title: Removal of visual feedback lowers structural variability of inter-digit force coordination during sustained precision pinch.
abstract: This study examined the effects of visual feedback on inter-digit force coordination during a precision pinch. Sixteen healthy, right-handed subjects were instructed to pinch an instrumented apparatus for 1 min with a stable force output. Visual feedback was provided for the first 30s and withdrawn for the second 30s. Detrended fluctuation analysis (DFA) and detrended cross-correlation analysis (DCCA) methods were used to quantify the time-dependent structures of each digit's force and of the force correlation between the digits. After removing visual feedback, the DFA scaling exponent, αDFA, increased from 1.10±0.12 to 1.29±0.13 for the thumb and from 0.95±0.08 to 1.33±0.13 for the index finger (F1,95=372.47, p<0.001); the DCCA scaling exponent, αDCCA, increased from 1.00±0.08 to 1.33±0.13 (t95=20.33, p<0.001). Structural changes were observed beginning with the first 5s epoch after the removal of visual feedback. The results provide evidence that removing visual feedback lowers the structural variability of inter-digit force coordination. This change is reflected in the high-level control strategy, resulting in the two digits being more tightly coupled under somatosensory feedback without visual inputs.
authors.affiliation: Hand Research Laboratory, Departments of Biomedical Engineering, Orthopaedic Surgery, and Physical Medicine and Rehabilitation, Cleveland ClinicCleveland, OH 44195, USA. ke.li.phd@gmail.com
authors.forename: Ke
authors.initials: K
authors.lastname: Li
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Marquardt
authors.forename: Zong-Ming
authors.initials: ZM
authors.lastname: Li
mesh_terms: D000328:Adult; D056228:Feedback, Sensory / Q000502:physiology*; D005260:Female; D005385:Fingers / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D004856:Postural Balance / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*