Experimental Brain Research最新文献

Combined examination of mental workload and biomechanics during dual-task walking in individuals with lower-limb loss is limited to fixed, but not self-modulated walking pace, for which the latter enables dynamic cognitive-motor behavior as typically engaged during community ambulation. By assessing electroencephalography (EEG) (theta, low/high-alpha power) and biomechanics (gait speed, double limb support, stride width), the cerebral cortical activity underlying mental workload and walking mechanics were examined when individuals with and without lower-limb loss executed a cognitive task (assessed via response time and accuracy) under variable demand (seated and walking). Both populations maintained walking mechanics (unchanged gait speed, double limb support, stride width) during dual-task walking across demand and exhibited similarly elevated neurocognitive engagement (e.g., attention, action monitoring) indicated by similar theta power increase and low/high-alpha power decrease when facing greater demand. However, injured individuals exhibited relative performance decrement (degraded response time/accuracy), which suggests attenuated cognitive-motor efficiency relative to uninjured (i.e., similar cortical activity across groups with degraded performance). Moreover, while uninjured individuals during dual-task walking could robustly engage neurocognitive processes to maintain walking mechanics and successfully attend to the concurrent cognitive task, those with lower-limb loss did not exhibit such a robust recruitment (i.e., unchanged frontal/temporal high-alpha power). Such alterations in individuals with lower-limb loss leads to maintenance of walking at the cost of a concurrent task. The present work informs rehabilitation practice and reveals specific cognitive-motor outcomes for individuals with lower-limb loss in an enhanced ecological context.

Pitching is an essential skill in baseball, requiring precise and well-coordinated neural control. However, elucidating its underlying neural mechanisms remains challenging because of the methodological difficulties in assessing neural activity during dynamic movement. Motor imagery (MI) provides a potential approach for investigating neural control in pitching, as MI of basic movements activates neural processes similar to those during actual movement. This study examined how MI of pitching, with and without visual guidance, modulates corticospinal excitability in muscles involved in pitching. Electromyographic activity was recorded from the flexor carpi radialis (FCR), extensor carpi radialis, first dorsal interosseous, and abductor pollicis brevis (APB) muscles. Corticospinal excitability was evaluated by motor-evoked potential (MEP) amplitudes, elicited by transcranial magnetic stimulation to the primary motor cortex. MEPs were measured during kinesthetic MI across five sports skills, using only MI in Experiment 1 and using MI with a model video (vMI) in Experiment 2. Results showed that both types of baseball-MI significantly facilitated corticospinal excitability in APB, and baseball-vMI significantly facilitated corticospinal excitability in FCR, but not in other recorded muscles compared with those at rest. These results likely reflect the relative contribution and functional role of each muscle and fine motor control in actual pitching. The facilitation in APB was specific to baseball-MI/vMI, and this specificity is further supported by the findings that each sport's MI/vMI selectively facilitated corticospinal excitability in the muscle involved in the imagined movements. These findings provide foundational knowledge and a methodology for investigating the modulation of corticospinal excitability during pitching.

Hand dominance influences motor control, yet the nature of asymmetries in reach-to-grasp coordination remains unclear. We used an immersive, haptic-free virtual environment to examine how hand dominance, object size, and distance shape kinematics and muscle activity during reach-to-grasp actions. Twelve right-handed participants performed unilateral movements with both hands toward virtual objects varying in size and distance. Kinematic and electromyographic data were collected from transport- and grasp-related muscles. A 2 (Hand: dominant, non-dominant) × 3 (Distance: near, middle, far) × 3 (Size: small, medium, large) repeated-measures ANOVA evaluated effects on movement parameters. Transport with the non-dominant hand showed higher peak velocities and accelerations and greater variability in 3-D position compared with the dominant hand. These differences were accompanied by increased triceps brachii activation during late transport, likely reflecting compensatory deceleration and stabilization before grasp. In contrast, grasp kinematics and grasp-related electromyographic activity did not differ significantly between hands. Task parameters modulated both transport and grasp, but object distance more strongly influenced transport, whereas object size more consistently affected grasp. Reach-to-grasp coordination in virtual reality revealed functional specialization between the hands, with asymmetries evident in transport but not grasp. These findings support models proposing a proximal-distal division of motor function between limbs. The results also demonstrate the utility of haptic-free VR as a methodological tool for investigating and potentially training limb-specific motor strategies in healthy individuals.

The aim of this study was to examine the organization of ball-catching movements with different biomechanical structures, which are among the profile elements in rhythmic gymnastics, based on common synergies. An additional goal was to identify specific synergies presumably formed during the performing of movements with increased coordinative complexity. Synergy parameters were derived from simultaneously recorded electromyographic (EMG) data from 16 muscles and joint angle kinematics; factor analysis and principal component analysis were applied. It was found that at the kinematic level, participants demonstrated similar motor control strategies for catching the ball. Interjoint coordination was structured into two modules, independent of the motor task's complexity. The specificity of kinematic modules manifested in a shift of the main peak of interjoint interaction synchronization, driven by the subjective perception of the ball contact moment. At the muscular level, up to five muscle modules were identified, two of which were consistently present across different ball-catching movements. Their function is associated with generating active motions of the upper limb segments and stabilizing the shoulder girdle. The component composition of muscle synergies is largely determined by the movements' biomechanical structure and the presence of a common subtask within them.

The study examined the impact of mind wandering (MW) on situation awareness (SA) under varying task difficulties and pinpointed the sensitive SA indicators. 43 participants completed the shearer status monitoring task under simple and complex tasks. It collected operational performance, SAGAT, SART, eye movements, and EEG data, followed by linear mixed models analysis. The results showed that: (1) During the simple task, MW with meta-awareness led to higher performance and SA compared to MW without meta-awareness. In the complex task, SA of MW without meta-awareness surpassed that of MW with meta-awareness. (2) MW without meta-awareness exhibited longer average fixation durations in the simple task. Furthermore, MW with meta-awareness showed inferior β1 and β2 absolute powers in the complex task. (3) β1 and β2 relative power, β2 absolute power, θ/β1, and θ/β2 weakly correlated with SAGAT in MW with meta-awareness, suggesting potential as sensitive SA indicators. SA moderately negatively correlates with fixation intensity. Conversely, δ and θ relative power, β1 and β2 relative power, β2 absolute power, θ/α1, θ/α2, θ/β1, and θ/β2 weakly correlated with SART in MW without meta-awareness, indicating potential as sensitive SA indicators. Moreover, fixation frequency may be linked to brain alertness levels. (4) As task difficulty increased, performance and SA decreased, whereas eye movement data increased. The research reveals the internal relationship between subconscious MW and SA under different task difficulties, and identifies a series of potentially sensitive physiological indicators. It provides a new perspective and empirical basis for further exploring the impact of MW on SA. The research findings can offer certain references for the optimization of operator training content and the design of information requirements for monitoring interfaces.

Mental fatigue (MF) has a significant impact on performance and decision-making in various contexts. It is considered a transient psychophysiological state characterized by impaired cognition and behavior across a range of dynamic contexts. This condition is related to changes in activity and connectivity across certain brain regions. Despite advances in understanding MF, the neural mechanisms remain unclear, necessitating further investigation. This systematic review synthesizes task-based fMRI evidence on MF during prolonged tasks, identifies convergent activation patterns and methodological gaps, and outlines possible future research. Following PRISMA, we searched PubMed, Web of Science, PsycINFO and Embase until November 6th, 2025. Eligible studies involved healthy participants, a mentally fatiguing task ≥ 30 min, and task-based BOLD fMRI acquired either on-task or in pre/post designs. Study characteristics and fMRI findings were extracted; risk of bias was appraised with NIH tools. Nine studies (n = 235) met the inclusion criteria. Across both designs an increase in MF was recurrently linked to higher activation in prefrontal and salience-related regions (DLPFC/VLPFC/DMPFC, ACC, insula) and the thalamus, while tendencies towards deactivation in posterior cortices (parieto-occipital/precuneus) were observed. Some studies also reported cerebellar effects. This review demonstrates the complexity of the neural correlates of MF and underscores the need for comprehensive research to understand its impact on brain functioning.

The thumb plays a crucial role in hand function, yet its proprioceptive abilities remain poorly understood. Here we quantified dynamic thumb localization ability, as well as how this ability adapts to a perturbation, in unimpaired participants. For this, we developed a novel task in which a robot moved the thumb in a circle and participants pressed a button when they felt their thumb aligning with a target point on a screen, receiving visual error feedback in the form of a ball jumping toward the target after they pushed the button. The task also incorporated a propriovisual rotational perturbation to elicit and measure adaptation. To characterize thumb localization ability, we varied thumb speed and rotation diameter, assessed the effect of the propriovisual rotational perturbation, and compared index finger performance. Following task familiarization, average thumb localization error was relatively consistent, with a constant error (CE) of - 5.9°, variable error (VE) of 25.2°, and absolute error (AE) of 29.2°. Errors did not change significantly with speed or circle diameter. Reversing thumb rotation temporarily increased error followed by rapid error adaptation across the next 20 trials, as would be expected if individuals adapted using a body-centered (movement-aligned) frame of reference rather than a world-centered spatial frame. Localization error was comparable for the thumb and the index finger error for the same task and was correlated with a different, robotic assessment of finger proprioception (ρ = 0.61, p = 0.001). These findings indicate that dynamic thumb localization is somewhat inaccurate, although it can leverage visual feedback within a body-centered reference frame to adapt. Further, in unimpaired adults, the dynamic localization abilities of the thumb and index finger are related.

To explore the association between lymphocyte to high-density lipoprotein ratio (LHR) and pain in Parkinson's disease (PD). In this cross-sectional study, 133 inpatients with PD (84 with pain, 49 without pain) were consecutively recruited. Demographic, clinical, and peripheral immune-inflammatory markers were compared between PD patients with and without pain. Risk factors were identified through binary logistic regression. The independent association of the LHR with pain was assessed using multivariable logistic regression, with progressive adjustment for demographic, clinical, and comorbidity factors. Subgroup analyses were conducted to assess the consistency of the association across different clinical subgroups. Compared with patients without pain, those with pain had higher levodopa equivalent daily dose, more severe motor symptoms, greater levels of anxiety, depression, and sleep disturbances, along with elevated LHR. Binary logistic regression identified LHR (odds ratio [OR] = 3.64, 95% confidence interval [CI] 1.56-8.49, P = 0.003) as independent risk factors for pain. In the multivariable model, adjusted for key covariates including age, sex, disease duration, and major comorbidities, LHR remained a significant and independent risk factor (adjusted OR = 4.50, 95% CI 1.77-11.47, P = 0.002). Subgroup analyses confirmed the stability of this association across age, sex, body mass index, hypertension, diabetes, disease duration, and age at onset, with no significant interactions observed (P > 0.05). In this observational study, a higher LHR was positively associated with pain in PD. Future studies should validate these findings and explore LHR-based interventions.