Enhanced Performance Stabilization Increases Performance Variability in a Virtual Interception Task.

Risky actions: Why and how to estimate variability in motor performance

We discuss a new framework for understanding the structure of motor control. Our approach integrates existing models of motor control with the reality of hierarchical cortical processing and the parallel segregated loops that characterize cortical-subcortical connections. We also incorporate the recent claim that cortex functions via predictive representation and optimal information utilization. Our framework assumes that each cortical area engaged in motor control generates a predictive model of a different aspect of motor behavior. In maintaining these predictive models, each area interacts with a different part of the cerebellum and BG. These subcortical areas are thus engaged in domain-appropriate system identification and optimization. This refocuses the question of division of function among different cortical areas. What are the different aspects of motor behavior that are predictively modeled? We suggest that one fundamental division is between modeling of task and body whereas another is the model of state and action. Thus, we propose that the posterior parietal cortex, somatosensory cortex, premotor cortex, and motor cortex represent task state, body state, task action, and body action, respectively. In the second part of this review, we demonstrate how this division of labor can better account for many recent findings of movement encoding, especially in the premotor and posterior parietal cortices.

Performance variability during training on simulators is associated with skill transfer

Cue combination in human spatial navigation

Immediate effects of exposure to positive and negative emotional stimuli on visual search characteristics in patients with unilateral neglect

A review of the literature on control of voluntary movements in Down syndrome is combined with original observations on the effects of extensive explanations and practice upon the motor performance in a variety of standardized single-joint motor tasks. After practice, Down syndrome subjects were able to perform fast targeted single-joint movements at speeds comparable with those demonstrated by unimpaired young adults. Down syndrome subjects were able to modulate their preprogrammed reactions in response to external perturbations. However, the patterns of modulation differed significantly from those seen in control subjects. A hypothesis is advanced that the differences between motor performance in DS and in the general population are reflections of adaptive reactions to the impaired decision-making learned during the lifetime in the conditions of a perpetually changing environment.

Our goal in this review is to provide an anatomical framework for the analysis of the motor functions of the medial wall of the hemisphere in humans and laboratory primates. Converging evidence indicates that this region of the frontal lobe contains multiple areas involved in motor control. In the monkey, the medial wall contains four premotor areas that project directly to both the primary motor cortex and the spinal cord. These are the supplementary motor area (SMA) on the superior frontal gyrus and three motor areas buried within the cingulate sulcus. In addition, there is evidence that a fifth motor field, the pre-SMA, lies rostral to the SMA proper. Recent physiological observations provide evidence for functional differences among these motor fields. In the human, no consensus exists on the number of distinct motor fields on the medial wall. In this review, we summarize the results of positron emission tomography (PET) studies that examined functional activation on the medial wall of humans. Our analysis suggests that it is possible to identify at least four separate cortical areas on the medial wall. Each area appears to be relatively more involved in some aspects of motor behavior than others. These cortical areas in the human appear to be analogous to the pre-SMA, the SMA proper, and two of the cingulate motor areas of the monkey. We believe that these correspondences and the anatomical framework we describe will be important for unraveling the motor functions of the medial wall of the hemisphere.

Even in the presence of significant motor limitations, how does physical action continue to be intensely elaborated by the brain? Cerebral palsy (CP) requires motor control to be understood not only as peripheral execution but as an internal construction of action. Between the intention to move and the possible action lies a representational domain in which movement is anticipated, organized, and mentally rehearsed, and it is at this conceptual level that motor imagery becomes central.1 Disregarding this dimension implies restricting rehabilitation to the observable body while neglecting neural processes responsible for intention and motor planning. Thus, shifting the focus to motor imagery means investigating not only whether the child moves, but how actions are planned and simulated before execution. This perspective poses a methodological challenge: how to empirically operationalize internal motor simulation processes. The Hand Laterality Test is widely used as an indirect measure of motor imagery because it requires mental rotation of one's own limb for spatial judgment. However, results based only on mean reaction time or accuracy have been inconsistent. In this context, the study by Breuer Asher et al.2 is particularly relevant for proposing performance variability as a primary indicator of imagery stability. This proposal aligns with contemporary models of motor control and cognition in CP, in which variability is interpreted as a marker of system instability. Accordingly, performance fluctuations should not be regarded as statistical noise but as manifestations of alterations in internal mechanisms of action simulation, supporting the hypothesis of Steenbergen et al.3 that imagery and planning deficits are qualitative and compromise representational consistency. The study by Breuer Asher et al.2 advances the field by showing that motor imagery in children with CP is characterized less by reduced accuracy and more by increased intraindividual variability, particularly in reaction time. By adopting variability as a core variable, the authors provide an integrative explanation for previously discrepant findings, suggesting that the main difficulty lies in performance instability rather than slowness.3, 4 This interpretation is consistent with a recent systematic review demonstrating substantial methodological and outcome heterogeneity, indicating that imagery deficits vary according to task demands, clinical subtype, and functional level.5 Moreover, the proposed composite score integrating accuracy and variability advances the clinical operationalization of motor imagery by offering a quantitative criterion capable of discriminating children with CP from typically developing peers and monitoring this ability over time. Despite these advances, controversies remain regarding the nature of the motor imagery deficit in CP. It is unclear whether increased variability reflects alterations in specific motor simulation mechanisms or broader limitations related to attention, executive functions, or working memory. Steenbergen et al.3 suggested that imagery impairments may be linked to general difficulties in action planning and representation rather than exclusively to simulation capacity. The high prevalence of attention-deficit/hyperactivity disorder in the sample studied by Breuer Asher et al.2 reinforces this complexity, as reaction time instability may reflect attentional fluctuations rather than failures of body representation alone. Thus, it remains unresolved whether variability constitutes a specific marker of imagery or a general index of cognitive instability. Clinically, these findings indicate that motor imagery should not be applied uniformly to children with CP, given distinct imagery performance profiles. Prior assessment is therefore necessary to guide eligibility and intervention design, as children with greater variability tend to respond less consistently to imagery-based protocols and may benefit from combined strategies incorporating attentional support and perceptual feedback, consistent with evidence of partial imagery preservation in unilateral CP.4 For future research, it will be important to determine whether performance variability is sensitive to training and whether it represents a stable trait or a modifiable state. The Article Processing Charge for the publication of this research was funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) (ROR identifier: 00x0ma614). Not required.

This study examined the immediate effects of modulated medium-frequency electrical stimulation (MMFES) combined with motor control exercise (MCE) on lumbar multifidus (LM) activation, motor control, and pain alleviation in patients with recurrent low back pain (rLBP). This randomized controlled trial (RCT) enrolled 42 participants with rLBP, who were randomly allocated into three intervention groups: the MMFES group (15-minute MMFES), the MCE group (15-minute sham MMFES + 30-minute MCE), and the combined (COMB) group (15-minute MMFES + 30-minute MCE). Electrodes were placed bilaterally 3 cm lateral to L3/L5 spinous processes. The MCE protocol involved quadruped rocking backward exercises performed in sets of 15 repetitions, with 8–12 sets per session and 1-minute rest intervals between sets. Outcome measures, including LM activation, motor performance, and numerical pain rating scale (NPRS), were assessed at baseline and immediately post-intervention. LM activation was quantified via musculoskeletal ultrasound imaging by measuring muscle thickness at rest and during maximal voluntary isometric contraction (MVIC). These measurements were used to calculate the LM activation ratio using the formula： LMACT Rate（%）=(LMMVICLMREST)/ LMREST×100%. Motor performance was operationalized as knee flexion angle during the quadruped rocking backward, with larger angles indicating superior motor control. Intergroup comparisons were analyzed using independent samples t-tests or Kruskal-Wallis tests, while intragroup differences were evaluated via paired samples t-tests or Wilcoxon signed-rank tests. The COMB group exhibited superior outcomes versus the other groups in all measures (P < 0.05), including higher LM activation ratios (vs. MMFES: d = 0.32; vs. MCE: d = 0.79). Post-intervention, the COMB group demonstrated a 61% increase in LM activation (from 13.87% to 22.25%, P < 0.001), 8.5° improvement in motor performance (from 30.9°±3.1° to 39.4°±2.7°, P < 0.01), and 3.2-point NPRS reduction (from 4.5±1.2 to 1.3±0.9, P < 0.001). The MMFES group showed moderate LM activation gains (P < 0.05) with pain relief and unchanged motor, while the MCE group improved motor performance with unchanged LM activation (P > 0.05) and limited pain relief. The integration of MMFES with MCE demonstrated significant improvements in LM activation, motor performance, and pain symptoms in patients with rLBP. These findings support the application of MMFES as an adjunctive neuromodulatory intervention to address LM activation deficits in rLBP, potentially improving lumbar spine stability and reducing recurrence risk. Further research is warranted to validate the long-term therapeutic efficacy and elucidate the mechanistic basis of MMFES-induced neuromuscular adaptations.

The role of central auditory processing in reading skill development and reading disorders is unclear. The purpose of this study was to examine whether individuals with specific reading disabilities (SRD) have deficits in processing rapidly presented, serially ordered non-speech auditory signals. To this end, we compared 12 children with SRD and 12 children without SRD on their ability to detect differences and similarities in pure tones of 1000 and 2000 Hz when these signals were presented in pairs (same or different tones, randomly ordered) with short (50 ms) versus long (500 ms) inter-stimulus intervals (ISI). Results showed that the children with SRD had significant difficulty in discriminating between pure tones with short, but not long ISI, whereas the controls performed well with both short and long ISI. The two groups did not differ significantly on measures of attention (d2) and performance IQ, and there were no significant correlations between these measures and ISI performance. There were significant correlations between the short ISI performance and phonologic awareness test results when the two groups were combined. These findings support the specific rapid auditory processing deficit hypothesis of SRD. Examination of intra-subject variability in performance indicated that children from the SRD group showed both decrement in performance with time on task and high overall variability in performance as compared to the controls. These findings underpin the importance of using time-series analyses of performance.

\n Neste estudo foi analisado o efeito de distância, velocidade, tamanhos do disco e do alvo, e massas do disco e da manopla, sobre o desempenho motor em movimentos requisitando rapidez e precisão. Para tanto, foram analisadas as características cinemáticas da tarefa de projetar um disco a um alvo com movimento de contato balístico, empunhando uma manopla. Os movimentos foram desempenhados sobre uma base plana e filmados com câmera optoeletrônica de alta freqüência. O estudo foi conduzido em seis experimentos com um grupo único de participantes. Os resultados indicaram que os modelos de controle motor que têm sido empregados para analisar a relação velocidade-precisão em tarefas mais simples não foram apropriados para explicar o comportamento da tarefa utilizada. O controle motor na tarefa demonstrou ser dinâmico e flexível, frente às diferentes restrições de movimento. As seguintes estratégias de controle foram sugeridas na explicação dos resultados: sincronização da maior velocidade e do instante de contato manopla-disco, manutenção na proporção entre as fases aceleração-desaceleração, maior inércia e menor impacto para aumentar a estabilidade de movimento, e o controle da velocidade e da precisão em dimensões independentes. A análise das ações articulares demonstrou as particularidades das estratégias utilizadas pelo sistema no movimento em função das variáveis manipuladas. Em conjunto, esta seqüência de experimentos permitiu uma compreensão mais ampla das estratégias de controle motor empregadas em movimentos com alta demanda de velocidade e de precisão\n

Quantitative analyses of voluntary orofacial motor control in schizophrenia and tardive dyskinesia

We aimed to investigate the acute effects of a continuous cardiovascular exercise on retrieval and savings while learning a discrete motor skill. Forty participants, aged 18-35 years were randomly divided into 2 groups, Exercise Group (EG), which practiced an underarm dart-throwing task and performed cardiovascular exercise before the retention test, and Control Group (CG), which had the same practice conditions of EG without the exercise session. The groups were submitted to 14 blocks of 10 trials on 2 consecutive days. On day 1, there was an acquisition phase; on day 2, the first block was run the retention and the others for savings. We assessed the motor performance through absolute and variable errors. Our results demonstrated that cardiovascular exercise did not impact the accuracy and variability of the motor performance either on the retention test or relearning rate. We concluded that continuous cardiovascular exercise does not influence the retrieval and savings during discrete motor skill learning.

PURPOSE Coaches and sport scientists who use tests to monitor performance of athletes need to consider seasonal changes and random variation in performance when drawing conclusions about observed changes. We report here the seasonal changes and variability in power of competitive cyclists. METHODS 12 male cyclists performed tests of peak power (continuous ramp protocol) and mean power (simulated 4-km time trial) on a Kingcycle with SRM cranks in each of five sessions during three phases (base, pre-comp, comp) of a racing season. Repeated-measures analysis of logtransformed power provided mean changes in performance (%) between phases and within-cyclist variability in performance (as a coefficient of variation, CV) between sessions <2 wk apart and between sessions in different phases. RESULTS Peak power increased from the base phase to the pre-comp phase on average by 4.3%, and by a further 2.5% from the pre-comp to comp phase. Corresponding increases in 4-km mean power were 4.6% and 4.3%. The 95% likely limits for these changes were • ±2.5%. The CV for peak power was 1.3% for sessions separated by <2 wk and 1.2% for sessions in pre-comp and comp phases, but it increased to 3.5% for sessions between the base and other phases. Corresponding CV for mean power were 1.7%, 2.0% and 3.3%. Likely limits for CV were ∼ x0.7 to x1.7. CONCLUSIONS (a) The average cyclist had major gains in peak and mean power between phases of the season. (b) The CV show that there were substantial differences between individuals for changes between base and other phases. (c) We can monitor these changes, because they are larger than the CV for sessions <2 wk apart (which represent the smallest changes that we can monitor confidently in individuals between any sessions). (d) Interventions that might produce small but worthwhile changes in performance over a period of weeks-months need to be researched in pre-comp and comp phases, when the CV are small.

Objective:Risk factors that contribute to brain pathology and cognitive decline among older adults include demographic factors (e.g., age, educational attainment), genetic factors, health factors, and depression (Plassman et al., 2010). Variability within an individual’s performance across cognitive tasks is referred to as dispersion (Hultsch et al., 2002), which appears sensitive to subtle cognitive impairments associated with neurodegenerative pathology in older adults (Bangen et al., 2019; Kälin et al., 2014). Thaler and colleagues (2015) found that dispersion across domains of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was a useful indicator of cognitive changes associated with cardiovascular disease and mortality. Also, research by Manning and colleagues (2021) found that elevated ratings of depression and anxiety in older adults was associated with greater dispersion across neuropsychological testing. The present study aimed to replicate findings that greater dispersion in neuropsychological performance is associated with impaired neurocognitive performance and greater self-reported depression among older adults who present for neuropsychological evaluation with cognitive concerns.Participants and Methods:Neuropsychological testing data was obtained from a university hospital. Chart reviews were conducted on 369 participants who met initial criteria (60 years or older with testing data from the RBANS Form A, Wechsler Test of Adult Reading, and Geriatric Depression Scale [GDS]). Retrospective analyses were conducted on a final sample of 293 participants from 60 to 94 years old (Mage = 74.41, SDage = 7.43; 179 females, 114 males). Diagnoses were used for group comparisons between cognitively intact individuals with subjective cognitive complaints (SCC, n = 49), persons with Mild Neurocognitive Disorder (mND, n =137), and persons with Major Neurocognitive Disorder (MND, n = 107).Results:As expected, results indicated that higher dispersion was related to lower Total RBANS Scores (r = -0.54, p &lt; .001) and significant differences across diagnostic groupings (F(2, 289) = 29.19, p &lt; 0.001; SCC, mND, MND) indicated that variability in performance was an indicator of greater neurocognitive impairment. Contrary to expectations, greater dispersion was very weakly associated with lower reported depressive symptomatology (r = -0.13, p = 0.03). A three-stage hierarchical linear regression was conducted with the RBANS Coefficient of Variation (CoV) as the dependent variable and three predictor variables (Age, Total RBANS, Total GDS). The regression analysis results indicated that age was not a significant predictor, but both Total RBANS and GDS Scores were. The most important predictor was Total RBANS Scores which uniquely explained 21% of the variation in dispersion.Conclusions:This study adds to the current literature regarding the clinical utility of dispersion in neuropsychological performance as an indicator of early and subtle neurocognitive impairment. Depressive symptom reporting was expected to help predict the degree of variability, but this factor was only weakly associated with the RBANS CoV.Limitations of this study include its retrospective use of archival data and the restricted range on some variables of interest. Further research is needed to examine the relative utility of different measures of dispersion and why increased cognitive performance variability is related to neurocognitive impairment and decline.