Reorganization of functional and directed corticomuscular connectivity during precision grip from childhood to adulthood

Effects of dynamic and isometric motor practice on position control, force control and corticomuscular coherence in preadolescent children

In this study, we investigated the effects of motor practice with an emphasis on either position or force control on motor performance, motor accuracy and variability in preadolescent children. Furthermore, we investigated corticomuscular coherence and potential changes following motor practice. We designed a setup allowing discrete wrist flexions of the non-dominant hand and tested motor accuracy and variability when the task was to generate specific movement endpoints (15-75 deg) or force levels (5-25% MVC). All participants were tested in both tasks at baseline and post motor practice without augmented feedback on performance. Following baseline assessment, participants (44 children aged 9-11 years) were randomly assigned to either position (PC) or force control (FC) motor practice or a resting control group (CON). The PC and FC groups performed four blocks of 40 trials motor practice with augmented feedback on performance. Following practice, improvements in movement accuracy were significantly greater in the PC group compared to the FC and CON groups (p < 0.001). None of the groups displayed changes in force task performance indicating no benefits of force control motor practice and low transfer between tasks (p-values:0.08-0.45). Corticomuscular coherence (C4-FCR) was demonstrated during the hold phase in both tasks with no difference between tasks. Corticomuscular coherence did not change from baseline to post practice in any group. Our findings demonstrate that preadolescent children improve position control following dynamic accuracy motor practice. Contrary to previous findings in adults, preadolescent children displayed smaller or no improvements in force control following isometric motor practice, low transfer between tasks and no changes in corticomuscular coherence.

The correlation between upper body grip strength and resting-state EEG network

Current research in the field of neuroscience primarily focuses on the analysis of electroencephalogram (EEG) activities associated with movement within the central nervous system. However, there is a dearth of studies investigating the impact of prolonged individual strength training on the resting state of the brain. Therefore, it is crucial to examine the correlation between upper body grip strength and resting-state EEG networks. In this study, coherence analysis was utilized to construct resting-state EEG networks using the available datasets. A multiple linear regression model was established to examine the correlation between the brain network properties of individuals and their maximum voluntary contraction (MVC) during gripping tasks. The model was used to predict individual MVC. The beta and gamma frequency bands showed significant correlation between RSN connectivity and MVC (p < 0.05), particularly in left hemisphere frontoparietal and fronto-occipital connectivity. RSN properties were consistently correlated with MVC in both bands, with correlation coefficients greater than 0.60 (p < 0.01). Additionally, predicted MVC positively correlated with actual MVC, with a coefficient of 0.70 and root mean square error of 5.67 (p < 0.01). The results show that the resting-state EEG network is closely related to upper body grip strength, which can indirectly reflect an individual's muscle strength through the resting brain network.

Visuomotor skill learning in young adults with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) have impaired general motor skills compared to typically developed (TD) individuals.

AIMS

To gain knowledge on how young adults with DS learn and retain new motor skills.

METHODS AND PROCEDURES

A DS-group (mean age = 23.9 ± 3 years, N = 11), and an age-matched TD-group (mean age 22.8 ± 1.8, N = 14) were recruited. The participants practiced a visuomotor accuracy tracking task (VATT) in seven blocks (10.6 min). Online and offline effects of practice were assessed based on tests of motor performance at baseline immediate and 7-day retention.

OUTCOMES AND RESULTS

The TD-group performed better than the DS-group on all blocks (all P < 0.001). Both groups improved VATT-performance online from baseline to immediate retention, (all P < 0.001) with no difference in online effect between groups. A significant between-group difference was observed in the offline effect (∆TD - ∆DS, P = 0.04), as the DS-group's performance at 7-day retention was equal to their performance at immediate retention (∆DS, P > 0.05), whereas an offline decrease in performance was found in the TD-group (∆TD, P < 0.001).

CONCLUSIONS AND IMPLICATIONS

Visuomotor pinch force accuracy is lower for adults with DS compared to TD. However, adults with DS display significant online improvements in performance with motor practice similar to changes observed for TD. Additionally, adults with DS demonstrate offline consolidation following motor learning leading to significant retention effects.

Corticomuscular Coherence in Children with Unilateral Cerebral Palsy: A Feasibility and Preliminary Protocol Study

Objective This study assessed the feasibility of corticomuscular coherence measurement during a goal-directed task in children with unilateral cerebral palsy while establishing optimal experimental parameters. Methods Participants (Manual Ability Classification System levels I-III) completed a submaximal isometric goal-directed grip task during simultaneous electroencephalography and electromyography (EMG) acquisition. Results All participants (n = 11, 6 females, mean age 11.3 ±2.4 years) completed corticomuscular coherence procedures. Of the 40 trials obtained per extremity, an average of 29 (n = 9) and 27 (n = 10) trials were retained from the more- and less-affected extremities, respectively. Obtaining measurement stability required an average of 28 trials per extremity. Conclusion Findings from this work support the feasibility of corticomuscular coherence measurement in children with unilateral cerebral palsy. Acquiring 28 to 40 corticomuscular coherence trials per extremity is ideal. The experimental parameters established in this work will inform future corticomuscular coherence application in pediatric unilateral cerebral palsy.

Dynamic motor practice improves movement accuracy, force control and leads to increased corticospinal excitability compared to isometric motor practice

The central nervous system has a remarkable ability to plan motor actions, to predict and monitor the sensory consequences during and following motor actions and integrate these into future actions. Numerous studies investigating human motor learning have employed tasks involving either force control during isometric contractions or position control during dynamic tasks. To our knowledge, it remains to be elucidated how motor practice with an emphasis on position control influences force control and vice versa. Furthermore, it remains unexplored whether these distinct types of motor practice are accompanied by differential effects on corticospinal excitability. In this study, we tested motor accuracy and effects of motor practice in a force or position control task allowing wrist flexions of the non-dominant hand in the absence of online visual feedback. For each trial, motor performance was quantified as errors (pixels) between the displayed target and the movement endpoint. In the main experiment, 46 young adults were randomized into three groups: position control motor practice (PC), force control motor practice (FC), and a resting control group (CON). Following assessment of baseline motor performance in the position and force control tasks, intervention groups performed motor practice with, augmented visual feedback on performance. Motor performance in both tasks was assessed following motor practice. In a supplementary experiment, measures of corticospinal excitability were obtained in twenty additional participants by application of transcranial magnetic stimulation to the primary motor cortex hot spot of the flexor carpi radialis muscle before and following either position or force control motor practice. Following motor practice, accuracy in the position task improved significantly more for PC compared to FC and CON. For the force control task, both the PC and FC group improved more compared to CON. The two types of motor practice thus led to distinct effects including positive between-task transfer accompanying dynamic motor practice The results of the supplementary study demonstrated an increase in corticospinal excitability following dynamic motor practice compared to isometric motor practice. In conclusion, dynamic motor practice improves movement accuracy, and force control and leads to increased corticospinal excitability compared to isometric motor practice.

TV-NARX and Coiflets WPT based time-frequency Granger causality with application to corticomuscular coupling in hand-grasping

The study of the synchronous characteristics and functional connections between the functional cortex and muscles of hand-grasping movements is important in basic research, clinical disease diagnosis and rehabilitation evaluation. The electroencephalogram (EEG) and electromyographic signal (EMG) signals of 15 healthy participants were used to analyze the corticomuscular coupling under grasping movements by holding three different objects, namely, card, ball, and cup by using the time-frequency Granger causality method based on time-varying nonlinear autoregressive with exogenous input (TV-NARX) model and Coiflets wavelet packet transform. The results show that there is a bidirectional coupling between cortex and muscles under grasping movement, and it is mainly reflected in the beta and gamma frequency bands, in which there is a statistically significant difference (p < 0.05) among the different grasping actions during the movement execution period in the beta frequency band, and a statistically significant difference (p < 0.1) among the different grasping actions during the movement preparation period in the gamma frequency band. The results show that the proposed method can effectively characterize the EEG-EMG synchronization features and functional connections in different frequency bands during the movement preparation and execution phases in the time-frequency domain, and reveal the neural control mechanism of sensorimotor system to control the hand-grasping function achievement by regulating the intensity of neuronal synchronization oscillations.

Temporally stable beta sensorimotor oscillations and cortico-muscular coupling underlie force steadiness

As humans, we seamlessly hold objects in our hands, and may even lose consciousness of these objects. This phenomenon raises the unsettled question of the involvement of the cerebral cortex, the core area for voluntary motor control, in dynamically maintaining steady muscle force. To address this issue, we measured magnetoencephalographic brain activity from healthy adults who maintained a steady pinch grip. Using a novel analysis approach, we uncovered fine-grained temporal modulations in the beta sensorimotor brain rhythm and its coupling with muscle activity, with respect to several aspects of muscle force (rate of increase/decrease or plateauing high/low). These modulations preceded changes in force features by ∼40 ms and possessed behavioral relevance, as less salient or absent modulation predicted a more stable force output. These findings have consequences for the existing theories regarding the functional role of cortico-muscular coupling, and suggest that steady muscle contractions are characterized by a stable rather than fluttering involvement of the sensorimotor cortex.