardized assessment of the imagery abilities in Slovenian-speaking adults, there is currently no validated instrument for use with Slovenian children. Therefore, the aim of the present study was to conduct a linguistic validation study of the movement imagery questionnaire for children (MIQ-C).

Methods

A total of 100 healthy children (mean age 10.3±1.3 years; 50 female) were assessed with a Slovenian version of the MIQ-C at Day 1 and Day 8. Inter-day agreement was examined using intraclass correlation coefficients (ICC). Construct validity and internal consistency were assessed using a Cronbach's alpha coefficient and exploratory - confirmatory factor analysis, respectively.

Results

The test-retest ICC were very high for all three scales examined (ICCKI=0.90; ICCIVI=0.92; ICCEVI=0.90). Excellent internal consistency (up to 0.90) was found for kinaesthetic and both visual imageries. Confirmatory analysis confirmed a three-factorial structure of the MIQ-C.

Conclusions

The Slovenian version of the MIQ-C proved to be highly reliable and valid in assessing children's motor imagery abilities, and as such for use with Slovene-speaking children. Moreover, this standardized instrument can be a helpful tool in training and rehabilitation practice with children aged 7-12 years.

Handedness effects on imagery of dominant- versus non-dominant-hand movements: An electroencephalographic investigation

Mental representations of our bodies are thought to influence how we interact with our surroundings. We can examine these mental representations through motor imagery, the imagination of movement using scalp EEG recordings. The visual modality of motor imagery emphasises 'seeing' the imagined movement and is associated with increased activity in the alpha rhythm (8-14 Hz) measured over the occipital regions. The kinaesthetic modality emphasises 'feeling' the movement and is associated with decreased activity in the mu rhythm (8-14 Hz) measured over the sensorimotor cortices. These two modalities can be engaged in isolation or together. We recorded EEG activity while 37 participants (17 left-hand dominant) completed an objective hand motor imagery task. Left-handers exhibited significant activity differences between occipital and motor regions only during imagery of right-hand (non-dominant-hand) movements. This difference was primarily driven by less oscillatory activity in the mu rhythm, which may reflect a shift in imagery strategy wherein participants placed more effort into generating the kinaesthetic sensations of non-dominant-hand imagery. Spatial features of 8-14 Hz activity generated from principal component analysis (PCA) provide further support for a strategy shift. Right-handers also exhibited significant differences between alpha and mu activity during imagery of non-dominant movements. However, this difference was not primarily driven by either rhythm, and no differences were observed in the group's PCA results. Together, these findings indicate that individuals imagine movement differently when it involves their dominant versus non-dominant hand, and left-handers may be more flexible in their motor imagery strategies.

Interplay Between Innovation and Intersubjectivity: Therapists Perceptions of Phantom Motor Execution Therapy and Its Effect on Phantom Limb Pain

Purpose

Interpersonal processes, including therapeutic alliance, may modulate the impact of interventions on pain experience. However, the role of interpersonal context on the effects of technology-enhanced interventions remains underexplored. This study elicited therapists' perspectives on how a novel rehabilitative process, involving Phantom Motor Execution (PME), may impact phantom limb pain. The mediating role of therapeutic alliance, and the way PME influenced its formation, was investigated.

Methods

A qualitative descriptive design, using a framework method, was used to explore therapists' (n=11) experiences of delivering PME treatment. Semi-structured online-based interviews were conducted.

Results

A 3-way interaction between therapist, patient, and the PME device was an overarching construct tying four themes together. It formed the context for change in phantom limb experience. The perceived therapeutic effects (theme 1) extended beyond those initially hypothesised and highlighted the mediating role of the key actors and context (theme 2). The therapeutic relationship was perceived as a transformative journey (theme 3), creating an opportunity for communication, collaboration, and bonding. It was seen as a cause and a consequence of therapeutic effects. Future directions, including the role of expertise-informed adaptations and enabling aspects of customised solutions, were indicated (theme 4).

Conclusion

This study pointed to intrapersonal, interpersonal, and contextual factors that should be considered in clinical implementation of novel rehabilitative tools. The results demonstrated that therapists have unique insights and a crucial role in facilitating PME treatment. The study highlighted the need to consider the biopsychosocial model of pain in designing, evaluating, and implementing technology-supported interventions.

A case for hybrid BCIs: combining optical and electrical modalities improves accuracy

Near-infrared spectroscopy (NIRS) is a promising research tool that found its way into the field of brain-computer interfacing (BCI). BCI is crucially dependent on maximized usability thus demanding lightweight, compact, and low-cost hardware. We designed, built, and validated a hybrid BCI system incorporating one optical and two electrical modalities ameliorating usability issues. The novel hardware consisted of a NIRS device integrated with an electroencephalography (EEG) system that used two different types of electrodes: Regular gelled gold disk electrodes and tri-polar concentric ring electrodes (TCRE). BCI experiments with 16 volunteers implemented a two-dimensional motor imagery paradigm in off- and online sessions. Various non-canonical signal processing methods were used to extract and classify useful features from EEG, tEEG (EEG through TCRE electrodes), and NIRS. Our analysis demonstrated evidence of improvement in classification accuracy when using the TCRE electrodes compared to disk electrodes and the NIRS system. Based on our synchronous hybrid recording system, we could show that the combination of NIRS-EEG-tEEG performed significantly better than either single modality only.

EEG-Based BCIs on Motor Imagery Paradigm Using Wearable Technologies: A Systematic Review

In recent decades, the automatic recognition and interpretation of brain waves acquired by electroencephalographic (EEG) technologies have undergone remarkable growth, leading to a consequent rapid development of brain-computer interfaces (BCIs). EEG-based BCIs are non-invasive systems that allow communication between a human being and an external device interpreting brain activity directly. Thanks to the advances in neurotechnologies, and especially in the field of wearable devices, BCIs are now also employed outside medical and clinical applications. Within this context, this paper proposes a systematic review of EEG-based BCIs, focusing on one of the most promising paradigms based on motor imagery (MI) and limiting the analysis to applications that adopt wearable devices. This review aims to evaluate the maturity levels of these systems, both from the technological and computational points of view. The selection of papers has been performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), leading to 84 publications considered in the last ten years (from 2012 to 2022). Besides technological and computational aspects, this review also aims to systematically list experimental paradigms and available datasets in order to identify benchmarks and guidelines for the development of new applications and computational models.

Motor imagery vividness and symptom severity in Parkinson's disease

Motor imagery (MI), the mental simulation of movement in the absence of overt motor output, has demonstrated potential as a technique to support rehabilitation of movement in neurological conditions such as Parkinson's disease (PD). Existing evidence suggests that MI is largely preserved in PD, but previous studies have typically examined global measures of MI and have not considered the potential impact of individual differences in symptom presentation on MI. The present study investigated the influence of severity of overall motor symptoms, bradykinesia and tremor on MI vividness scores in 44 individuals with mild to moderate idiopathic PD. Linear mixed effects modelling revealed that imagery modality and the severity of left side bradykinesia significantly influenced MI vividness ratings. Consistent with previous findings, participants rated visual motor imagery (VMI) to be more vivid than kinesthetic motor imagery (KMI). Greater severity of left side bradykinesia (but not right side bradykinesia) predicted increased vividness of KMI, while tremor severity and overall motor symptom severity did not predict vividness of MI. The specificity of the effect of bradykinesia to the left side may reflect greater premorbid vividness for the dominant (right) side or increased attention to more effortful movements on the left side of the body resulting in more vivid motor imagery.

Atypical influence of biomechanical knowledge in Complex Regional Pain Syndrome-towards a different perspective on body representation

Part of the multifaceted pathophysiology of Complex Regional Pain Syndrome (CRPS) is ascribed to lateralized maladaptive neuroplasticity in sensorimotor cortices, corroborated by behavioral studies indicating that patients present difficulties in mentally representing their painful limb. Such difficulties are widely measured with hand laterality judgment tasks (HLT), which are also used in the rehabilitation of CRPS to activate motor imagery and restore the cortical representation of the painful limb. The potential of these tasks to elicit motor imagery is critical to their use in therapy, yet, the influence of the body's biomechanical constraints (BMC) on HLT reaction time, supposed to index motor imagery activation, is rarely verified. Here we investigated the influence of BMC on the perception of hand postures and movements in upper-limb CRPS. Patients were slower than controls in judging hand laterality, whether or not stimuli corresponded to their painful hand. Reaction time patterns reflecting BMC were mostly absent in CRPS and controls. A second experiment therefore directly investigated the influence of implicit knowledge of BMC on hand movement judgments. Participants judged the perceived path of movement between two depicted hand positions, with only one of two proposed paths that was biomechanically plausible. While the controls mostly chose the biomechanically plausible path, patients did not. These findings show non-lateralized body representation impairments in CRPS, possibly related to difficulties in using correct knowledge of the body's biomechanics. Importantly, they demonstrate the challenge of reliably measuring motor imagery with the HLT, which has important implications for the rehabilitation with these tasks.

A sequential learning model with GNN for EEG-EMG-based stroke rehabilitation BCI

Introduction

Brain-computer interfaces (BCIs) have the potential in providing neurofeedback for stroke patients to improve motor rehabilitation. However, current BCIs often only detect general motor intentions and lack the precise information needed for complex movement execution, mainly due to insufficient movement execution features in EEG signals.

Methods

This paper presents a sequential learning model incorporating a Graph Isomorphic Network (GIN) that processes a sequence of graph-structured data derived from EEG and EMG signals. Movement data are divided into sub-actions and predicted separately by the model, generating a sequential motor encoding that reflects the sequential features of the movements. Through time-based ensemble learning, the proposed method achieves more accurate prediction results and execution quality scores for each movement.

Results

A classification accuracy of 88.89% is achieved on an EEG-EMG synchronized dataset for push and pull movements, significantly outperforming the benchmark method's performance of 73.23%.

Discussion

This approach can be used to develop a hybrid EEG-EMG brain-computer interface to provide patients with more accurate neural feedback to aid their recovery.

Consistent under-reporting of task details in motor imagery research

Motor Imagery is a subject of longstanding scientific interest. However, critical details of motor imagery protocols are not always reported in full, hampering direct replication and translation of this work. The present review provides a quantitative assessment of the prevalence of under-reporting in the recent motor imagery literature. Publications from the years 2018-2020 were examined, with 695 meeting the inclusion criteria for further examination. Of these studies, 64% (445/695) did not provide information about the modality of motor imagery (i.e., kinesthetic, visual, or a mixture of both) used in the study. When visual or mixed imagery was specified, the details of the visual perspective to be used (i.e., first person, third person, or combinations of both) were not reported in 24% (25/103) of studies. Further analysis indicated that studies using questionnaires to assess motor imagery reported more information than those that did not. We conclude that studies using motor imagery consistently under-report key details of their protocols, which poses a significant problem for understanding, replicating, and translating motor imagery effects.

Implicit motor imagery performance and cortical activity throughout the menstrual cycle

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

Advanced aging effects on implicit motor imagery and its links to motor performance: An investigation via mental rotation of letters, hands, and feet

This study focuses on changes in implicit motor imagery during advanced aging and these changes’ co-occurrences with physical motor deficits. We administered a mental rotation (MR) task with letters, hands, and feet to 28 young adults (20–27 years) and to 71 older adults (60–87 years), and assessed motor skills (gait mobility and hand dexterity) and neuropsychological performance. Compared to young adults, older adults showed lower MR performance for all stimuli and stronger biomechanical constraint effects on both hand and foot rotation. Moreover, the foot biomechanical constraint effect continued to increase during late adulthood, and declines in hand and foot motor imagery emerged at earlier old ages than declines in visual imagery. These results first demonstrated distinct aging trajectories of hand motor imagery, foot motor imagery, and visual imagery. Exploratory partial correlation analysis for older adults showed positive associations of low-level perceptual-motor skills (Trail Making Test-A performance) with hand and foot MR performance and positive associations of mobility (Timed Up and Go test performance) with foot and letter MR performance. These associations exhibited somewhat different patterns from those of young adults and raised the possibility that age-related declines in motor (and visual) imagery co-occur with declines in motor functioning.

Mental rotation of hands and objects in ageing and Parkinson's disease: differentiating motor imagery and visuospatial ability

Motor imagery supports motor learning and performance and has the potential to be a useful strategy for neurorehabilitation. However, motor imagery ability may be impacted by ageing and neurodegeneration, which could limit its therapeutic effectiveness. Motor imagery can be assessed implicitly using a hand laterality task (HLT), whereby laterality judgements are slower for stimuli corresponding to physically more difficult postures, as indicated by a “biomechanical constraint” effect. Performance is also found to differ between back and palm views of the hand, which may differentially recruit visual and sensorimotor processes. Older adults and individuals with Parkinson’s disease (PD) have shown altered performance on the HLT; however, the effects of both ageing and PD on laterality judgements for the different hand views (back and palm) have not been directly examined. The present study compared healthy younger, healthy older, and PD groups on the HLT, an object-based mental rotation task, and an explicit motor imagery measure. The older and PD groups were slower than the younger group on the HLT, particularly when judging laterality from the back view, and exhibited increased biomechanical constraint effects for the palm. While response times were generally similar between older and PD groups, the PD group showed reduced accuracy for the back view. Letter rotation was slower and less accurate only in the PD group, while explicit motor imagery ratings did not differ significantly between groups. These results suggest that motor imagery may be slowed but relatively preserved in both typical ageing and neurodegeneration, while a PD-specific impairment in visuospatial processing may influence task performance. The findings have implications for the use of motor imagery in rehabilitation protocols.

Cervical Spinal Lesion, Completeness of Injury, Stress, and Depression Reduce the Efficiency of Mental Imagery in People With Spinal Cord Injury

OBJECTIVES

The aims of this study were to assess the relationships of (1) clinical variables (age, level of injury, time since injury [TSI], and completeness of injury) and (2) psychological variables (stress and depression) with mental imagery ability in individuals with spinal cord injury.

STUDY DESIGN

This was a cross-sectional study. Participants with spinal cord injury (N = 130) were requested to fill the Kinesthetic and Visual Imagery Questionnaire and Vividness of Motor Imagery Questionnaire. They also completed the Perceived Stress Scale and Patient Health Questionnaire 9 for the assessment of stress and depression, respectively.

RESULTS

Mental imagery scores were found to be significantly low in cervical injuries (P < 0.001) as compared with thoracic injuries (P < 0.001). Furthermore, higher levels of spinal injuries resulted in lower mental imagery scores. Completeness of injury (according to Asia Impairment Scale) also had a significant relationship (P < 0.001) with the mental imagery ability among spinal cord injury participants. Presence of stress (P < 0.001) and depression (P < 0.001) also associated with reduced efficiency of mental imagery in these individuals.

CONCLUSIONS

Injury type and psychological factors were associated with mental imagery in SCI patients. Imagery-based interventions should be designed after consideration of identified factors yielding effect on their outcomes.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME.

CME OBJECTIVES

Upon completion of this article, the reader should be able to: (1) Determine the impact of clinical variables such as level of injury, completeness and chronicity of injury on mental imagery ability in spinal cord injury; (2) Discuss the role of stress and depression on mental imagery ability in spinal cord injury; and (3) Describe the various dimensions of mental imagery ability and its variability among individuals who have spinal cord injury.

LEVEL

Advanced.

ACCREDITATION

The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Imagery ability assessments: a cross-disciplinary systematic review and quality evaluation of psychometric properties

BACKGROUND

Over the last two centuries, researchers developed several assessments to evaluate the multidimensional construct of imagery. However, no comprehensive systematic review (SR) exists for imagery ability evaluation methods and an in-depth quality evaluation of their psychometric properties.

METHODS

We performed a comprehensive systematic search in six databases in the disciplines of sport, psychology, medicine, education: SPORTDiscus, PsycINFO, Cochrane Library, Scopus, Web of Science, and ERIC. Two reviewers independently identified and screened articles for selection. COSMIN checklist was used to evaluate the methodological quality of the studies. All included assessments were evaluated for quality using criteria for good measurement properties. The evidence synthesis was summarised by using the GRADE approach.

RESULTS

In total, 121 articles reporting 155 studies and describing 65 assessments were included. We categorised assessments based on their construct on: (1) motor imagery (n = 15), (2) mental imagery (n = 48) and (3) mental chronometry (n = 2). Methodological quality of studies was mainly doubtful or inadequate. The psychometric properties of most assessments were insufficient or indeterminate. The best rated assessments with sufficient psychometric properties were MIQ, MIQ-R, MIQ-3, and VMIQ-2 for evaluation of motor imagery ability. Regarding mental imagery evaluation, only SIAQ and VVIQ showed sufficient psychometric properties.

CONCLUSION

Various assessments exist to evaluate an individual's imagery ability within different dimensions or modalities of imagery in different disciplines. However, the psychometric properties of most assessments are insufficient or indeterminate. Several assessments should be revised and further validated. Moreover, most studies were only evaluated with students. Further cross-disciplinary validation studies are needed including older populations with a larger age range. Our findings allow clinicians, coaches, teachers, and researchers to select a suitable imagery ability assessment for their setting and goals based on information about the focus and quality of the assessments.

SYSTEMATIC REVIEWS REGISTER

PROSPERO CRD42017077004 .

Self-perception in anorexia nervosa: When the body becomes an object

OBJECTIVE

Women with anorexia nervosa (AN) act as if they have a larger body, as evidenced in obstacle avoidance tasks, where an allocentric perspective is adopted. This alteration emerges not only when they perform, but also when they imagine movements. However, no previous study has investigated own body centered tasks. As such, in this study we aim at documenting if women with AN show an altered behaviour also when the task requires a first-person perspective.

METHOD

We explored the performance of eleven woman affected by AN compared to eighteen matched controls, in two motor imagery tasks based on a self-frame of reference, the Hand Laterality Task and the Mental Motor Chronometry Task. Moreover, two control tasks relative to visual imagery were administered.

RESULTS

In the Hand Laterality Task, affected participants did not adopt a motor strategy to judge hands laterality (i.e. no biomechanical constraints effect). Crucially, they also showed an altered behavior in the control task. Similarly, they did not show the expected isochrony in the Mental Motor Chronometry Task, when actions pertained the left (but not the right) hand, in absence of any difference in the control task.

CONCLUSIONS

Our findings reveal altered imagery processes in AN. Specifically, affected participants adopt a third-person, rather than a first-person perspective, even when the task requires to imagine their own body in an internal frame of reference. In other words, participants with AN objectify body stimuli. Different mechanisms (i.e., checking behaviour; mirror self-reflection; altered multisensory integration) can explain such an altered imagery in AN.

Kinesthetic and visual imagery in young adults with chronic neck pain

Background:Young adults complain of neck pain almost every year. In recent years the ability of motor imagery (kinesthetic and visual imagery) in many musculoskeletal system problems other than neck pain in young adults has been investigated in the literature. The Cross-Sectional study aimed to question motor imagery ability in young adults with chronic neck pain. Methods: Two groups were included in the study: the chronic neck pain group (n = 83) and the control group (n = 91). Motor imagery ability of both groups was evaluated with Movement Imagery Questionnaire-3. Additionally, in the chronic neck pain group, pain was evaluated with the Short Form-McGill Pain Questionnaire, disability was evaluated with the Neck Disability Index, and kinesiophobia was evaluated with Tampa Scale for Kinesiophobia. Conclusions: Internal visual imagery and kinesthetic imagery were significantly different between chronic neck pain and control groups. There was a negative linear relationship between disability and internal visual imagery, external visual imagery, and kinesthetic imagery. Motor imagery ability is reduced in young adults with chronic neck pain. In addition, as the severity of disability increases, the motor imagery ability decreases. Therefore, it is considered appropriate to include a motor imagery training program when treating chronic neck pain in the future.

Behavioural indexes of movement imagery ability are associated with the magnitude of corticospinal adaptation following movement imagery training

Movement imagery (MI) is a cognitive process wherein an individual simulates themselves performing a movement in the absence of physical movement. The current paper reports an examination of the relationship between behavioural indexes of MI ability and the magnitude of corticospinal adaptation following MI training. Behavioural indexes of MI ability included data from a questionnaire (MIQ-3), a mental chronometry task, and a hand laterality judgment task. For the measure of corticospinal adaptation, single-pulse transcranial magnetic stimulation (TMS) was administered to elicit thumb movements to determine the representation of thumb movements before and after MI training. MI training involved participants imagining themselves moving their thumb in the opposite direction to the dominant direction of the TMS-evoked movements prior to training. Pre/post-training changes in the direction and velocity of TMS-evoked thumb movements indicated the magnitude of adaptation following MI training. The two main findings were: 1) a positive relationship was found between the MIQ-3 and the pre/post-training changes in the direction of TMS-evoked thumb movements; and 2) a negative relationship between the mental chronometry measure and both measures of corticospinal adaptation following MI training. These results indicate that both ease of imagery and timing of imagery could predict the magnitude of neuroplastic adaptation following MI training. Thus, both these measures may be considered when assessing imagery ability and determining who might benefit from MI interventions.

Deep and Wide Transfer Learning with Kernel Matching for Pooling Data from Electroencephalography and Psychological Questionnaires

Motor imagery (MI) promotes motor learning and encourages brain–computer interface systems that entail electroencephalogram (EEG) decoding. However, a long period of training is required to master brain rhythms’ self-regulation, resulting in users with MI inefficiency. We introduce a parameter-based approach of cross-subject transfer-learning to improve the performances of poor-performing individuals in MI-based BCI systems, pooling data from labeled EEG measurements and psychological questionnaires via kernel-embedding. To this end, a Deep and Wide neural network for MI classification is implemented to pre-train the network from the source domain. Then, the parameter layers are transferred to initialize the target network within a fine-tuning procedure to recompute the Multilayer Perceptron-based accuracy. To perform data-fusion combining categorical features with the real-valued features, we implement stepwise kernel-matching via Gaussian-embedding. Finally, the paired source–target sets are selected for evaluation purposes according to the inefficiency-based clustering by subjects to consider their influence on BCI motor skills, exploring two choosing strategies of the best-performing subjects (source space): single-subject and multiple-subjects. Validation results achieved for discriminant MI tasks demonstrate that the introduced Deep and Wide neural network presents competitive performance of accuracy even after the inclusion of questionnaire data.

A different point of view: the evaluation of motor imagery perspectives in patients with sensorimotor impairments in a longitudinal study

Background

Motor imagery (MI) has been successfully applied in neurological rehabilitation. Little is known about the spontaneous selection of the MI perspectives in patients with sensorimotor impairments. What perspective is selected: internal (first-person view), or external (third-person view)? The aim was to evaluate the MI perspective preference in patients with sensorimotor impairments.

Methods

In a longitudinal study including four measurement sessions, 55 patients (25 stroke, 25 multiple sclerosis, 5 Parkinson’s disease; 25 females; mean age 58 ± 14 years) were included. MI ability and perspective preference in both visual and kinaesthetic imagery modalities were assessed using the Kinaesthetic and Visual Imagery Questionnaire-20 (KVIQ-20), the body rotation task (BRT), and mental chronometry (MC). Additionally, patients’ activity level was assessed. Descriptive analyses were performed regarding different age- (< 45, 45–64, > 64), activity levels (inactive, partially active, active), and KVIQ-20 movement classifications (axial, proximal, distal, upper and lower limb). A mixed-effects model was used to investiage the relationship between the primary outcome (MI perspective: internal, external) with the explanatory variables age, MI modality (visual, kinaesthetic), movement type (axial, proximal, distal), activity levels and the different assessments (KVIQ-20, BRT, MC).

Results

Imagery modality was not a significant predictor of perspective preference. Over the four measurement sessions, patients tended to become more consistent in their perspective selection, however, time point was not a significant predictor. Movement type was a significant predictor: imagination of distal vs. axial and proximal vs. axial movements were both associated with preference for external perspective. Patients with increased physical activity level tend to use internal imagery, however, this effect was borderline not statistically significant. Age was neither a significant precictor. Regarding the MI assessments, the KVIQ- 20 score was a significant predictor. The patients with higher test scores tend to use the external perspective.

Conclusion

It is recommended to evaluate the spontaneous MI perspective selection to design patient-specific MI training interventions. Distal movements (foot, finger) may be an indicator when evaluating the consistency of the MI perspective in patients with sensorimotor impairments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02266-w.

Action Imagery and Observation in Neurorehabilitation for Parkinson's Disease (ACTION-PD): Development of a User-Informed Home Training Intervention to Improve Functional Hand Movements

Background

Parkinson's disease (PD) causes difficulties with hand movements, which few studies have addressed therapeutically. Training with action observation (AO) and motor imagery (MI) improves performance in healthy individuals, particularly when the techniques are applied simultaneously (AO + MI). Both AO and MI have shown promising effects in people with PD, but previous studies have only used these separately.

Objective

This article describes the development and pilot testing of an intervention combining AO + MI and physical practice to improve functional manual actions in people with PD.

Methods

The home-based intervention, delivered using a tablet computer app, was iteratively designed by an interdisciplinary team, including people with PD, and further developed through focus groups and initial field testing. Preliminary data on feasibility were obtained via a six-week pilot randomised controlled trial (ISRCTN 11184024) of 10 participants with mild to moderate PD (6 intervention; 4 treatment as usual). Usage and adherence data were recorded during training, and semistructured interviews were conducted with participants. Exploratory outcome measures included dexterity and timed action performance.

Results

Usage and qualitative data provided preliminary evidence of acceptability and usability. Exploratory outcomes also suggested that subjective and objective performance of manual actions should be tested in a larger trial. The importance of personalisation, choice, and motivation was highlighted, as well as the need to facilitate engagement in motor imagery.

Conclusions

The results indicate that a larger RCT is warranted, and the findings also have broader relevance for the feasibility and development of AO + MI interventions for PD and other conditions.

Mu oscillations and motor imagery performance: A reflection of intra-individual success, not inter-individual ability

Mu oscillations (8-13 Hz), recorded over the human motor cortex, have been shown to consistently suppress during both the imagination and performance of movements; however, its functional significance in the imagery process is currently unclear. Here we examined human electroencephalographic (EEG) oscillations in the context of motor imagery performance as measured by imagery success within participants and imagery ability between participants. We recorded continuous EEG activity while participants performed the Test of Ability in Movement Imagery (TAMI), an objective test of motor imagery task. Results demonstrated that mu oscillatory activity significantly decreased during successful as compared to unsuccessful imagery trials. However, the extent of reduction in mu oscillations did not correlate with overall imagery ability as measured by the total TAMI score. These findings provide further support for the involvement of mu oscillations in indexing motor imagery performance and suggest that mu oscillations may reflect important processes related to imagery accuracy, processes likely related to those underlying overt motor production and motor understanding.

The role of mirror mechanism in the recovery, maintenance, and acquisition of motor abilities

While it is well documented that the motor system is more than a mere implementer of motor actions, the possible applications of its cognitive side are still under-exploited, often remaining as poorly organized evidence. Here, we will collect evidence showing the value of action observation treatment (AOT) in the recovery of impaired motor abilities for a vast number of clinical conditions, spanning from traumatological patients to brain injuries and neurodegenerative diseases. Alongside, we will discuss the use of AOT in the maintenance of appropriate motor behavior in subjects at risk for events with dramatic physical consequences, like fall prevention in elderly people or injury prevention in sports. Finally, we will report that AOT can help to tune existing motor competencies in fields requiring precise motor control. We will connect all these diverse dots into the neurophysiological scenario offered by decades of research on the human mirror mechanism, discussing the potentialities for individualization. Empowered by modern technologies, AOT can impact individuals' safety and quality of life across the whole lifespan.

Automatic effects of covert practice

Automatic behaviour is supposedly underlain by the unintentional retrieval of processing episodes, which are stored during the repeated overt practice of a task or activity. In the present study, we investigated whether covertly practicing a task (e.g., repeatedly imagining responding to a stimulus) also leads to the storage of processing episodes and thus to automatic behaviour. Participants first either responded overtly or covertly to stimuli according to a first categorization task in a practice phase. We then measured the presence of automatic response-congruency effects in a subsequent test phase that involved a different categorization task but the same stimuli and responses. Our results indicate that covert practice can lead to a response-congruency effect. We conclude that covert practice can lead to automatic behaviour and discuss the different components of covert practice, such as motor imagery, visual imagery, and inner speech, that contribute to the formation of processing episodes in memory.

The effects of visual impairment on motor imagery in children and adolescents

BACKGROUND

While the development of motor imagery (MI) has been extensively studied in sighted children, it is not clear how children with different severities of visual impairment (VI) represent motor actions by using the motor representations constructed through the remaining intact senses, especially touch.

AIMS

Mental chronometry and generation/manipulation of MI were examined in children with and without VI.

METHODS AND PROCEDURES

Participants included 64 youth with and without VI (33 without visual impairments, 14 moderate-to-severe, and 17 blind). Mental chronometry was assessed with the imagined Timed-Up-and-Go-Test (iTUG), and generation/manipulation of MI with the Controllability-of-Motor-Imagery-Test (CMI). In addition, the effect of working memory performance (Letter-Number-Sequencing) and physical activity upon MI were evaluated.

RESULTS

Mental duration for the iTUG was significantly shorter than the active durations. Results also provided evidence of better haptic representation than motor representation in all participants; however, only for the CMI-regeneration condition controls outperformed children with visual impairments and blindness (CVIB). Exercise and working memory performance showed a significant contribution only on a few MI tests.

CONCLUSION AND IMPLICATIONS

Our results suggest a possible relationship between motor performance, body representation deficits and visual impairment which needs to be addressed in the evaluation and treatment of CVIB. The design of new rehabilitation interventions that focus on strengthening adequate body perception and representation should be proposed and tested to promote motor development in CVIB.

Effects of Motor Imagery Training on Balance and Gait in Older Adults: A Randomized Controlled Pilot Study

The aim of this study was to demonstrate the effects of motor imagery training on balance and gait abilities in older adults and to investigate the possible application of the training as an effective intervention against fall prevention. Subjects (n = 34) aged 65 years and over who had experienced falls were randomly allocated to three groups: (1) motor imagery training group (MITG, n = 11), (2) task-oriented training group (TOTG, n = 11), and (3) control group (CG, n = 12). Each group performed an exercise three times a week for 6 weeks. The dependent variables included Path Length of center of pressure (COP)-based static balance, Berg Balance Scale (BBS) score, Timed Up and Go Test (TUG) score, which assesses a person's mobility based on changes in both static and dynamic balance, Falls Efficacy Scale (FES) score, which evaluates changes in fear of falls, and gait parameters (velocity, cadence, step length, stride length, and H-H base support) to evaluate gait. After the intervention, Path Length, BBS, TUG, velocity, cadence, step length, and stride length showed significant increases in MITG and TOTG compared to CG (p < 0.05). Post hoc test results showed a significantly greater increase in BBS, TUG, and FES in MITG compared with TOTG and CG (p < 0.05). Our results suggest that motor imagery training combined with functional training has positive effects on balance, gait, and fall efficacy for fall prevention in the elderly.

Accuracy and Vividness in Motor Imagery Ability: Differences between Children and Young Adults

Motor imagery (MI) refers to the imagination of a motor task without actual movement execution. The purpose of this study was to compare MI accuracy and vividness, and motor proficiency between children (n = 101; 7-12 years) and young adults (n = 140; 18-25 years). Results indicated that young adults were significantly more accurate and rated their MI significantly more vivid than children. For MI accuracy, between-subject effects showed that young adults had higher scores than children on three of the four subscales and the action subscale significantly predicted motor proficiency. These findings indicate that MI ability continues to develop into adulthood.

Probing the Effect of Block Duration on Corticospinal Excitability during Motor Imagery Performance

Considerable evidence exists related to the behavioral outcomes of motor imagery-based training (MI). Comparatively, there is a relative gap in the literature on how corticospinal excitability, a precursor for experience-dependent plasticity, changes over the course of an MI session, and more specifically if there is an effect of varying the duration of the blocks in which MI is performed. As such, we probed corticospinal excitability during MI, whereby the duration of MI blocks within the session were manipulated yet total exposure to MI was kept constant. Participants performed a total of 24 min of MI of common motor tasks in blocks of 2, 4 or 6 min. Transcranial magnetic stimulation was used to assess corticospinal excitability throughout MI performance. All groups demonstrated increased corticospinal excitability over the session. Owing to a decrease in corticospinal excitability when engaging in 6 min blocks and the variability noted when engaging in 2 min blocks, findings suggest that MI performed in 4 min blocks may be preferable for the generation and maintenance of corticospinal excitability, at least relative to 2 and 6 min blocks. Overall, our findings provide physiological evidence that informs the structure of MI training sessions to optimize their effectiveness.

Investigating Priming Effects of Physical Practice on Motor Imagery-Induced Event-Related Desynchronization

For motor imagery (MI) to be effective, an internal representation of the to-be-imagined movement may be required. A representation can be achieved through prior motor execution (ME), but the neural correlates of MI that are primed by ME practice are currently unknown. In this study, young healthy adults performed MI practice of a unimanual visuo-motor task (Group MI, n = 19) or ME practice combined with subsequent MI practice (Group ME&MI, n = 18) while electroencephalography (EEG) was recorded. Data analysis focused on the MI-induced event-related desynchronization (ERD). Specifically, changes in the ERD and movement times (MT) between a short familiarization block of ME (Block pre-ME), conducted before the MI or the ME combined with MI practice phase, and a short block of ME conducted after the practice phase (Block post-ME) were analyzed. Neither priming effects of ME practice on MI-induced ERD were found nor performance-enhancing effects of MI practice in general. We found enhancements of the ERD and MT in Block post-ME compared to Block pre-ME, but only for Group ME&MI. A comparison of ME performance measures before and after the MI phase indicated however that these changes could not be attributed to the combination of ME and MI practice. The mixed results of this study may be a consequence of the considerable intra- and inter-individual differences in the ERD, introduced by specifics of the experimental setup, in particular the individual and variable task duration, and suggest that task and experimental setup can affect the interplay of ME and MI.

A general theory of consciousness I: Consciousness and adaptation

This paper examines how cognitive processes in living beings become conscious. Consciousness is often assumed to be a human quality only. While the basis of this paper is that consciousness is as much present in animals as it is in humans, the human form is shown to be fundamentally different. Animal consciousness expresses itself in sensory images, while human consciousness is largely verbal. Because spoken language is not an individual quality - thoughts are shared with others via communication - consciousness in humans is complex and difficult to understand. The theory proposed postulates that consciousness is an inseparable part of the body's adaptation mechanism. In adaptation to a new environmental disturbance, the outcome of the neural cognitive process - a possible solution to the problem posed by the disturbance - is transformed into a sensory image. Sensory images are essentially conscious as they are the way living creatures experience new environmental information. Through the conversion of neural cognitive activity - thoughts - about the state of the outside world into the way that world is experienced through the senses, the thoughts gain the reality that sensory images have. The translation of thoughts into sensory images makes them real and understandable which is experienced as consciousness. The theory proposed in this paper is corroborated by functional block diagrams of the processes involved in the complex regulated mechanism of adaptation and consciousness during an environmental disturbance. All functions in this mechanism and their interrelations are discussed in detail.

Dance and Parkinson's: A review and exploration of the role of cognitive representations of action

Parkinson's disease (PD) is a neurodegenerative condition that causes both sensorimotor and non-motor impairments, and there is a clear need for non-medical approaches to improve quality of life. Dance is an increasingly popular activity among people with PD, which demonstrates potential therapeutic benefits. However, findings to date have been inconsistent, and little is known about the mechanisms underlying benefits of dance in PD. In this review, we provide an overview of research into dance for people with PD. The majority of quantitative evidence is in the sensorimotor domain, but cognitive, psychological and social effects have also been reported. We consider the role of cognitive representations of action within dance through observation, imitation and imagery, which may contribute to both sensorimotor and non-motor outcomes for people with PD. Moreover, we discuss how these processes may be enhanced through dance to provide further benefits in everyday life. Finally, we propose avenues for future research to increase understanding of action representation in dance for PD, which has the potential to inform practice and maximize benefits.

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

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

WaveCSP: a robust motor imagery classifier for consumer EEG devices

There is an increasing demand for reliable motor imagery (MI) classification algorithms for applications in consumer level brain-computer interfacing (BCI). For the practical use, such algorithms must be robust to both device limitations and subject variability, which make MI classification a challenging task. This study proposes methods to study the effect of limitations including a limited number of electrodes, limited spatial distribution of electrodes, lower signal quality, subject variabilities and BCI literacy, on the performance of MI classification. To mitigate these limitations, we propose a machine learning approach, WaveCSP that uses 24 features extracted from EEG signals using wavelet transform and common spatial pattern (CSP) filtering techniques. The algorithm shows better performance in terms of subject variability compared to existing work. The application of WaveCSP to Physionet MI database shows more than 50% of the 109 subjects achieving accuracy higher than 64%. The data obtained from a commercial EEG headset using the same experimental protocol result in up to four out of five subjects who had prior BCI experience (out of a total of 25 subjects) performing with accuracy higher than 64%.

Motor imagery ability assessments in four disciplines: protocol for a systematic review

INTRODUCTION

Motor imagery (MI) is a very popular and well-accepted technique in different disciplines. Originating from sport and psychology, MI is now also used in the field of medicine and education. Several studies confirmed the benefits of MI to facilitate motor learning and skill acquisition. The findings indicated that individual's MI ability might influence the effectiveness of MI interventions. Over the last two centuries, researchers have developed several assessments to evaluate MI's abstract construct. However, no systematic reviews (SR) exist for MI ability evaluation methods and their measurement properties.

METHODS AND ANALYSIS

The SR will evaluate available MI ability assessments and their psychometric properties in four relevant disciplines: sports, psychology, medicine and education. This involves performing searches in SPORTDiscus, PsycINFO, Cochrane Library, Scopus, Web of Science and ERIC. Working independently, two reviewers will screen articles for selection. Then all raw information will be compiled in an overview table-including the articles' characteristics (eg, a study's setting or the population demographics) and the MI ability assessment (psychometric properties). To evaluate the articles' methodological quality, we will use the COSMIN checklist. Then we will evaluate all the included assessments' quality and perform a best-evidence synthesis. Results of this review will be reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

ETHICS AND DISSEMINATION

The SR is based on published data, and ethical approval is not required. This review will provide information on assessment performance and equipment, as well as its main focus and usefulness. Furthermore, we will present the methodological quality of all the included articles and assess the included instruments' quality. Ultimately, this will act as a valuable resource, providing an overview of MI ability assessments for individual clinical settings, treatment aims, and various populations. The SR's final report will be published in a peer-reviewed journal and presented at relevant conferences.

PROSPERO REGISTRATION NUMBER

CRD42017077004.

Motor imagery, performance and motor rehabilitation

Motor imagery has been central to adzvances in sport performance and rehabilitation. Neuroscience has provided techniques for measurement which have aided our understanding, conceptualization and theorizing. Challenges remain in the appropriate measurement of motor imagery. Motor imagery continues to provide an impetus for new findings relating to our emotional network, embodied cognition, inhibitory processes and action representation. New directions are proposed which include exploring the physical setting and conditions in which imagery occurs and investigating if short term impairments to the motor system detract from motor imagery ability and the potential application of motor imagery for recovery.

Movement imagery as a predictor of online control in typically developing children

The ability to mentally represent actions is suggested to play a role in the online control of movement in healthy adults. Children's movement imagery ability and online control have been shown to develop at similar nonlinear rates. The current study investigated the relationship between movement imagery and online control in children by comparing implicit and explicit movement imagery measures with the ability to make online trajectory corrections. Imagery ability was a significant predictor of children's online control of movement once general reaching efficiency was controlled for. These findings extend the proposed relationship between movement imagery and online control.

Motor command inhibition and the representation of response mode during motor imagery

Research on motor imagery proposes that overt actions during motor imagery can be avoided by proactively signaling subthreshold motor commands to the effectors and by invoking motor-command inhibition. A recent study by Rieger, Dahm, and Koch (2017) found evidence in support of motor command inhibition, which indicates that MI cannot be completed on the sole basis of subthreshold motor commands. However, during motor imagery, participants know in advance when a covert response is to be made and it is thus surprising such additional motor-command inhibition is needed. Accordingly, the present study tested whether the demand to perform an action covertly can be proactively integrated by investigating the formation of task-specific action rules during motor imagery. These task-specific action rules relate the decision rules of a task to the mode in which these rules need to be applied (e.g., if smaller than 5, press the left key covertly). To this end, an experiment was designed in which participants had to switch between two numerical judgement tasks and two response modes: covert responding and overt responding. First, we observed markers of motor command inhibition and replicated the findings of Rieger and colleagues. Second, we observed evidence suggesting that task-specific action rules are created for the overt response mode (e.g., if smaller than 5, press the left key). In contrast, for the covert response mode, no task-specific action rules are formed and decision rules do not include mode-specific information (e.g., if smaller than 5, left).