Journal of Motor Behavior最新文献

Chronic exposure to manganese in occupational settings such as welding is known to accumulate in the basal ganglia and disrupt motor control. Although clinical symptoms emerge only after considerable neural damage, subtle motor deficits may exist in asymptomatic individuals. This study aimed to identify such subclinical motor alterations by examining multi-finger coordination in professional welders. Nine professional welders with more than 20 years of welding experience and ten age-matched healthy controls participated in the study. Participants performed three isometric finger force tasks: a maximal voluntary contraction task to assess maximal finger forces, a single-finger ramp task to evaluate finger enslaving, and a multi-finger quick pulse task to analyze motor synergies and anticipatory synergy adjustments (ASA). Surface electromyogram was recorded to quantify muscle co-contraction. Compared to controls, welders exhibited reduced motor synergy strength, delayed and decreased ASA, and increased antagonist muscle co-contraction. These findings suggest that long-term occupational welding exposure, which involves manganese as a major component, is associated with subtle but measurable alterations in motor coordination and neural control strategies, even in the absence of clinical symptoms. Multi-finger synergy analysis and co-contraction metrics may serve as sensitive markers for detecting early motor dysfunction in populations occupationally exposed to neurotoxic substances.

We investigated the acute effects of moderate alcohol consumption on implicit and explicit motor learning in young adult male social drinkers. Two experiments used the Serial Reaction Time Task to test whether alcohol intake before practice (Experiment 1) or immediately after practice (Experiment 2) affects implicit and explicit motor learning. Participants (n = 160) were randomly assigned to eight subgroups defined by learning type (implicit vs. explicit), condition (alcohol vs. placebo), and experiment, with 20 participants per subgroup. Alcohol groups ingested vodka mixed with orange soda (Fanta^®, 1:4; 0.4 g/kg ethanol), whereas placebo groups received orange soda sprayed with vodka. Explicit groups memorized the repeating sequence before practice and were informed when repeated-sequence blocks began; implicit groups practiced without declarative knowledge. Participants completed seven practice blocks and a one-week retention test. Performance was quantified by a Change Score (response time difference between repeated and pseudorandom sequences), and declarative knowledge by sequence identification/recognition. Alcohol intake did not affect performance improvements or retention whether consumed before or after practice, regardless of learning condition. We conclude that moderate alcohol consumption does not impair motor memory encoding or consolidation under implicit or explicit motor learning mechanisms.

This study aimed to contribute to the existing literature regarding reference values for knee joint-position sense assessments in healthy-young individuals, and to investigate which protocol- and individual-related factors produce higher accuracy. A cross-sectional study was conducted with 62 participants. Joint-position sense was assessed to an extreme (20°) and an intermediate (45°) target angle in three test positions, and expressed in absolute angular errors. In sitting/prone positions, concentric and eccentric repositionings were performed. Standing tests involved unilateral and bilateral squats. Reference values in sitting position were between 2.7°-3.7°, in prone 4.0°-4.9°, and in standing, between 2.4°-3.0° in unipedal and 3.0°-4.3° in bipedal. Significantly higher errors were found in prone position, compared to sitting and standing (p < 0.001). Bipedal tests produced significantly higher errors than unipedal (p = 0.001). At 45°, errors were in general higher in sitting/prone, but lower in standing tests (p < 0.05). Errors were not different between concentric/eccentric repositionings, dominant/non-dominant limbs, and male/female participants (p > 0.05). Reference data was provided covering different knee joint-position sense assessments. Regarding protocol-related factors: prone position produced higher errors; extreme angles produced lower errors in sitting/prone tests, but higher in standing, in which bipedal tests produced more errors than unipedal. Individual factors seem not to influence knee joint-position sense.

Chronic ankle instability (CAI) affects up to 40% of individuals following lateral ankle sprains, leading to persistent sensorimotor deficits and functional limitations. This investigation examined the immediate effects of stochastic resonance (SR) electrical stimulation on postural control during visually perturbed walking in individuals with CAI (NCT06484712). Twenty-one adults with unilateral CAI participated in this study. Participants walked on a self-paced treadmill while exposed to mediolateral visual perturbations, both with and without the SR stimulation applied at the ankle, shank, and hip. Using a motion capture system, we investigated foot placing techniques, subtalar joint kinematics, and center of mass (CoM) excursion during the first eight steps after perturbation onset. SR stimulation significantly reduced mediolateral CoM excursion (p = 0.013, η² = 0.272) and peak movement (p = 0.038, η² = 0.198) on the affected side without changing local joint kinematics or stepping strategies. These results imply that SR rather than peripheral motor processes influence higher-order sensorimotor integration. Especially in addressing ongoing sensorimotor deficits that affect daily mobility and function, the selective enhancement of global stability measures during functional locomotor tasks offers compelling support for SR's therapeutic potential in rehabilitation protocols for individuals with CAI.

Vector coding is widely used to assess coordination and variability in movement control, yet its application is typically limited to bivariate analyses that focus on two segments or joints (e.g., knee-ankle coupling), despite human movement involving multiple interacting joints. Recent methodological advances have introduced an ellipse-based vector coding approach that enables coordination analysis in higher-dimensional spaces. Because gait speed systematically alters lower-limb kinematics, this study examined both bivariate and trivariate coordination variability of the lower extremity across the hip, knee, and ankle joints using an ellipse-based vector coding method, and compared these measures between slow and fast walking speeds. Mean between-cycle variability was computed to assess overall speed-related changes in coordination dynamics during the stance and swing phases. To determine when speed specifically affects coordination, statistical nonparametric mapping was applied across the entire gait cycle. Cross-correlation analyses compared variability patterns between bivariate and multivariate couplings. Results showed increased bivariate and trivariate coordination variability at faster walking speeds, with strong similarity in cross-correlation observed across knee-ankle, hip-ankle, and hip-knee-ankle couplings (from 0.82 to 0.96). These findings indicate the ankle's key role in driving variability and suggest that ankle-involving bivariate couplings capture the essential features of trivariate coordination during walking.

This study aimed to investigate the effects of attentional focus (internal vs. external) and cognitive dual-tasking on gait variability in healthy adults. Walking, as a fundamental human motor pattern, is influenced by cognitive and attentional demands. Twenty healthy participants (10 men and 10 women) participated in this quasi-experimental within-subjects study. Participants completed four walking conditions: normal walking, walking with an internal focus, walking with an external focus, and walking while performing a cognitive dual-task (counting backward from 100). Kinematic data were recorded using a Vicon motion capture system and analyzed using Python. Key outcome measures included spatial-temporal gait parameters, local dynamic stability assessed via the Lyapunov exponent, and motor variability based on the uncontrolled manifold (UCM) framework. Repeated measures ANOVA and post hoc tests revealed that attentional focus and cognitive load significantly influenced walking patterns. Dual-tasking led to slower gait speed, increased step width, and a higher percentage of double support, alongside increased Lyapunov exponents and decreased UCM indices-indicating reduced gait stability and adaptability. Conversely, external focus improved most gait parameters. These findings highlight the critical role of attentional strategies in maintaining gait stability and suggest their relevance in motor control, learning, and rehabilitation programs.

In unchallenging single-leg balance (SLB) tasks, the lower limbs demonstrate symmetrical control and stability. Balance asymmetries between the legs are expected to increase with task demands, being evident in complex motor tasks. In this study, we tested two hypotheses: (1) whether task complexity increases asymmetries in a single-leg balance task, and (2) whether general and specific foot preferences are correlated with performance asymmetries. Twenty-seven right-footed young adults participated by performing two tasks: (1) SLB on a stable surface (SB); and (2) SLB on an unstable surface in the anteroposterior axis (UB). Stability was provided by placing the pressure plate on the floor or on an unstable platform with a hemi-cylinder-shaped support base. Balance performance measurements were obtained through center of pressure displacement and area. Task complexity affected asymmetry direction, showing better performance with the left leg in the UB. The magnitude of asymmetries did not increase between tasks. No correlations were found between preference and performance, with preference matching the side of better performance in only ≅ 50% of the participants. These findings show that more complex motor tasks are necessary for the potential advantages of hemispheric specificity related to motor control balance mechanisms to be manifested.

COVID-19 is primarily a respiratory illness, but it has been linked to persistent neurocognitive deficits. Given the prefrontal cortex's role in cognitive-motor processing and implicit motor learning, this study examined whether individuals recovered from COVID-19 exhibit impairments in reaction time and procedural learning. Eighty-four college students (COVID-recovered n = 24; controls n = 60) completed a remote serial reaction time task. The COVID-recovered group showed significantly slower reaction times than controls (Δ = 47.1; ω² = 0.127). No group differences emerged for implicit learning (Δ = 12.5; ω² ≈ 0). Regression analyses indicated COVID-19 status predicted slower reaction times (β = 0.520, p = 0.048), independent of age, sex, BMI, and physical activity. These findings suggest residual cognitive-motor slowing following COVID-19 without impaired procedural learning.

Accuracy and precision in synchronization and phase coherence have often been used to assess entrainment. However, discrepancies between neural entrainment and behavioral performance have been reported. This study aimed to evaluate motor entrainment to auditory stimuli through phase synchronization measured via finger tapping. Twenty healthy adults participated in a tapping task synchronized with auditory tones presented at six inter-tone intervals (400, 500, 600, 750, 1000, and 2000 ms) over a five-minute period per condition. Phase synchronization strength was quantified from the time-series data of auditory cues and tapping responses. Surrogate data analysis was used to assess the significance of phase synchronization, and effect sizes (Cohen's d) were calculated for each condition. Results showed significant phase coherence at 400, 500, 600, 750, and 1000 ms, with the strongest effect size observed at 400 ms. This condition also had the lowest likelihood of false positives in entrainment detection, suggesting that the 400 ms interval is the most reliable for evaluating motor-auditory entrainment.

The one-target advantage (OTA) refers to faster execution of single-target movements compared to the same movement embedded in a two-target reaching sequence. While well documented in younger adults, little is known about OTA in older adults with age-related motor changes. This study examined whether augmented sensory feedback modulates goal-directed aiming during the OTA paradigm. Thirty right-handed participants (15 younger, 15 older adults) performed one- and two-target aiming tasks under vibrotactile (VT), auditory (A), and no-feedback (NF) conditions. Results showed that reaction time was shorter in the two-target task than in the one-target task under VT feedback (p = .002). Older adults demonstrated significantly shorter movement times with VT than with NF. Older adults showed greater undershooting in the two-target task under NF, which was reduced with VT feedback (p = .011). Additionally, older adults typically spent longer in the time after peak velocity, but VT feedback significantly reduced this duration. Overall, VT feedback improved both temporal and spatial measures, particularly for older adults. Auditory feedback showed limited effects, influencing only TAPV1 (p = .036). Together, these results highlight the potential of VT feedback to mitigate age-related motor performance declines.