title: Alterations in Neural Control of Constant Isometric Contraction with the Size of Error Feedback.
abstract: Discharge patterns from a population of motor units (MUs) were estimated with multi-channel surface electromyogram and signal processing techniques to investigate parametric differences in low-frequency force fluctuations, MU discharges, and force-discharge relation during static force-tracking with varying sizes of execution error presented via visual feedback. Fourteen healthy adults produced isometric force at 10% of maximal voluntary contraction through index abduction under three visual conditions that scaled execution errors with different amplification factors. Error-augmentation feedback that used a high amplification factor (HAF) to potentiate visualized error size resulted in higher sample entropy, mean frequency, ratio of high-frequency components, and spectral dispersion of force fluctuations than those of error-reducing feedback using a low amplification factor (LAF). In the HAF condition, MUs with relatively high recruitment thresholds in the dorsal interosseous muscle exhibited a larger coefficient of variation for inter-spike intervals and a greater spectral peak of the pooled MU coherence at 13-35 Hz than did those in the LAF condition. Manipulation of the size of error feedback altered the force-discharge relation, which was characterized with non-linear approaches such as mutual information and cross sample entropy. The association of force fluctuations and global discharge trace decreased with increasing error amplification factor. Our findings provide direct neurophysiological evidence that favors motor training using error-augmentation feedback. Amplification of the visualized error size of visual feedback could enrich force gradation strategies during static force-tracking, pertaining to selective increases in the discharge variability of higher-threshold MUs that receive greater common oscillatory inputs in the β-band.
authors.affiliation: Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.|Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Ing-Shiou
authors.initials: IS
authors.lastname: Hwang
authors.affiliation: Physical Education Office, Asian University, Taichung City, Taiwan.
authors.forename: Yen-Ting
authors.initials: YT
authors.lastname: Lin
authors.affiliation: Department of Management Information System, National Chung Cheng University, Chia-Yi, Taiwan.
authors.forename: Wei-Min
authors.initials: WM
authors.lastname: Huang
authors.affiliation: Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Zong-Ru
authors.initials: ZR
authors.lastname: Yang
authors.affiliation: Department of Physical Therapy, College of Medicine, National Cheng Kung University, Tainan City, Taiwan.
authors.forename: Chia-Ling
authors.initials: CL
authors.lastname: Hu
authors.affiliation: School of Physical Therapy, College of Medical Science and Technology, Chung Shan Medical University, Taichung City, Taiwan.|Physical Therapy Room, Chung Shan Medical University Hospital, Taichung City, Taiwan.
authors.forename: Yi-Ching
authors.initials: YC
authors.lastname: Chen
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D004576:Electromyography; D019277:Entropy; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*