Human Motor System Research Articles

Biological motion and animacy belief induce similar effects on involuntary shifts of attention.

Biological motion is salient to the human visual and motor systems and may be intrinsic to the perception of animacy. Evidence for the salience of visual stimuli moving with trajectories consistent with biological motion comes from studies showing that such stimuli can trigger shifts of attention in the direction of that motion. The present study was conducted to determine whether or not top-down beliefs about animacy can modify the salience of a nonbiologically moving stimulus to the visuomotor system. A nonpredictive cuing task was used in which a white dot moved from a central location toward a left- or right-sided target placeholder. The target randomly appeared at either location 200, 600, or 1,300 ms after the motion onset. Five groups of participants experienced different stimulus conditions: (1) biological motion, (2) inverted biological motion, (3) nonbiological motion, (4) animacy belief (paired with nonbiological motion), and (5) computer-generated belief (paired with nonbiological motion). Analysis of response times revealed that the motion in the biological motion and animacy belief groups, but not in the inverted and nonbiological motion groups, affected processing of the target information. These findings indicate that biological motion is salient to the visual system and that top-down beliefs regarding the animacy of the stimulus can tune the visual and motor systems to increase the salience of nonbiological motion.

Interpreting and responding to ambiguous natural images in spider phobia

Background and objectivesThe fast detection of and response to threatening stimuli is an important task of the human visual and motor systems, and is especially challenging when stimuli are ambiguous. This study investigates the perception, evaluation and fast response to ambiguous natural spider stimuli in spider-fearful and non-anxious participants. MethodsStimuli were created by gradually morphing natural images of spiders and non-spiders (a crab, a starfish, a bunch of keys, and a flower). In Study 1, participants rated the images on perceptual and emotional dimensions and responded to them in a response priming task to measure rapid information processing. In Study 2, results were validated and extended in a different paradigm by using a go/no-go task. ResultsAs expected, spider-fearful participants showed an interpretative bias for ambiguous stimuli (i.e., perceived them as more similar to spiders) and rated spider(-like) stimuli as more unpleasant, arousing, and disgusting. In Study 1, spider stimuli were preferentially processed in spider-fearful participants as observed in faster responses to spider targets–however, responses were not different to comparison participants for ambiguous stimuli. Study 2 suggests that this finding can be explained by differences in stimulus duration. LimitationsNo participants with positive attitudes towards spiders or a second fearful comparison group were included. ConclusionsWe suggest that these findings can be explained by the nature of the applied tasks that tap into early phases of visual processing, thereby relying on feedforward-mediated low-spatial-frequency information extracted via the fast, subcortical path to the amygdala.

Precentral degeneration and cerebellar compensation in amyotrophic lateral sclerosis: A multimodal MRI analysis.

Amyotrophic lateral sclerosis (ALS) is a progressive and intractable neurodegenerative disease of human motor system characterized by progressive muscular weakness and atrophy. A considerable body of research has demonstrated significant structural and functional abnormalities of the primary motor cortex in patients with ALS. In contrast, much less attention has been paid to the abnormalities of cerebellum in this disease. Using multimodal magnetic resonance imagining data of 60 patients with ALS and 60 healthy controls, we examined changes in gray matter volume (GMV), white matter (WM) fractional anisotropy (FA), and functional connectivity (FC) in patients with ALS. Compared with healthy controls, patients with ALS showed decreased GMV in the left precentral gyrus and increased GMV in bilateral cerebellum, decreased FA in the left corticospinal tract and body of corpus callosum, and decreased FC in multiple brain regions, involving bilateral postcentral gyrus, precentral gyrus and cerebellum anterior lobe, among others. Meanwhile, we found significant intermodal correlations among GMV of left precentral gyrus, FA of altered WM tracts, and FC of left precentral gyrus, and that WM microstructural alterations seem to play important roles in mediating the relationship between GMV and FC of the precentral gyrus, as well as the relationship between GMVs of the precentral gyrus and cerebellum. These findings provided evidence for the precentral degeneration and cerebellar compensation in ALS, and the involvement of WM alterations in mediating the relationship between pathologies of the primary motor cortex and cerebellum, which may contribute to a better understanding of the pathophysiology of ALS.

Assessment of human motoneuron excitability during functional motor tasks

Detailed investigations of the human motor system are often performed under isometric conditions, although few real‐world activities incorporate isometric contractions. Because of their one‐to‐one relationship with muscle fibers and high safety factor, spinal motoneurons are the only cells in the central nervous system from which firing patterns can be readily accessed in humans. Recent advances in motor unit action potential (MUAP) decomposition techniques using high‐density surface array electrodes allow large numbers of MUAPs to be discriminated relatively non‐invasively. The activity of multiple motor units can allow for the quantification of motoneuron excitability. For example, the paired motor unit analysis technique compares the onset and offset of a high‐threshold motor unit with respect to a low‐threshold unit and quantifies discharge rate hysteresis (ΔF), which is proportional to the intrinsic excitability of the spinal motoneuron. During movements where joint torque measurements are not feasible (i.e. unconstrained by the dynamometer) electromyography (EMG) is often used as a surrogate for the level of muscle activity. However, whether activity level feedback provided by EMG measurements or torque during voluntary contractions elicits similar ΔF values is unknown. We hypothesized that during voluntary isometric ramp contractions, ΔF is similar whether feedback is provided with a torque signal or conditioned EMG. We further hypothesized that standing postural adjustments using EMG feedback in unconstrained conditions will produce similar ΔF values to those calculated during the isometric ramps. We expected that although the mean values across conditions will be similar, the inter‐subject coefficient of variation of ΔF will be greater in the less constrained condition. Accordingly, surface EMG using high‐density array electrodes was collected from five subjects under three conditions: 1) seated in a dynamometer in the isometric mode with activity level feedback provided by the torque (ISO‐TOR), 2) in the isometric dynamometer with feedback provided by EMG (ISO‐EMG), and 3) during postural adjustments while standing freely with feedback provided by EMG (POS‐EMG). In agreement with our hypothesis, we found that ΔF values across all three conditions were similar. In the ISO‐TOR and ISO‐EMG conditions, ΔF was 2.70 ± 0.70 imp/s and 3.40 ± 0.75 imp/s, respectively; during POS‐EMG it was 3.08 ± 0.73 imp/s (all n = 5, mean ± SE). Contrary to our expectations, the coefficient of variation was not greater in the unconstrained standing condition. These results demonstrate that real‐time EMG feedback is sufficiently similar to torque feedback during both isometric and near‐isometric, unconstrained contractions, suggesting that detailed investigations of motor unit activity may be expanded to more functional movements.Support or Funding InformationFunded by R01 NS098509‐01 and T32 HD007418‐27This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Prefrontal-Premotor Pathways and Motor Output in Well-Recovered Stroke Patients.

Structural brain imaging has continuously furthered our knowledge how different pathways of the human motor system contribute to residual motor output in stroke patients. Tract-related microstructure of pathways between primary and premotor areas has been found to critically influence motor output. The motor network is not restricted in connectivity to motor and premotor areas but these brain regions are densely interconnected with prefrontal regions such as the dorsolateral (DLPFC) and ventrolateral (VLPFC) prefrontal cortex. So far, the available data about the topography of such direct pathways and their microstructural properties in humans are sparse. To what extent prefrontal-premotor connections might also relate to residual motor outcome after stroke is still an open question. The present study was designed to address this issue of structural connectivity of prefrontal-premotor pathways in 26 healthy, older participants (66 ± 10 years old, 15 male) and 30 well-recovered chronic stroke patients (64 ± 10 years old, 21 males). Probabilistic tractography was used to reconstruct direct fiber tracts between DLPFC and VLPFC and three premotor areas (dorsal and ventral premotor cortex and the supplementary motor area). Direct connections between DLPFC/VLPFC and the primary motor cortex were also tested. Tract-related microstructure was estimated for each specific tract by means of fractional anisotropy and alternative diffusion metrics. These measures were compared between the groups and related to residual motor outcome in the stroke patients. Direct prefrontal-premotor trajectories were successfully traceable in both groups. Similar in gross anatomic topography, stroke patients presented only marginal microstructural alterations of these tracts, predominantly of the affected hemisphere. However, there was no clear evidence for a significant association between tract-related microstructure of prefrontal-premotor connections and residual motor functions in the present group of well-recovered stroke patients. Direct prefrontal-motor connections between DLPFC/VLPFC and the primary motor cortex could not be reconstructed in the present healthy participants and stroke patients.

Cognitive Load Theory and Human Movement: Towards an Integrated Model of Working Memory

Cognitive load theory (CLT) applies what is known about human cognitive architecture to the study of learning and instruction, to generate insights into the characteristics and conditions of effective instruction and learning. Recent developments in CLT suggest that the human motor system plays an important role in cognition and learning; however, it is unclear whether models of working memory (WM) that are typically espoused by CLT researchers can reconcile these novel findings. For instance, often-cited WM models envision separate information processing systems—such as Baddeley and Hitch’s (1974) multicomponent model of WM—as a means to interpret modality-specific findings, although possible interactions with the human motor system remain under-explained. In this article, we examine the viability of these models to theoretically integrate recent research findings regarding the human motor system, as well as their ability to explain established CLT effects and other findings. We argue, it is important to explore alternate models of WM that focus on a single and integrated control of attention system that is applied to visual, phonological, embodied, and other sensory and nonsensory information. An integrated model such as this may better account for individual differences in experience and expertise and, parsimoniously, explain both recent and historical CLT findings across domains. To advance this aim, we propose an integrated model of WM that envisions a common and finite attentional resource that can be distributed across multiple modalities. How attention is mobilized and distributed across domains is interdependent, co-reinforcing, and ever-changing based on learners’ prior experience and their immediate cognitive demands. As a consequence, the distribution of attentional focus and WM resources will vary across individuals and tasks, depending on the nature of the specific task being performed; the neurological, developmental, and experiential abilities of the individual; and the current availability of internal and external cognitive resources.

Starting and stopping movement by the primate brain.

We review the current knowledge about the part that motor cortex plays in the preparation and generation of movement, and we discuss the idea that corticospinal neurons, and particularly those with cortico-motoneuronal connections, act as ‘command’ neurons for skilled reach-to-grasp movements in the primate. We also review the increasing evidence that it is active during processes such as action observation and motor imagery. This leads to a discussion about how movement is inhibited and stopped, and the role in these for disfacilitation of the corticospinal output. We highlight the importance of the non-human primate as a model for the human motor system. Finally, we discuss the insights that recent research into the monkey motor system has provided for translational approaches to neurological diseases such as stroke, spinal injury and motor neuron disease.

Neural activity related to volitional regulation of cortical excitability.

To date there exists no reliable method to non-invasively upregulate or downregulate the state of the resting human motor system over a large dynamic range. Here we show that an operant conditioning paradigm which provides neurofeedback of the size of motor evoked potentials (MEPs) in response to transcranial magnetic stimulation (TMS), enables participants to self-modulate their own brain state. Following training, participants were able to robustly increase (by 83.8%) and decrease (by 30.6%) their MEP amplitudes. This volitional up-versus down-regulation of corticomotor excitability caused an increase of late-cortical disinhibition (LCD), a TMS derived read-out of presynaptic GABAB disinhibition, which was accompanied by an increase of gamma and a decrease of alpha oscillations in the trained hemisphere. This approach paves the way for future investigations into how altered brain state influences motor neurophysiology and recovery of function in a neurorehabilitation context.

Self-powered robots to reduce motor slacking during upper-extremity rehabilitation: a proof of concept study.

Robotic rehabilitation is a highly promising approach to recover lost functions after stroke or other neurological disorders. Unfortunately, robotic rehabilitation currently suffers from "motor slacking", a phenomenon in which the human motor system reduces muscle activation levels and movement excursions, ostensibly to minimize metabolic- and movement-related costs. Consequently, the patient remains passive and is not fully engaged during therapy. To overcome this limitation, we envision a new class of body-powered robots and hypothesize that motor slacking could be reduced if individuals must provide the power to move their impaired limbs via their own body (i.e., through the motion of a healthy limb). To test whether a body-powered exoskeleton (i.e. robot) could reduce motor slacking during robotic training. We developed a body-powered robot that mechanically coupled the motions of the user's elbow joints. We tested this passive robot in two groups of subjects (stroke and able-bodied) during four exercise conditions in which we controlled whether the robotic device was powered by the subject or by the experimenter, and whether the subject's driven arm was engaged or at rest. Motor slacking was quantified by computing the muscle activation changes of the elbow flexor and extensor muscles using surface electromyography. Subjects had higher levels of muscle activation in their driven arm during self-powered conditions compared to externally-powered conditions. Most notably, subjects unintentionally activated their driven arm even when explicitly told to relax when the device was self-powered. This behavior was persistent throughout the trial and did not wane after the initiation of the trial. Our findings provide novel evidence indicating that motor slacking can be reduced by self-powered robots; thus demonstrating promise for rehabilitation of impaired subjects using this new class of wearable system. The results also serve as a foundation to develop more sophisticated body-powered robots (e.g., with controllable transmissions) for rehabilitation purposes.

From One to Many: Representing Not Only Actions, but Interactions in the Brain

Observing others is a pervasive way of learning about the social world, but little is known about the neural correlates of observing more than one individual. A recent neuroimaging study demonstrates that activity in the human motor system tracks multiple actions and that anterior cingulate cortex is involved to monitor motor conflict.

The role of the motor system in action understanding and communication: Evidence from human infants and non-human primates.

There is growing evidence that activation of the motor system during observation of actions, a phenomenon first observed in non-human primates, underlies action understanding and even communication. This review (a) examines the evidence on motor system activity as an underlying neural correlate of action understanding; (b) reviews the theoretical and empirical work linking action understanding and the development of communication, with a specific focus on the role that gestures play as an intermediary; and (c) discusses the research on and existing opportunities for understanding the link between the motor system and communication in both humans and non-human primates, through the lens of action perception. Bringing together findings and perspectives from developmental social cognition in both humans and non-human primates and applying recent neuroscientific perspectives will help to elucidate the processes underlying the ability to understand and communicate with others.

Intact automatic motor inhibition in attention deficit hyperactivity disorder

Hyperactivity and impulsivity are defining symptoms of attention-deficit hyperactivity disorder (ADHD), next to inattention. Hyperactive and impulsive behavior in ADHD is often thought to result from a deficit in inhibitory motor control. However, testing for such a deficit is complicated by coexisting deficits in ADHD, specifically an impairment in maintaining task set, e.g., due to inattention. Typical inhibition paradigms, such as Stop-signal, Go/NoGo or Flanker paradigms, are susceptible to a fundamental confound between inhibition and inattention because inhibition is an explicit goal in these tasks. We eliminate this confound by studying the negative compatibility effect (NCE), reflecting a core inhibitory function in the human motor system which, in healthy individuals, inhibits movements automatically, i.e., without deliberation or even conscious awareness. Our behavioral analysis, including Bayesian model comparison, as well as the time-course of the lateralized readiness potential (LRP), consistently show that this function is intact in children with ADHD compared to healthy controls, independent of the presence or absence of prominent hyperactive-impulsive symptoms. We conclude that hyperactivity and impulsivity in ADHD do not result from a low-level deficit in motor inhibition.

Inhibitory and facilitatory connections from dorsolateral prefrontal to primary motor cortex in healthy humans at rest—An rTMS study

BackgroundThe human motor system consists of several divisions in the frontal lobes. The physiological function of projections from the dorsolateral prefrontal cortex (DLPFC) to the primary motor cortex (M1) remains elusive. Here, we introduce theta burst stimulation (TBS)-based protocols to target inhibitory and facilitatory connections in the DLPFC-M1 network. MethodsIntermittent and continuous TBS with 600 pulses (iTBS600/cTBS600) were applied to the left DLPFC. Resting motor threshold (RMT), motor-evoked potential (MEP), and short-interval intracortical inhibition (SICI) were measured with transcranial magnetic stimulation to the ipsilateral M1. ResultsiTBS600 to the DLPFC decreased MEP amplitude in M1. Conversely, cTBS600 to the DLPFC increased MEP amplitude in M1. The peak decrease in MEP amplitude after iTBS600 was negatively correlated with the peak increase in MEP amplitude after cTBS600. There were no significant effects in the control group with the sham stimulation. DiscussionThese results provide insight into the regulation of inhibitory and facilitatory balance from the local DLPFC to M1. TBS modulation in one brain region will induce interactions within other remote cortical areas. Our results enable better understanding of how cognitive resources are allocated to achieve optimal control of motor output.

Accuracy of Motor Error Predictions for Different Sensory Signals.

Detecting and evaluating errors in action execution is essential for learning. Through complex interactions of the inverse and the forward model, the human motor system can predict and subsequently adjust ongoing or subsequent actions. Inputs to such a prediction are efferent and afferent signals from various sources. The aim of the current study was to examine the impact of visual as well as a combination of efferent and proprioceptive input signals to error prediction in a complex motor task. Predicting motor errors has been shown to be correlated with a neural signal known as the error-related negativity (Ne/ERN). Here, we tested how the Ne/ERN amplitude was modulated by the availability of different sensory signals in a semi-virtual throwing task where the action outcome (hit or miss of the target) was temporally delayed relative to movement execution allowing participants to form predictions about the outcome prior to the availability of knowledge of results. 19 participants practiced the task and electroencephalogram was recorded in two test conditions. In the Visual condition, participants received only visual input by passively observing the throwing movement. In the EffProp condition, participants actively executed the task while visual information about the real and the virtual effector was occluded. Hence, only efferent and proprioceptive signals were available. Results show a significant modulation of the Ne/ERN in the Visual condition while no effect could be observed in the EffProp condition. In addition, amplitudes of the feedback-related negativity in response to the actual outcome feedback were found to be inversely related to the Ne/ERN amplitudes. Our findings indicate that error prediction is modulated by the availability of input signals to the forward model. The observed amplitudes were found to be attenuated in comparison to previous studies, in which all efferent and sensory inputs were present. Furthermore, we assume that visual signals are weighted higher than proprioceptive signals, at least in goal-oriented tasks with visual targets.

In vitro biomimetic HPLC and in vivo characterisation of GM6, an endogenous regulator peptide drug candidate for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an idiopathic, fatal neurodegenerative disease of the human motor system. Subunits of the 33-amino acid containing motorneurontrophic factor (MNTF) have been investigated and GM6 has been found as a potential peptide therapeutic for ALS. This linear peptide drug candidate has been characterized by HPLC based physicochemical and biomimetic measurements to estimate its in vivo distribution behavior and to estimate its cell penetration and brain to plasma concentration ratio. The free tissue concentration vs time profile has been estimated using the measured physicochemical and biomimetic properties of the intact GM6 molecules and its microsomal stability. The in vitro and in vivo measurements supported the estimated in vivo distribution behavior of GM6.

Motor Intention/Intentionality and Associationism - A conceptual review.

Motor intention/intentionality (MI) has been investigated from many different angles. Some researchers focus on the purely physical and mechanical aspects of the human motor system, while others emphasize the subjectivity involved in intentionality. While bridging this seemingly dualistic gap between the two concepts ought to be the researcher's' main task, different schools of thought have instead specialized in stressing one (objective) or the other (subjective) part of this construct. Thus, we find everything from neuroscientific to phenomenologically inspired approaches to MI. The purpose of this article is to review the literature regarding these different approaches to the MI construct. In reviewing the literature, we introduce a broadened conception of associationism. In organizing our data in relation to the laws of association, a lack of methodology clearly manifests itself. Hence, 123 articles out of 143 meet the criteria of our definition of associationism. It seems that this old doctrine sneaks in to a big part of the research rather implicitly through a lack of methodology. To shed light on how this happens in the 123 articles, we develop a continuum to show to which extend associationism operates on a transcendent or substantial level in each article. We find only very few articles that seem to try to gap the bridge between motor and intention/intentionality, and thus we suggest that future MI research reintroduce methodological debates concerning the conceptual character of this construct.

Gait pattern discrimination of ALS patients using classi cation methods

Amyotrophic lateral sclerosis (ALS) is a mortal and idiopathic neurodegenerative disturbance of the human motor system. The disturbances of locomotion due to neurodegenerative diseases (NDDs) consisting of ALS, Parkinson disease (PD), and Huntington disease (HD) cause some abnormal fluctuations in gait signals. The investigation into gait patterns of NDDs provides significant information in order to develop new biomedical diagnosis devices. The main objective of this study is to evaluate the best discrimination method of ALS among control subjects (Co.), PD patients, and HD patients. The D2, D4, D5, and D6 detailed components, which were determined as critical features extracted from gait signals using discrete wavelet transform analysis in our previous study, are used as the inputs of all classification methods of the present study. Multilayer perceptron neural networks (MLPNNs), radial basis function neural networks, generalized regression neural networks, support vector machines, and decision tree classifiers are evaluated in this study. The MLPNN classifier, for which the average accuracy percentage is calculated as 92.09{\%}, is evaluated as the most accomplished method. The best leave-one-out cross-validation (LOOCV) score as testing{\%} (all-training-all-testing{\%}) in MLPNN is calculated as 96.55{\%} (99.76{\%}) for ALS vs. Co. discrimination. Other LOOCV scores with MLPNNs are calculated as 82.14{\%} (99.36{\%}) for ALS vs. PD, 78.79{\%} (99.17{\%}) for ALS vs. HD, 83.33{\%} (98.87{\%}) for ALS vs. HD+PD, and 82.81{\%} (99.00{\%}) for ALS vs. HD+PD+Co., respectively. Consequently, this study proposes a new classification method based on MLPNNs to discriminate ALS among other NDDs and Co. after comparing the results.

Sequential Articulated Motion Reconstruction from a Monocular Image Sequence

In this article, we present a sequential approach for articulated motion estimation from a 2D skeleton sequence. This is a challenging task due to the complexity of human movements and the inherent depth ambiguities. The proposed approach models the human movement on a kinematic manifold with the tangent bundle, which is a natural geometrical representation of articulated motion. Combined with a second-order stochastic dynamic model based on the Markov hypothesis, we generalize the Extended Rauch Tung Striebel smoother to a Riemannian manifold to simulate the process of human movement. The human motor system might violate the Markov hypothesis when the human body is subject to external forces, and therefore a refinement stage is introduced to correct the estimation error. Specifically, the current estimation is refined in a feasible solution region consisting of a set of local estimations. This region is called a simplex, in which each element can be represented by a convex hull of all ingredients. We have proved that the refinement problem can be converted into a convex optimization problem with the simplicial constraint. Since the proposed formulation conforms to the principles of kinematic and spatio-temporal continuity of articulated motion, the reconstruction ambiguity can be alleviated essentially. The performance of the proposed algorithm is conducted on multiple synthetic sequences from the CMU and the HDM05 MoCap databases. The results show that, without requiring any training data, the proposed approach achieves greater accuracy over state-of-the-art baselines. Furthermore, the proposed approach outperforms two baselines on real sequences from the Human3.6m MoCap database.

Learning alternative movement coordination patterns using reinforcement feedback

One of the characteristic features of the human motor system is redundancy-i.e., the ability to achieve a given task outcome using multiple coordination patterns. However, once participants settle on using a specific coordination pattern, the process of learning to use a new alternative coordination pattern to perform the same task is still poorly understood. Here, using two experiments, we examined this process of how participants shift from one coordination pattern to another using different reinforcement schedules. Participants performed a virtual reaching task, where they moved a cursor to different targets positioned on the screen. Our goal was to make participants use a coordination pattern with greater trunk motion, and to this end, we provided reinforcement by making the cursor disappear if the trunk motion during the reach did not cross a specified threshold value. In Experiment 1, we compared two reinforcement schedules in two groups of participants-an abrupt group, where the threshold was introduced immediately at the beginning of practice; and a gradual group, where the threshold was introduced gradually with practice. Results showed that both abrupt and gradual groups were effective in shifting their coordination patterns to involve greater trunk motion, but the abrupt group showed greater retention when the reinforcement was removed. In Experiment 2, we examined the basis of this advantage in the abrupt group using two additional control groups. Results showed that the advantage of the abrupt group was because of a greater number of practice trials with the desired coordination pattern. Overall, these results show that reinforcement can be successfully used to shift coordination patterns, which has potential in the rehabilitation of movement disorders.

From goals to muscles: motor familiarity shapes the representation of action-related sounds in the human motor system

ABSTRACTNumerous studies corroborated the idea that the sound of familiar motor acts triggers a muscle-specific replica of the perceived actions in the listener’s brain. We recently contradicted this conclusion by demonstrating that the representation of newly-learned action-related sounds is not somatotopically organised but rather it corresponds to the goal a particular action aims to achieve. In the present study, we aimed at reconciling these results. We measured MEPs to TMS as an index of the functional correspondence between the sensory stimulation and the activity in the listener’s motor cortex. Participants heard two tones of different pitch, void of previous motor meaning, before and after an acquisition phase in which they generated them by performing 400 free-choice button presses. We then disentangled the representation of the action goal (button–tone association) from the somatotopic (muscle–tone) association by reversing the muscle–button contingencies. Our result supports the hypothesis that the neuronal representations of action-related sounds depends on motor familiarity: perceptuomotor representations of newly-learned actions are muscle–independent and correspond to the button–tone contingencies, whilst longer-term practice results in representations that rely on lower-level intrinsic parameters associated with the kinematics of specific movements.