Why motor imagery is not really motoric: towards a re-conceptualization in terms of effect-based action control

Even with exposure to errors, motor imagery cannot update internal models

Recent evidence suggests that motor imagery is insufficient for updating internal models, essential for predicting and refining overt movement outcomes. The covert nature of motor imagery limits exposure to errors, perhaps preventing the updating of internal models. To explore this, 90 participants were exposed to a prism that shifted vision leftward, completing 20 physical pointing trials followed by either 230 more physical pointing trials [physical practice (PP)], 230 imagined pointing trials [physical practice motor imagery (PP-MI)], 230 unrelated task trials [physical practice control (PP-CTRL)], or no further trials [physical practice none (PP-None)]. We hypothesized that if exposure to errors is needed for motor imagery to update internal models, then PP-MI would exhibit aftereffects, characterized by pointing opposite to the prism shift (i.e., rightwards), similar to PP, but differing from PP-CTRL and PP-None. After prism exposure, all groups showed significant aftereffects (PP: 4.73° ± 2.12°, PP-MI: 2.62 ± 1.61, PP-CTRL: 2.58 ± 1.53, PP-None: 3.11 ± 1.68), however there were no significant differences in the magnitude of aftereffects between PP-MI, and PP-CTRL/PP-None. Our findings demonstrate that motor imagery alone is insufficient for updating internal models, even when participants are initially exposed to errors under a prism shift. This further reinforces that motor imagery is not a direct simulation of overt movement, as proposed by Motor Simulation Theory- the foundation for its use in rehabilitation. Deepening our understanding of how learning occurs through motor imagery is crucial for enhancing its effectiveness in practical applications like rehabilitation.

Motor imagery enhances performance beyond the imagined action

Motor imagery is frequently utilized to improve the performance of specific target movements in sports and rehabilitation. In this study, we show that motor imagery can facilitate learning of not only the imagined target movements but also sequentially linked overt movements. Hybrid sequences comprising imagined and physically executed segments allowed participants to learn specific movement characteristics of the executed segments when they were consistently associated with specific imagined segments. Electrophysiological recordings revealed that the degree of event-related synchronization in the alpha and beta bands during a basic motor imagery task was correlated with imagery-evoked motor learning. Thus, both behavioral and neural evidence indicate that motor imagery's benefits extend beyond the imagined movements, improving performance in linked overt movements. This provides decisive evidence for the functional equivalence of imagined and overt movements and suggests applications for imagery in sports and rehabilitation.

Let's do it: Response times in Mental Paper Folding and its execution

Action imagery is the ability to mentally simulate the execution of an action without physically performing it. Action imagery is assumed to rely at least partly on similar mechanisms as action execution. Therefore, we expected that imagery and execution durations would be constrained by the number of folds in a Paper Folding Task. Analogously, individual differences in execution durations were expected to be reflected in imagery durations. Twenty-eight participants performed two imagery conditions (computer vs. paper) and one execution condition (paper) where two-dimensional grids of a three-dimensional cube were (mentally) folded to determine whether two selected edges overlapped or not. As expected, imagery performance and execution performance were strongly correlated and decreased with the number of folds. Further, the number of folds influenced imagery durations even more than execution durations. This may be due to the additional cognitive load in imagery that emerges when tracking the folds to follow up with the next ones. The results indicate that Mental Paper Folding predominantly involves dynamic visual representations that are not functionally associated with one's own movements as in action imagery.

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

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

Enhancing motor imagery practice using synchronous action observation

In this paper, we discuss a variety of ways in which practising motor actions by means of motor imagery (MI) can be enhanced via synchronous action observation (AO), that is, by AO + MI. We review the available research on the (mostly facilitatory) behavioural effects of AO + MI practice in the early stages of skill acquisition, discuss possible theoretical explanations, and consider several issues related to the choice and presentation schedules of suitable models. We then discuss considerations related to AO + MI practice at advanced skill levels, including expertise effects, practical recommendations such as focussing attention on specific aspects of the observed action, using just-ahead models, and possible effects of the perspective in which the observed action is presented. In section "Coordinative AO + MI", we consider scenarios where the observer imagines performing an action that complements or responds to the observed action, as a promising and yet under-researched application of AO + MI training. In section "The dual action simulation hypothesis of AO + MI", we review the neurocognitive hypothesis that AO + MI practice involves two parallel action simulations, and we consider opportunities for future research based on recent neuroimaging work on parallel motor representations. In section "AO + MI training in motor rehabilitation", we review applications of AO, MI, and AO + MI training in the field of neurorehabilitation. Taken together, this evidence-based, exploratory review opens a variety of avenues for future research and applications of AO + MI practice, highlighting several clear advantages over the approaches of purely AO- or MI-based practice.

Imagery and motor learning: a special issue on the neurocognitive mechanisms of imagery and imagery practice of motor actions

Human beings are able to imagine actions with the aim to change movement coordination and to learn particular movements. Meta-analyses to date have shown that when individuals systematically engage in imagery of a motor action without overt behavior this can improve motor performance and facilitate motor learning. Despite a considerable body of research in neuroscience, psychology, and sport science, however, there is at present no consensus on the neurocognitive mechanisms of imagery, and the mechanisms that lead to learning via imagined action are still being debated. In particular, the differences between imagined and overt action, and respective learning effects, remain to be fully explained. The present collection of manuscripts is a result of compiling both theoretical advances in the field of motor control and motor learning and those in imagery research to better understand imagery and learning. It is structured alongside five position papers from leading experts in the field, each of which is followed by a series of short commentaries written by experts from various disciplines. This collection demonstrates (a) that conceptualizations of imagery are manifold, vary highly and depend on the perspective chosen, (b) that existing approaches to the neurocognitive mechanisms of imagery and imagery practice of motor actions draw on distinct motor control and learning perspectives, (c) that perspectives from the wider fields of motor control and learning stimulate new approaches to explain imagery and imagery practice, (d) and that future research is needed to investigate and compare different perspectives and conceptualizations of the neurocognitive mechanisms of imagery and imagery practice of motor actions.

Motor imagery from brain to muscle: a commentary on Bach et al., (2022)

In a recent article entitled "Why motor imagery is not really motoric: towards a re-conceptualization in terms of effect-based action control", Bach et al. nicely renewed the concept of motor equivalence between actual movement and motor imagery (MI), i.e. the mental simulation of an action without its corresponding motor output. Their approach is largely based on behavioral studies and, to a lesser extent, on the literature using cerebral imagery. However, the literature on cortico-spinal circuitry modulation during MI can provide further, interesting aspects. Indeed, when it comes to addressing the motor system, one should consider the whole path from brain region to muscle contraction, including sub-cortical structures such as the spinal circuitry. This commentary aims at bridging this gap by providing supplemental evidence and outlining a complementary approach.

Towards formal models of inhibitory mechanisms involved in motor imagery: a commentary on Bach et al. (2022)

A vast body of research suggests that the primary motor cortex is involved in motor imagery. This raises the issue of inhibition: how is it possible for motor imagery not to lead to motor execution? Bach et al. (Psychol Res Psychol Forschung. 10.1007/s00426-022-01773-w, 2022, this issue) suggest that the motor execution threshold may be "upregulated" during motor imagery to prevent execution. Alternatively, it has been proposed that, in parallel to excitatory mechanisms, inhibitory mechanisms may be actively suppressing motor output during motor imagery. These theories are verbal in nature, with well-known limitations. Here, we describe a toy-model of the inhibitory mechanisms thought to be at play during motor imagery to start disentangling predictions from competing hypotheses.

Neuromuscular effects suggest that imagery engages motor components directly - a commentary on Frank et al. (2023)

Not applicable.

Imagery practice of motor skills without conscious awareness?: a commentary to Frank et al

Modifications of imagined sensory consequences will not benefit overt performance when they cannot be transformed into motor outflow that produces them. With physical practice, the acquisition of internal models of motor transformations is largely based on prediction errors that are absent in imagery practice. What can imagery practice nevertheless contribute to transformation learning? Explicit, strategic adjustments to novel transformations should be possible. This appears less likely for implicit adjustments. Are there variants of imagery practice that can produce adjustments without conscious awareness of the transformation and/or the resultant movement changes?

The complex interplay between perception, cognition, and action: a commentary on Bach et al. 2022

Bach (Psychological Research 2022, https://doi.org/10.1007/s00426-022-01773-w ) offer a re-conceptualisation of motor imagery, influenced by older ideas of ideomotor action and formulated in terms of action effects rather than motor output. We share the view of an essential role of action effect in action planning and motor imagery processes, but we challenge the claim that motor imagery is non-motoric in nature. In the present article, we critically review some of Bach et al.'s proposed ideas and pose questions of whether effect and motor processes are functionally separable, and if not, what mechanisms underlie motor imagery and what terminology best captures its function.

Potential benefits of synchronous action observation and motor imagery: a commentary on Eaves et al. 2022

In a recent Psychological Research article, Eaves et al. (2022) review the literature on how motor imagery (MI) practice combined with action observation (AO) enhances motor performance. The authors propose that the synchronous form of AO and MI (AOMI) affords unique benefits to performance that are not possible when the two interventions are performed asynchronously. We discuss three questions raised by Eaves et al.'s review: (1) are there any clear advantages to synchronous AOMI? (2) Are there super-additive benefits to AOMI, and if so, are they unique to synchronous AOMI? (3) How might coordinative AOMI, in which people imagine complementary actions, facilitate joint actions?

Learning motor actions via imagery-perceptual or motor learning?

It is well accepted that repeatedly imagining oneself acting without any overt behavior can lead to learning. The prominent theory accounting for why imagery practice is effective, motor simulation theory, posits that imagined action and overt action are functionally equivalent, the exception being activation of the end effector. If, as motor simulation theory states, one can compile the goal, plan, motor program and outcome of an action during imagined action similar to overt action, then learning of novel skills via imagery should proceed in a manner equivalent to that of overt action. While the evidence on motor simulation theory is both plentiful and diverse, it does not explicitly account for differences in neural and behavioural findings between imagined and overt action. In this position paper, we briefly review theoretical accounts to date and present a perceptual-cognitive theory that accounts for often observed outcomes of imagery practice. We suggest that learning by way of imagery reflects perceptual-cognitive scaffolding, and that this 'perceptual' learning transfers into 'motor' learning (or not) depending on various factors. Based on this theory, we characterize consistently reported learning effects that occur with imagery practice, against the background of well-known physical practice effects and show that perceptual-cognitive scaffolding is well-suited to explain what is being learnt during imagery practice.

A theoretical perspective on action consequences in action imagery: internal prediction as an essential mechanism to detect errors

Acting in the environment results in both intended and unintended consequences. Action consequences provide feedback about the adequacy of actions while they are in progress and when they are completed and therefore contribute to monitoring actions, facilitate error detection, and are crucial for motor learning. In action imagery, no actual action takes place, and consequently, no actual action consequences are produced. However, imagined action consequences may replace actual action consequences, serving a similar function and facilitating performance improvements akin to that occurring with actual actions. In this paper, we conceptualize action imagery as a simulation based on internal models. During that simulation, forward models predict action consequences. A comparison of predicted and intended action consequences sometimes indicates the occurrence of action errors (or deviations from optimal performance) in action imagery. We review research indicating that action errors are indeed sometimes imagined in action imagery. These results are compatible with the view that action imagery is based on motor simulation but incompatible with the view that action imagery is solely based on abstract knowledge. The outlined framework seems suitable to cover a wide range of action imagery phenomena and can explain action imagery practice effects.

Neural oscillations guiding action during effects imagery

Goal-directed acting requires the integration of sensory information but can also be performed without direct sensory input. Examples of this can be found in sports and can be conceptualized by feedforward processes. There is, however, still a lack of understanding of the temporal neural dynamics and neuroanatomical structures involved in such processes. In the current study, we used EEG beamforming methods and examined 37 healthy participants in two well-controlled experiments varying the necessity of anticipatory processes during goal-directed action. We found that alpha and beta activity in the medial and posterior cingulate cortex enabled feedforward predictions about the position of an object based on the latest sensorimotor state. On this basis, theta band activity seems more related to sensorimotor representations, while beta band activity would be more involved in setting up the structure of the neural representations themselves. Alpha band activity in sensory cortices reflects an intensified gating of the anticipated perceptual consequences of the to-be-executed action. Together, the findings indicate that goal-directed acting through the anticipation of the predicted state of an effector is based on accompanying processes in multiple frequency bands in midcingulate and sensory brain regions.

The effect of action observation and motor imagery on jumping and perceived performance

Introduction

Action observation (AO) and motor imagery (MI) are cognitive processes that involve mentally rehearsing and simulating movements without physically performing them. However, the need for the evidence to support influence of imagery on performance is increasing. This study aims to investigate the impact of combining motor imagery with action observation on athletes' performance and performance perception.

Method

Using a pre-test post-test design with a factorial setup, participants were randomly assigned to experimental and control groups. A pre-research power analysis determined the sample size, resulting in 21 voluntary participants (10 male). Opto Jump device recorded drop jump performance measurements, while participants predicted their performance post-motor imagery and action observation practices. The experimental group underwent an 8-week AOMI intervention program, involving 24-minute motor imagery sessions during video observation thrice weekly. Post-test measurements were taken after the intervention.

Results

Results indicated no significant performance increase in the experimental group post-intervention, yet the group showed enhanced performance estimation following the video observation, but not in motor imagery condition. Conversely, this improvement was absent in the control group.

Discussion

Although AOMI intervention didn't enhance physical performance, it has positively affected athletes' perception toward their performance. The findings are discussed in relation to existing literature.

The Effect of Motor Imagery Practice on an Aiming Task with Attentional Focus Cues

When one directs their attention to an intended effect (external focus of attention, EFOA), motor performance is generally better than when one directs their attention to their own body movements (internal focus of attention, IFOA). However, the effect of attentional focus is unclear when a skill is practiced through motor imagery (MI) in the absence of physical trials. Participants (N = 30, M = 22.33 yrs, SD = 2.69) in the present study completed three physical trials of a reciprocal aiming task before and (24-h) after MI practice. During MI practice, the EFOA (n = 15) and IFOA (n = 15) groups mentally practiced the task with no physical practice with EFOA-MI or IFOA-MI, respectively, for three consecutive days. Our results showed that both groups significantly improved in accuracy (F1,28 = 6.49, p = .017), supporting the benefit of MI in motor skill acquisition. However, a significant effect of attentional focus was not observed (F1.,28 = 0.445, p = 0.51). We discussed two potential explanations: EFOA/IFOA requires physical trials to affect performance, or individuals must use both EFOA and IFOA in the process of creating imagery of the environment and movements, which may obscure the effect of EFOA and IFOA.

Association between visuo-spatial working memory and gait motor imagery

Although motor imagery and working memory (WM) appear to be closely linked, no previous studies have demonstrated direct evidence for the relationship between motor imagery and WM abilities. This study investigated the association between WM and gait motor imagery and focused on the individual differences in young adults. This study included 33 participants (mean age: 22.2 ± 0.9 years). We used two methods to measure the ability of different WM domains: verbal and visuo-spatial WM. Gait motor imagery accuracy was assessed via the mental chronometry paradigm. We measured the times participants took to complete an actual and imagined walk along a 5 m walkway, with three different path widths. The linear mixed effects model analysis revealed that visuo-spatial WM ability was a significant predictor of the accuracy of gait motor imagery, but not of verbal WM ability. Specifically, individuals with lower visuo-spatial WM ability demonstrated more inaccuracies in the difficult path-width conditions. However, gait motor imagery was not as accurate as actual walking even in the easiest path width or in participants with high visuo-spatial WM ability. Further, visuo-spatial WM ability was significantly correlated with mental walking but not with actual walking. These results suggest that visuo-spatial WM is related to motor imagery rather than actual movement.

Movement Representation Strategies as a Tool for Educational Innovation in Physiotherapy Students: A Randomized Single-Blind Controlled-Pilot Trial

Physiotherapy has a strictly theoretical body of knowledge, but for the most part, the physiotherapist's learning is practical. The practical part is fundamental to acquire clinical skills that the physiotherapist will later use in professional practice. The main aim of this study was to assess the effectiveness of movement representation strategies (MRS) in the improvement of manual skills of physiotherapy students as an educational innovation strategy. We randomly assigned 30 participants to an action observation practice (AOP), motor imagery practice (MIP), or sham observation (SO) group. A high velocity, low amplitude lumbar manipulation technique that is widely used in clinical physiotherapy practice was taught in one session. The primary outcomes were required time and test score. The secondary outcomes were perceived mental fatigue and perceived difficulty for learning. The outcomes were assessed preintervention and immediately after the intervention (postintervention). The main results showed that both AOP and MIP improved the total time required and the test score, as well as entailed less perceived difficulty for learning. However, both strategies showed a higher level of mental fatigue after the intervention, which was higher in the MIP group. Based on the results obtained, it seems that the application of MRS promotes greater learning of manual motor tasks in physiotherapy students and could be used as educational innovation strategies.