Neural Generalization And Activation Trends In Motor Control Cortex During Motor Learning:an Investigation Using Functional Near-infrared Spectroscopy(fNIRS)

Background:Motor learning is a progressive process,necessitating continuous practice and feedback.Distinct characteristics are exhibited at different stages of motor learning.These stages may depend on the activation of diverse neural circuits and cortical areas within the brain.Motor learning involves the coordinated interaction of multiple brain regions,with neural activity in these areas reflecting the long-term storage of motor actions.The mechanisms and processes underpinning these phenomena remain obscure.The primary scientific question addressed in this study is: What are the relationships between motor performance on the learning side(left)and non-learning side(right)and their corresponding cortical activations during the motor learning process? Moreover,how does motor learning influence cortical activity?Objective:1.Investigate the trends in upper limb motor performance,right hemisphere cortical activation,and functional connectivity changes during the learning side(left)task evaluation in the process of action learning,in order to explore the relationship between motor performance and cortical activation changes.2.Examine the neural generalization of upper limb motor performance and left hemisphere cortical activation during the non-learning side(right)task evaluation following action learning.3.Explore the correlation between upper limb motor performance and right hemisphere cortical activation during the learning side(left)task evaluation in the process of action learning.Methods:In this study,31 right-handed participants were recruited and randomly assigned to either the simple task group(D)or the complex task group(Da T),with both groups completing 10 days of left-sided motor learning training.Motor performance was assessed using the MMDT task completion time,while cortical activation levels were measured using functional near-infrared spectroscopy(fNIRS).Task evaluations were divided into learning-side(left upper limb performing actions)assessments,which included evaluating left upper limb motor performance,left hemisphere activation,right hemisphere activation,and left hemisphere functional connectivity during left upper limb task testing;and non-learning-side(right upper limb performing actions)assessments,which involved evaluating right upper limb motor performance and left hemisphere activation during right upper limb task testing.Generalized Estimating Equations(GEE)were employed to establish marginal models for the statistical analysis of factors influencing motor learning.Independent sample t-tests or Wilcoxon signed-rank tests were used to compare intergroup differences in basic characteristics.Spearman’s correlation analysis was conducted to assess the relationship between motor performance and cortical activation.The level of statistical significance was set at p < 0.05.Results:1.In the context of motor learning,the evaluation of the learning side(with the left upper limb executing the action)encompasses: performance of the left upper limb,activation of the right cortical hemisphere,alterations in left cortical hemisphere activation,and differences in intergroup functional connections within the right hemisphere.1.1 The performance of the left upper limbThe performance of the left upper limb consistently improved in both the simple group(D)and complex group(Da T)(p<0.001),with plateaus appearing on day 7(D)and day 9(Da T)respectively.1.2 Right cortical activation changes1.2.1 Activation of the primary motor area(M1R)and dorsal prefrontal cortex(PFCR)of the right hemisphere progressively decreased during the learning process.This trend began on day 5 of motor learning in both groups(M1R: D group,p=0.011;Da T group,p=0.024;PFCR: D group,p=0.004;Da T group,p=0.034),and persisted until day 10(p<0.05).1.2.2 Activation of the parietal cortex(PLR)of the right hemisphere exhibited decreases at specific time points in both groups(D group: T3,T6,T10,p<0.05;Da T group: T3,T6,p<0.05).1.2.3 The supplementary motor area(SMAR)of the right hemisphere exhibited sustained activation throughout the learning process(p>0.05).1.3 Left cortical activation changesThe activation of the dorsal prefrontal cortex(PFCL)of the left hemisphere decreased(D group: p=0.044;Da T group: p=0.009).There were no statistically significant differences in the other brain areas when comparing pre-and post-learning.1.4 Intergroup comparison of functional connectivity differences in the primary motor control areas of the learning side: The differences in functional connectivity within the right hemisphere between the D and Da T groups increased.2.Changes in motor performance and cortical activation in the right upper limb following motor learning in the left upper limb.2.1 After 10 days of learning on the left side,the motor performance of the right upper limb improved(D group: p<0.001;Da T group: p<0.001).2.2 Post-learning,there were no differences in the activation of the left cortical areas(PFCL,M1 L,PLL,SMAL)in the simple group(D);in the complex group(Da T),there were no differences in the activation of the left cortical areas(PFCL,M1 L,SMAL),however a significant difference was observed in PLL(t=-2.98,p=0.010).3.During motor learning,the correlation between the performance of the learning side’s(left)upper limb task and the right cortical hemisphere was significant,particularly in the right primary motor area(M1R)and dorsal prefrontal cortex(M1R:D,R=0.88;Da T,R=0.83;PFCR: D,R=0.95;Da T,R=0.99).Conclusion:1.With an increase in the number of action learning sessions,the performance of the two difficulty groups entered a rapid learning phase on days 1-2,with a rapid improvement in performance.On days 3-7,they entered a consolidation learning phase,where the rate of improvement slowed down.On days 8-10,they entered a stable plateau phase where little change occurred.The activation levels of the primary motor cortex(M1R)and the dorsolateral prefrontal cortex(PFCR)in the right hemisphere showed a continuous decline trend,while the activation level of the right parietal cortex(PLR)and supplementary motor area(SMA)exhibited a sustained activation trend.2.Action learning can promote motor skill transfer to the non-learning upper limb,while cortical neural generalization may affect changes in the activation levels of the primary motor cortex(M1)and the parietal cortex(PL).3.A strong correlation exists between the improved performance of the left upper limb during action learning and the decreasing trend in the activation levels of the right dorsolateral prefrontal cortex(PFCR)and primary motor cortex(M1R).