Motor Error Research Articles

A novel dopamine D3R agonist SK609 with norepinephrine transporter inhibition promotes improvement in cognitive task performance in rodent and non-human primate models of Parkinson's disease

Mild cognitive impairment is present in a number of neurodegenerative disorders including Parkinson's disease (PD). Mild cognitive impairment in PD (PD-MCI) often manifests as deficits in executive functioning, attention, and spatial and working memory. Clinical studies have suggested that the development of mild cognitive impairment may be an early symptom of PD and may even precede the onset of motor impairment by several years. Dysfunction in several neurotransmitter systems, including dopamine (DA), norepinephrine (NE), may be involved in PD-MCI, making it difficult to treat pharmacologically. In addition, many agents used to treat motor impairment in PD may exacerbate cognitive impairment. Thus, there is a significant unmet need to develop therapeutics that can treat both motor and cognitive impairments in PD. We have recently developed SK609, a selective, G-protein biased signaling agonist of dopamine D3 receptors. SK609 was successfully used to treat motor impairment and reduce levodopa-induced dyskinesia in a rodent model of PD. Further characterization of SK609 suggested that it is a selective norepinephrine transporter (NET) inhibitor with the ability to increase both DA and NE levels in the prefrontal cortex. Pharmacokinetic analysis of SK609 under systemic administration demonstrated 98% oral bioavailability and high brain distribution in striatum, hippocampus and prefrontal cortex. To evaluate the effects of SK609 on cognitive deficits of potential relevance to PD-MCI, we used unilateral 6-hydroxydopamine (6-OHDA) lesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cynomolgus macaques, with deficits in performance in a sustained attention and an object retrieval task, respectively. SK609 dose dependently improved the performance of 6-OHDA-lesioned rats, with peak performance achieved using a 4 mg/kg dose. This improvement was predominantly due to a significant reduction in the number of misses and false alarm errors, contributing to an increase in sustained attention. In MPTP-lesioned monkeys, this same dose also improved performance in an object retrieval task, significantly reducing cognitive errors (barrier reaches) and motor errors (fine motor dexterity problems). These data demonstrate that SK609 with its unique pharmacological effects on modulating both DA and NE can ameliorate cognitive impairment in PD models and may provide a therapeutic option to treat both motor and cognitive impairment in PD patients.

Pre-movement changes in sensorimotor beta oscillations predict motor adaptation drive

Beta frequency oscillations in scalp electroencephalography (EEG) recordings over the primary motor cortex have been associated with the preparation and execution of voluntary movements. Here, we test whether changes in beta frequency are related to the preparation of adapted movements in human, and whether such effects generalise to other species (cat). Eleven healthy adult humans performed a joystick visuomotor adaptation task. Beta (15–25 Hz) scalp EEG signals recorded over the motor cortex during a pre-movement preparatory phase were, on average, significantly reduced in amplitude during early adaptation trials compared to baseline, late adaptation, or aftereffect trials. The changes in beta were not related to measurements of reaction time or reach duration. We also recorded local field potential (LFP) activity within the primary motor cortex of three cats during a prism visuomotor adaptation task. Analysis of these signals revealed similar reductions in motor cortical LFP beta frequencies during early adaptation. This effect was present when controlling for any influence of the reaction time and reach duration. Overall, the results are consistent with a reduction in pre-movement beta oscillations predicting an increase in adaptive drive in upcoming task performance when motor errors are largest in magnitude and the rate of adaptation is greatest.

Triggering microsaccades by foveal motor error is sufficient to modulate peripheral visual sensitivity: neural and perceptual evidence

Visual processing is frequently interspersed with saccades, which are associated with strong peri-movement changes in neural and perceptual sensitivity. With fixed gaze, for controlled experiments on processes like covert attention, microsaccades still occur. During the past two decades, it became clear that microsaccades are not random (Hafed and Clark, 2002; Engbert and Kliegl, 2003), but instead exhibit predictable correlations with enhanced or decreased peripheral visual sensitivity (in multiple brain areas) and perception. These time-locked changes appear at eccentricities 1-2 orders of magnitude larger than the eye movement endpoints themselves. However, it remains unclear whether it is microsaccades, perhaps through their motor preparatory activity, that causally influence visual sensitivity, or whether visual sensitivity is itself modulated independently of microsaccades, maybe through oscillatory brain-state fluctuations; in this case, it is such modulations that “leak” into the motor system and trigger microsaccades. Here, motivated by (Hafed and Clark, 2002), in which no attentional effects were present in the absence of microsaccades, we tested the former hypothesis. We used real-time retinal image stabilization to introduce foveal motor errors at fixation (~0.06 deg) and causally drive microsaccades in an experimentally-controlled direction. We then presented peripheral (>5 deg) visual stimuli congruent or incongruent with microsaccade direction and recorded monkey superior colliculus (SC) activity. We found enhanced visual sensitivity and faster reaction times for microsaccade-congruent stimuli as a result of causally-generated microsaccades. In humans, we adapted a known task for pre-saccadic perceptual sensitivity (Rolfs & Carrasco, 2012) for microsaccades: subjects fixated, and we shifted the fixation spot by ~0.18 deg right or left to trigger microsaccades; the actual perceptual task (contrast comparison) was done for stimuli at 7 deg. Peripheral contrast sensitivity was enhanced before experimentally-manipulated microsaccades congruent with stimulus location, consistent with the neurophysiological results. Thus, foveal motor activity is sufficient to influence peripheral visual sensitivity.

Way of Assessing an Athlete’s Upright Posture Control while Performing Tracking Movements

Numerical modeling is performed of movement control processes in higher regions of the human brain during the planning and execution of voluntary tracking movements, based on the internal model hypothesis. Such measures as a Kalman filter, linear–quadratic estimator, and linear–quadratic regulator are used. A way of determining moments of the activation of controls is proposed, based on an analysis of the trajectory of tracking movements. Different indicators of the quality of executing tracking movements, including energy expenditure, stability, contributions from motor errors, planning, and execution, are estimated numerically. Real experimental data is obtained in tests of athletes on the national teams of Russia. Practical application of the considered measures to training is shown.

Multi-Dimensional, Short-Timescale Quantification of Parkinson's Disease and Essential Tremor Motor Dysfunction.

Introduction: Parkinson's disease (PD) is a progressive movement disorder characterized by heterogenous motor dysfunction with fluctuations in severity. Objective, short-timescale characterization of this dysfunction is necessary as therapies become increasingly adaptive.Objectives: This study aims to characterize a novel, naturalistic, and goal-directed tablet-based task and complementary analysis protocol designed to characterize the motor features of PD.Methods: A total of 26 patients with PD and without deep brain stimulation (DBS), 20 control subjects, and eight patients with PD and with DBS completed the task. Eight metrics, each designed to capture an aspect of motor dysfunction in PD, were calculated from 1-second, non-overlapping epochs of the raw positional and pressure data captured during task completion. These metrics were used to generate a classifier using a support vector machine (SVM) model to produce a unifying, scalar “motor error score” (MES). The data generated from these patients with PD were compared to same-day standard clinical assessments. Additionally, these data were compared to analogous data generated from a separate group of 12 patients with essential tremor (ET) to assess the task's specificity for different movement disorders. Finally, an SVM model was generated for each of the eight patients with PD and with DBS to differentiate between their motor dysfunction in the “DBS On” and “DBS Off” stimulation states.Results: The eight metrics calculated from the raw positional and force data captured during task completion were non-redundant. MES generated by the SVM analysis protocol showed a strong correlation with MDS-UPDRS-III scores assigned by movement disorder specialists. Analysis of the relative contributions of each of the eight metrics showed a significant difference between the motor dysfunction of PD and ET. Much of this difference was attributable to the homogenous, tremor-dominant phenotype of ET motor dysfunction. Finally, in individual patients with PD with DBS, task performance and subsequent SVM classification effectively differentiated between the “DBS On” and “DBS Off” stimulation states.Conclusion: This tablet-based task and analysis protocol correlated strongly with expert clinical assessments of PD motor dysfunction. Additionally, the task showed specificity for PD when compared to ET, another common movement disorder. This specificity was driven by the relative heterogeneity of motor dysfunction of PD compared to ET. Finally, the task was able to distinguish between the “DBS On” and “DBS Off” states within single patients with PD. This task provides temporally-precise and specific information about motor dysfunction in at least two movement disorders that could feasibly correlate to neural activity.

Chronic jaw pain attenuates neural oscillations during motor-evoked pain

Motor- and pain-related processes separately induce a reduction in alpha and beta power. When movement and pain occur simultaneously but are independent of each other, the effects on alpha and beta power are additive. It is not clear whether this additive effect is evident during motor-evoked pain in individuals with chronic pain. We combined highdensity electroencephalography (EEG) with a paradigm in which motor-evoked pain was induced during a jaw force task. Participants with chronic jaw pain and pain-free controls produced jaw force at 2% and 15% of their maximum voluntary contraction. The chronic jaw pain group showed exacerbated motor-evoked pain as force amplitude increased and showed increased motor variability and motor error irrespective of force amplitude. The chronic jaw pain group had an attenuated decrease in power in alpha and lower-beta frequencies in the occipital cortex during the anticipation and experience of motor-evoked pain. Rather than being additive, motor-evoked pain attenuated the modulation of alpha and beta power, and this was most evident in occipital cortex. Our findings provide the first evidence of changes in neural oscillations in the cortex during motor-evoked jaw pain.

Determining mean and standard deviation of the strong gravity prior through simulations.

Humans expect downwards moving objects to accelerate and upwards moving objects to decelerate. These results have been interpreted as humans maintaining an internal model of gravity. We have previously suggested an interpretation of these results within a Bayesian framework of perception: earth gravity could be represented as a Strong Prior that overrules noisy sensory information (Likelihood) and therefore attracts the final percept (Posterior) very strongly. Based on this framework, we use published data from a timing task involving gravitational motion to determine the mean and the standard deviation of the Strong Earth Gravity Prior. To get its mean, we refine a model of mean timing errors we proposed in a previous paper (Jörges & López-Moliner, 2019), while expanding the range of conditions under which it yields adequate predictions of performance. This underscores our previous conclusion that the gravity prior is likely to be very close to 9.81 m/s2. To obtain the standard deviation, we identify different sources of sensory and motor variability reflected in timing errors. We then model timing responses based on quantitative assumptions about these sensory and motor errors for a range of standard deviations of the earth gravity prior, and find that a standard deviation of around 2 m/s2 makes for the best fit. This value is likely to represent an upper bound, as there are strong theoretical reasons along with supporting empirical evidence for the standard deviation of the earth gravity being lower than this value.

Rapid motor fluctuations reveal short-timescale neurophysiological biomarkers of Parkinson’s disease

Objective. Identifying neural activity biomarkers of brain disease is essential to provide objective estimates of disease burden, obtain reliable feedback regarding therapeutic efficacy, and potentially to serve as a source of control for closed-loop neuromodulation. In Parkinson’s disease (PD), microelectrode recordings (MER) are routinely performed in the basal ganglia to guide electrode implantation for deep brain stimulation (DBS). While pathologically-excessive oscillatory activity has been observed and linked to PD motor dysfunction broadly, the extent to which these signals provide quantitative information about disease expression and fluctuations, particularly at short timescales, is unknown. Furthermore, the degree to which informative signal features are similar or different across patients has not been rigorously investigated. We sought to determine the extent to which motor error in PD across patients can be decoded on a rapid timescale using spectral features of neural activity. Approach. Here, we recorded neural activity from the subthalamic nucleus (STN) of subjects with PD undergoing awake DBS surgery while they performed an objective, continuous behavioral assessment that synthesized heterogenous PD motor manifestations to generate a scalar measure of motor dysfunction at short timescales. We then leveraged natural motor performance variations as a ‘ground truth’ to identify corresponding neurophysiological biomarkers. Main results. Support vector machines using multi-spectral decoding of neural signals from the STN succeeded in tracking the degree of motor impairment at short timescales (as short as one second). Spectral power across a wide range of frequencies, beyond the classic ‘β’ oscillations, contributed to this decoding, and multi-spectral models consistently outperformed those generated using more isolated frequency bands. While generalized decoding models derived across subjects were able to estimate motor impairment, patient-specific models typically performed better. Significance. These results demonstrate that quantitative information about short-timescale PD motor dysfunction is available in STN neural activity, distributed across various patient-specific spectral components, such that an individualized approach will be critical to fully harness this information for optimal disease tracking and closed-loop neuromodulation.

The Effects Of High-altitude Mountaineering On Cognitive Function In Mountaineers: A Meta-analysis

PURPOSE: Nowadays, high altitude mountaineering is increasingly popular among different populations with a dream to challenge high-altitude exercises facilitated by the convenience of global traveling. In view of this, the authors performed a meta-analysis in the hope of finding the effects of high-altitude mountaineering on cognitive function in mountaineers prior to and after the climbing. METHODS: After a thorough electronic literature search and selection, eight studies were included in this meta-analysis, and test cycle ranged from 8 to140 days. The eight variables included in this meta-analysis were: trail-making test part B (TMB), finger tapping test--left (FTL), finger tapping test--right (FTR), digit span test forward (DSF), digit span test backward (DSB), wechsler memory scale visual (WMSV), aphasia screening test--visual motor errors(AST-vis), aphasia screening test--verbal items (AST-ver). The effect sizes and Forest Plots of these eight variables were generated. RESULTS: Five variables (trail-making test part B (TMB), ES = 0.39; digit span test forward (DSF), ES = 0.57; finger tapping test--right (FTR), ES =0.50; finger tapping test--left (FTL), ES =0.16; wechsler memory scale visual (WMSV), ES =0.63; ) out of eight were significantly improved after high-altitude mountaineering, while ES values of digit span test backward (DSB), aphasia screening test--verbal items (AST-ver) and aphasia screening test--visual motor errors(AST-vis) did not show significant improvement after the mountaineering. CONCLUSIONS: Our findings have some limitations arising from methodological issues inherent in the meta-analysis and we could not explain the high heterogeneity between studies. Despite such limitations, the current study has the strength of being the first meta-analysis trying to specify cognitive function of mountaineers compared with before and after high-altitude mountaineering. High-altitude mountaineering, as a short-term plateau exercise, has no significant negative impact on the cognitive function of climbers. Future research is needed for a long period of high-altitude mountaineering.

Біомеханічні аспекти раціоналізації процесу навчання рухів у процесі технічної підготовки спортсменів

The article is devoted to the current problem - increasing the efficiency of the trainingprocess and technical training through the use of theoretical and practical developments and opportunities of sports biomechanics, the introduction of biomechanical technologies, expansion of the role of didactic component of the training process as the major means of formation of efficient didactic platform for improving human motor activity during sports engagement.Objective. Analysis of biomechanical aspects of rationalization of the process of learningmovements in the process of technical training of athletes. Methods. Theoretical analysis and generalization of data from special scientific and methodological literature, the Internet and practical experience. Results. The didactic process of sports training aimed at learning new motor actions and improving the already mastered, is constantly changing and requires from the teacher-coach new methodological approaches and creative understanding of its content. The provisions highlighted in the article on the rationalization of the process of learning movements during technical training of athletes are confirmed by their practical implementation in the training process of athletes of different qualifications. The author concludes that the theoretical basis of technical training of athletes in various sports events is formed by the basic provisions of sports biomechanics, one of the directions of which is the pedagogical component of rationalizing the process of technical training, which allows to increase sports practice efficiency through motor action analysis and its constructive synthesis, sunstantiation sports technique, its construction, finding ways to improve, find and understand the causes of motor errors and effective ways to avoid them, including ways and means of their occurrence prevention.

The Use of Dynamic Weight Support with Principles of Infant Learning in a Child with Cerebral Palsy: A Case Report

Aims Typical infant movement is characterized by a high degree of motor exploration, error, and variability. However, children with cerebral palsy (CP) often cannot create these experiences due to their neuromotor impairments. The purpose of this case study is to describe a 6-month course of physical therapy (PT) incorporating principles of infant motor learning using dynamic weight support (DWS) in a child with CP. Methods The child was a 27-month-old girl with diplegic CP who functioned at Gross Motor Function Classification System Level IV. The child received 68 PT sessions over a six-month period. DWS was used during therapy to encourage motor practice. The therapy area was arranged to encourage active exploration, motor variability, and error experience. Gross motor function, postural control, parent perception of performance, and parent satisfaction were measured before, during, and after the course of therapy. Results Gross motor function increased during the treatment beyond the level predicted from natural progression. Postural control fluctuated and demonstrated no appreciable improvement. Parent-perceived performance and satisfaction improved on three of four goals. Conclusions Using DWS to incorporate principles of infant learning may have facilitated the development of gross motor skills in a child with diplegic CP.

Comparison of an Off-Line Optimized Firing Angle Modulation and Torque Sharing Functions for Switched Reluctance Motor Control

In this paper, a comparison of the simple firing angle modulation method (FAM) and the more advanced torque sharing function (TSF)-based control of switched reluctance motor (SRM) is presented. The off-line procedure to tailor and optimize the parameters of chosen methods for off-the-shelf SRM is explained. Objective functions for optimization are motor efficiency, torque ripple, and integral square error. The off-line optimization uses a finite element method (FEM) model of the SRM. The model was verified by measurement on the SRM. Simulation results showed that FAM has comparable efficiency to TSF, but has a much higher value of torque ripple. The presented off-line procedure can be used for single or multi-objective optimization.

Printing direction dependent microstructures in direct ink writing

Direct ink writing enables deposition of multiphase filaments with designed microstructures. Using acoustophoresis, we establish a narrow distribution of microparticles at the center of a direct-write nozzle. The distribution shifts and widens after deposition depending on the printing direction. We use particle image velocimetry and digital image analysis to identify flows transverse to the printing direction and characterize particle distributions in the printed filament. Sources of direction-dependent effects include square nozzles, co-deposition of support material, a rotationally asymmetric microstructure established in the nozzle, and speed inaccuracies that occur in 3-axis gantries. We propose an analytical model for predicting print direction-dependent flows and particle distributions as a function of anisotropy of the particle distribution in the nozzle, a disturbed zone near the nozzle, fluid reshaping of the print bead, uniform rotation of the print bead, calibration of the ink and support nozzle positions, and 3D printer motor error. Using the model, we propose strategies for controlling direction dependent microstructures in direct ink writing. The analytical model can be easily adapted to similar direct-write applications to diagnose sources of direction dependent microstructures.

The role of the posterior parietal cortex in saccadic error processing.

Ocular saccades rapidly displace the fovea from one point of interest to another, thus minimizing the loss of visual information and ensuring the seamless continuity of visual perception. However, because of intrinsic variability in sensory-motor processing, saccades often miss their intended target, necessitating a secondary corrective saccade. Behavioral evidence suggests that the oculomotor system estimates saccadic error by relying on two sources of information: the retinal feedback obtained post-saccadically and an internal extra-retinal signal obtained from efference copy or proprioception. However, the neurophysiological mechanisms underlying this process remain elusive. We trained two rhesus monkeys to perform visually guided saccades towards a target that was imperceptibly displaced at saccade onset on some trials. We recorded activity from neurons in the lateral intraparietal area (LIP), an area implicated in visual, attentional and saccadic processing. We found that a subpopulation of neurons detect saccadic motor error by firing more strongly after an inaccurate saccade. This signal did not depend on retinal feedback or on the execution of a secondary corrective saccade. Moreover, inactivating LIP led to a large and selective increase in the latency of small (i.e., natural) corrective saccade initiation. Our results indicate a key role for LIP in saccadic error processing.

Shifting Focus: A Clinician's Guide to Understanding Neuroplasticity for Anterior Cruciate Ligament Rehabilitation.

Neuroplasticity after anterior cruciate ligament (ACL) injury has lingering effects throughout rehabilitation and can influence reinjury risk upon returning to sport if not addressed. Various neural compensatory strategies have been identified following ACL injury, which appear to not be rectified with typical therapy. Thus, further consideration is warranted, addressing the neurophysiologic and neurocognitive aspects of injury when developing a rehabilitation program. Integration of external focus of control strategies, neurocognition, motor planning, unanticipated sensory processing, and load management provide an efficient and effective method for improving motor learning and control throughout the rehabilitation process. Rehabilitation exercises that incorporate unique sports-specific challenges can target the visual processing and anticipatory reaction components of motor control to reduce motor errors that increase injury risk when returning to activity. The neurocognitive demands of returning to sport of efficient decision making and motor patterning amid a rapidly changing competitive environment require novel and clinically implemental strategies.

Intra-articular AAV9 α-iduronidase gene therapy in mucopolysaccharidosis type I canine model

The discovery of cortical neurons responsive to both the observation of another individual’s movement and one’s own physical movement has spurred scientists into utilising this interplay for rehabilitation. The idea that humans can quickly transfer motor programmes or refine existing motor strategies through observation has only recently gained interest in the context of gait rehabilitation but may offer significant promise as an adjunctive therapy to routine balance training. This review is the first dedicated to action observation in postural control or gait in healthy individuals and patients. The traditional use of action observation in rehabilitation is that the observer has to carefully watch pre-recorded or physically performed actions and thereafter imitate them. Using this approach, previous studies have shown improved gait after action observation in stroke, Parkinson’s disease and knee or hip replacement patients. In healthy subjects, action observation reduced postural sway from externally induced balance perturbations. Despite this initial evidence, future studies should establish whether patients are instructed to observe the same movement to be trained (i.e., replicate the observed action(s)) or observe a motor error in order to produce postural countermeasures. The best mode of motor transfer from action observation is yet to be fully explored, and may involve observing live motor acts rather than viewing video clips. Given the ease with which action observation training can be applied in the home, it offers a promising, safe and economical approach as an adjunctive therapy to routine balance training.

The Role of Sociodemographic, Clinical and Neuropsychological Variables in Suicide Attempts in Depressed Adolescents.

In this study, we aimed to evaluate the relationship between sociodemographic, clinical and neuropsychological variables and suicide attempts by comparing adolescents with Major Depressive Disorder (MDD) with and without suicide attempt. 30 adolescents with and without suicide attempt were included in this study. Sociodemographic and Clinical Data Form, Schedule for Affective Disorders and Schizophrenia for School-Age Children--Present and Lifetime Version (K-SADS-PL), The Children Depression Inventory (CDI), Beck Hopelessness Scale (BHS), Barratt Impulsivity Scale (BIS) and neuropsychological tests (Go/NoGo test, Stroop test Wisconsin Card Sorting Test) was applied to participants. Depressed adolescents with suicide attempt compared to adolescents without suicide attempt; motor and total impulsivity scores in BIS-11, commission errors in Go/NoGo test which measure motor inhibition, completion time and errors in Stroop 5 which measure interference inhibition and scores of perseveration in Winsconsin Card Sorting Test (WCST) which measure cognitive inhibition were found to be higher. Family history of suicide attempt (OR: 5.87), commission errors (OR: 1.37), perseverative errors (OR: 1.09) ve total impulsivity (OR: 1.05) were remained in the logistic regression model. Results of this study suggested that family history of suicide attempt was the most important factor predicting suicide attempt in adolescents with depression. Other factors predicting suicide attempt were executive dysfunction and impulsivity.

Efficacy of Verbally Describing One’s Own Body Movement in Motor Skill Acquisition

The present study examined whether (a) verbally describing one’s own body movement can be potentially effective for acquiring motor skills, and (b) if the effects are related to motor imagery. The participants in this study were 36 healthy young adults (21.2 ± 0.7 years), randomly assigned into two groups (describing and control). They performed a ball rotation activity, with the describing group being asked by the examiner to verbally describe their own ball rotation, while the control group was asked to read a magazine aloud. The participants’ ball rotation performances were measured before the intervention, then again immediately after, five minutes after, and one day after. In addition, participants’ motor imagery ability (mental chronometry) of their upper extremities was measured. The results showed that the number of successful ball rotations (motor smoothness) and the number of ball drops (motor error) significantly improved in the describing group. Moreover, improvement in motor skills had a significant correlation with motor imagery ability. This suggests that verbally describing an intervention is an effective tool for learning motor skills, and that motor imagery is a potential mechanism for such verbal descriptions.

Observation of Both Skilled and Erroneous Object Lifting Can Improve Predictive Force Scaling in the Observer.

Recent studies have highlighted that the observation of hand-object interactions can influence perceptual weight judgments made by an observer. Moreover, observing salient motor errors during object lifting allows individuals to update their internal sensorimotor representation about object weight. Embodying observed visuomotor cues for the planning of a motor command further enables individuals to accurately scale their fingertip forces when subsequently lifting the same object. However, it is still unknown whether the observation of a skilled lift is equally able to mediate predictive motor control in the observer. Here, we tested this hypothesis by asking participants to grasp and lift a manipulandum after observing an actor’s lift. The object weight changed unpredictably (light or heavy) every fourth to sixth trial performed by the actor. Participants were informed that they would always lift the same weight as the actor and that, based on the experimental condition, they would have to observe skilled or erroneously performed lifts. Our results revealed that the observation of both skilled and erroneously performed lifts allows participants to update their internal sensorimotor object representation, in turn enabling them to predict force scaling accurately. These findings suggest that the observation of salient motor errors, as well as subtle features of skilled motor performance, are embodied in the observer’s motor repertoire and can drive changes in predictive motor control.

Sub-optimality in motor planning is not improved by explicit observation of motor uncertainty

To make optimal decisions under risk, one must correctly weight potential rewards and penalties by the probabilities of receiving them. In motor decision tasks, the uncertainty in outcome is a consequence of motor uncertainty. When participants perform suboptimally as they often do in such tasks, it could be because they have insufficient information about their motor uncertainty: with more information, their performance could converge to optimal as they learn their own motor uncertainty. Alternatively, their suboptimal performance may reflect an inability to make use of the information they have or even to perform the correct computations. To discriminate between these two possibilities, we performed an experiment spanning two days. On the first day, all participants performed a reaching task with trial-by-trial feedback of motor error. At the end of the day, their aim points were still typically suboptimal. On the second day participants were divided into two groups one of which repeated the task of the first day and the other of which repeated the task but were intermittently given additional information summarizing their motor errors. Participants receiving additional information did not perform significantly better than those who did not.