title: Intra-Auditory Integration Improves Motor Performance and Synergy in an Accurate Multi-Finger Pressing Task.
abstract: Humans detect changes in the air pressure and understand the surroundings through the auditory system. The sound humans perceive is composed of two distinct physical properties, frequency and intensity. However, our knowledge is limited how the brain perceives and combines these two properties simultaneously (i.e., intra-auditory integration), especially in relation to motor behaviors. Here, we investigated the effect of intra-auditory integration between the frequency and intensity components of auditory feedback on motor outputs in a constant finger-force production task. The hierarchical variability decomposition model previously developed was used to decompose motor performance into mathematically independent components each of which quantifies a distinct motor behavior such as consistency, repeatability, systematic error, within-trial synergy, or between-trial synergy. We hypothesized that feedback on two components of sound as a function of motor performance (frequency and intensity) would improve motor performance and multi-finger synergy compared to feedback on just one component (frequency or intensity). Subjects were instructed to match the reference force of 18 N with the sum of all finger forces (virtual finger or VF force) while listening to auditory feedback of their accuracy. Three experimental conditions were used: (i) condition F, where frequency changed; (ii) condition I, where intensity changed; (iii) condition FI, where both frequency and intensity changed. Motor performance was enhanced for the FI conditions as compared to either the F or I condition alone. The enhancement of motor performance was achieved mainly by the improved consistency and repeatability. However, the systematic error remained unchanged across conditions. Within- and between-trial synergies were also improved for the FI condition as compared to either the F or I condition alone. However, variability of individual finger forces for the FI condition was not significantly decreased as compared to I condition alone. This result indicates an improvement in motor performance is consistent with Bayesian estimation, and changes in multi-finger interaction mostly result in the enhanced motor performance. These findings provide evidence that the central nervous system can take advantage of the intra-auditory integration in a statistically optimal (Bayesian) fashion to enhance motor performance by improving multi-finger synergy.
authors.affiliation: Department of Kinesiology, University of Maryland College Park, MD, USA.
authors.forename: Kyung
authors.initials: K
authors.lastname: Koh
authors.affiliation: Department of Kinesiology, University of Maryland College Park, MD, USA.
authors.forename: Hyun Joon
authors.initials: HJ
authors.lastname: Kwon
authors.affiliation: Department of Physical Education, Hanyang University Seoul, South Korea.
authors.forename: Yang Sun
authors.initials: YS
authors.lastname: Park
authors.affiliation: Department of Kinesiology, University of MarylandCollege Park, MD, USA; Neuroscience and Cognitive Science Program, University of MarylandCollege Park, MD, USA; Applied Mathematics and Statistics, and Scientific Computation Program, University of MarylandCollege Park, MD, USA.
authors.forename: Tim
authors.initials: T
authors.lastname: Kiemel
authors.affiliation: Department of Kinesiology, University of Maryland College Park, MD, USA.
authors.forename: Ross H
authors.initials: RH
authors.lastname: Miller
authors.affiliation: Department of Mechanical Engineering, Kyung Hee University Yongin-Si, South Korea.
authors.forename: Yoon Hyuk
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Department of Stroke Rehabilitation, National Rehabilitation Center Seoul, South Korea.
authors.forename: Joon-Ho
authors.initials: JH
authors.lastname: Shin
authors.affiliation: Department of Kinesiology, University of MarylandCollege Park, MD, USA; Neuroscience and Cognitive Science Program, University of MarylandCollege Park, MD, USA; Department of Mechanical Engineering, Kyung Hee UniversityYongin-Si, South Korea; Department of Bioengineering, University of MarylandCollege Park, MD, USA.
authors.forename: Jae Kun
authors.initials: JK
authors.lastname: Shim
keywords: hierarchical variability; intra-auditory integration; motor performance; multi-finger pressing; multi-finger synergy