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Honarvar S, Caminita M, Ehsani H, Kwon HJ, Diaz-Mercado Y, Hahn JO, Kiemel T, Shim JK. Interpersonal motor synergy: coworking strategy depends on task constraints. J Neurophysiol 2021; 126:1698-1709. [PMID: 34644124 DOI: 10.1152/jn.00023.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated the role of task constraints on interpersonal interactions. Twenty-one pairs of coworkers performed a finger force production task on force sensors placed at two ends of a seesaw-like apparatus and matched a combined target force of 20 N for 23 s over 10 trials. There were two experimental conditions: 1) FIXED: the seesaw apparatus was mechanically held in place so that the only task constraint was to match the 20 N resultant force, and 2) MOVING: the lever in the apparatus was allowed to rotate freely around its fulcrum, acting like a seesaw, so an additional task constraint to (implicitly) balance the resultant moment was added. We hypothesized that the additional task constraint of moment stabilization imposed on the MOVING condition would deteriorate task performance compared with the FIXED condition; however, this was rejected, as the performance of the force matching task was similar between two conditions. We also hypothesized that the central nervous systems (CNSs) would employ distinct coworking strategies or interpersonal motor synergy (IPMS) between conditions to satisfy different task constraints, which was supported by our results. Negative covariance between coworker's forces in the FIXED condition suggested a force stabilization strategy, whereas positive covariance in the MOVING condition suggested a moment stabilization strategy, implying that independent CNSs adopt distinct IPMSs depending on task constraints. We speculate that in the absence of a central neural controller, shared visual and mechanical connections between coworkers may suffice to trigger modulations in the cerebellum of each CNS to satisfy competing task constraints.NEW & NOTEWORTHY To the best of our knowledge, this is the first study to investigate the coworking behavior or IPMS when an additional task constraint is imposed. Our proposed analytical framework quantifies IPMS and allows for investigating variability in offline (i.e., across multiple repetitions) and online (i.e., across time) control, which is novel in coworking research. Understanding variability while performing a task is essential, as repeating a task is not always possible, as in therapeutic contexts.
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Affiliation(s)
- Sara Honarvar
- Department of Kinesiology, University of Maryland, College Park, Maryland.,Department of Mechanical Engineering, University of Maryland, College Park, Maryland
| | - Mia Caminita
- Department of Kinesiology, University of Maryland, College Park, Maryland
| | - Hossein Ehsani
- Department of Kinesiology, University of Maryland, College Park, Maryland
| | - Hyun Jun Kwon
- Department of Kinesiology, University of Maryland, College Park, Maryland
| | - Yancy Diaz-Mercado
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland
| | - Jin-Oh Hahn
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland
| | - Tim Kiemel
- Department of Kinesiology, University of Maryland, College Park, Maryland.,Program in Neuroscience & Cognitive Science, University of Maryland, College Park, Maryland
| | - Jae Kun Shim
- Department of Kinesiology, University of Maryland, College Park, Maryland.,Department of Mechanical Engineering, University of Maryland, College Park, Maryland.,Program in Neuroscience & Cognitive Science, University of Maryland, College Park, Maryland.,Department of Mechanical Engineering, Kyung Hee University, Yongin-si, South Korea
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Intra-auditory integration between pitch and loudness in humans: Evidence of super-optimal integration at moderate uncertainty in auditory signals. Sci Rep 2018; 8:13708. [PMID: 30209342 PMCID: PMC6135783 DOI: 10.1038/s41598-018-31792-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 08/21/2018] [Indexed: 11/08/2022] Open
Abstract
When a person plays a musical instrument, sound is produced and the integrated frequency and intensity produced are perceived aurally. The central nervous system (CNS) receives defective afferent signals from auditory systems and delivers imperfect efferent signals to the motor system due to the noise in both systems. However, it is still little known about auditory-motor interactions for successful performance. Here, we investigated auditory-motor interactions as multi-sensory input and multi-motor output system. Subjects performed a constant force production task using four fingers in three different auditory feedback conditions, where either the frequency (F), intensity (I), or both frequency and intensity (FI) of an auditory tone changed with sum of finger forces. Four levels of uncertainty (high, moderate-high, moderate-low, and low) were conditioned by manipulating the feedback gain of the produced force. We observed performance enhancement under the FI condition compared to either F or I alone at moderate-high uncertainty. Interestingly, the performance enhancement was greater than the prediction of the Bayesian model, suggesting super-optimality. We also observed deteriorated synergistic multi-finger interactions as the level of uncertainty increased, suggesting that the CNS responded to increased uncertainty by changing control strategy of multi-finger actions.
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Effect of Kinetic Degrees of Freedom on Multi-Finger Synergies and Task Performance during Force Production and Release Tasks. Sci Rep 2018; 8:12758. [PMID: 30143688 PMCID: PMC6109105 DOI: 10.1038/s41598-018-31136-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Accepted: 08/13/2018] [Indexed: 11/08/2022] Open
Abstract
Complex structures present in a human body has relatively large degrees-of-freedom (DOFs) as compared to the requirement of a particular task. This phenomenon called motor redundancy initially deemed as a computational problem rather can be understood as having the flexibility to perform the certain task successfully. Hence, the purpose of our study was to examine the positive impact of extra DOFs (redundant DOFs) during force production tasks. For this purpose, an experimental setup was designed to simulate archery-like shooting, and purposeful organization of a redundant set of finger forces determined the stability of important performance variables as well as accurate and precise performance. DOFs were adjusted by changing the number of fingers explicitly involved in the task. The concept of motor synergy and computational framework of uncontrolled manifold (UCM) approach was used to quantify stability indices during finger force production. As a result, accuracy and precision of the task improved with an increase in DOFs. Also, the stability indices of net finger forces and moment increased with active DOFs of fingers. We concluded that the controller actively utilizes extra DOFs to increase the stability of the performance, which is associated with the improved accuracy and precision of the task.
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Kim Y, Koh K, Yoon B, Kim WS, Shin JH, Park HS, Shim JK. Examining impairment of adaptive compensation for stabilizing motor repetitions in stroke survivors. Exp Brain Res 2017; 235:3543-3552. [PMID: 28879510 DOI: 10.1007/s00221-017-5074-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 08/22/2017] [Indexed: 01/27/2023]
Abstract
The hand, one of the most versatile but mechanically redundant parts of the human body, suffers more and longer than other body parts after stroke. One of the rehabilitation paradigms, task-oriented rehabilitation, encourages motor repeatability, the ability to produce similar motor performance over repetitions through compensatory strategies while taking advantage of the motor system's redundancy. The previous studies showed that stroke survivors inconsistently performed a given motor task with limited motor solutions. We hypothesized that stroke survivors would exhibit deficits in motor repeatability and adaptive compensation compared to healthy controls in during repetitive force-pulse (RFP) production tasks using multiple fingers. Seventeen hemiparetic stroke survivors and seven healthy controls were asked to repeatedly press force sensors as fast as possible using the four fingers of each hand. The hierarchical variability decomposition model was employed to compute motor repeatability and adaptive compensation across finger-force impulses, respectively. Stroke survivors showed decreased repeatability and adaptive compensation of force impulses between individual fingers as compared to the control (p < 0.05). The stroke survivors also showed decreased pulse frequency and greater peak-to-peak time variance than the control (p < 0.05). Force-related variables, such as mean peak force and peak force interval variability, demonstrated no significant difference between groups. Our findings indicate that stroke-induced brain injury negatively affects their ability to exploit their redundant or abundant motor system in an RFP task.
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Affiliation(s)
- Yushin Kim
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Kyung Koh
- Department of Kinesiology, University of Maryland, 0110F School of Public Health, 4200 Valley Drive, College Park, MD, 20742, USA
| | - BumChul Yoon
- Department of Physical Therapy, Korea University, Seoul, Korea
| | - Woo-Sub Kim
- Department of Rehabilitation Medicine, Korea University Guro Hospital, Seoul, Korea
| | - Joon-Ho Shin
- Department of Stroke Rehabilitation, National Rehabilitation Center, Seoul, Korea
| | - Hyung-Soon Park
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Jae Kun Shim
- Department of Kinesiology, University of Maryland, 0110F School of Public Health, 4200 Valley Drive, College Park, MD, 20742, USA.
- Department of Mechanical Engineering, College of Engineering, Kyung Hee University, Yong-In, Korea.
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Koh K, Kwon HJ, Park YS, Kiemel T, Miller RH, Kim YH, Shin JH, Shim JK. Intra-Auditory Integration Improves Motor Performance and Synergy in an Accurate Multi-Finger Pressing Task. Front Hum Neurosci 2016; 10:260. [PMID: 27375457 PMCID: PMC4896966 DOI: 10.3389/fnhum.2016.00260] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/17/2016] [Indexed: 11/20/2022] Open
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.
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Affiliation(s)
- Kyung Koh
- Department of Kinesiology, University of Maryland College Park, MD, USA
| | - Hyun Joon Kwon
- Department of Kinesiology, University of Maryland College Park, MD, USA
| | - Yang Sun Park
- Department of Physical Education, Hanyang University Seoul, South Korea
| | - Tim Kiemel
- 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
| | - Ross H Miller
- Department of Kinesiology, University of Maryland College Park, MD, USA
| | - Yoon Hyuk Kim
- Department of Mechanical Engineering, Kyung Hee University Yongin-Si, South Korea
| | - Joon-Ho Shin
- Department of Stroke Rehabilitation, National Rehabilitation Center Seoul, South Korea
| | - Jae Kun Shim
- 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
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Deficits in motor abilities for multi-finger force control in hemiparetic stroke survivors. Exp Brain Res 2016; 234:2391-402. [PMID: 27071926 DOI: 10.1007/s00221-016-4644-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 04/01/2016] [Indexed: 10/22/2022]
Abstract
The ability to control redundant motor effectors is one of hallmarks in human motor control, and the topic has been studied extensively over several decades since the initial inquiries proposed by Nicholi Bernstein. However, our understanding of the influence of stroke on the control of redundant motor systems is very limited. This study aimed to investigate the effect of stroke-related constraints on multi-finger force control abilities in a visuomotor task. Impaired (IH) and less-impaired hands (LH) of 19 hemiparetic stroke survivors and 19 age-matched control subjects were examined. Each hand repeatedly produced isometric forces to match a target force of 5 N shown on a computer screen using all four fingers. The hierarchical variability decomposition (HVD) model was used to separate force-matching errors (motor performance) into task-relevant measures (accuracy, steadiness, and reproducibility). Task-irrelevant sources of variability in individual finger force profiles within and between trials (flexibility and multiformity) were also quantified. The IH in the stroke survivors showed deficits in motor performance attributed mainly to lower accuracy and reproducibility as compared to control hands (p < 0.05). The LH in stroke survivors showed lower reproducibility and both hands in stroke also had higher multiformity than the control hands (p < 0.05). The findings from our HVD model suggest that accuracy, reproducibility, and multiformity were mainly impaired during force-matching task in the stroke survivors. The specific motor deficits identified through the HVD model with the new conceptual framework may be considered as critical factors for scientific investigation on stroke and evidence-based rehabilitation of this population.
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Koh K, Kwon HJ, Yoon BC, Cho Y, Shin JH, Hahn JO, Miller RH, Kim YH, Shim JK. The role of tactile sensation in online and offline hierarchical control of multi-finger force synergy. Exp Brain Res 2015; 233:2539-48. [PMID: 26019011 DOI: 10.1007/s00221-015-4325-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 05/12/2015] [Indexed: 11/30/2022]
Abstract
The hand, one of the most versatile but mechanically redundant parts of the human body, must overcome imperfect motor commands and inherent noise in both the sensory and motor systems in order to produce desired motor actions. For example, it is nearly impossible to produce a perfectly consistent note during a single violin stroke or to produce the exact same note over multiple strokes, which we denote online and offline control, respectively. To overcome these challenges, the central nervous system synergistically integrates multiple sensory modalities and coordinates multiple motor effectors. Among these sensory modalities, tactile sensation plays an important role in manual motor tasks by providing hand-object contact information. The purpose of this study was to investigate the role of tactile feedback in individual finger actions and multi-finger interactions during constant force production tasks. We developed analytical techniques for the linear decomposition of the overall variance in the motor system in both online and offline control. We removed tactile feedback from the fingers and demonstrated that tactile sensors played a critical role in the online control of synergistic interactions between fingers. In contrast, the same sensors did not contribute to offline control. We also demonstrated that when tactile feedback was removed from the fingers, the combined motor output of individual fingers did not change while individual finger behaviors did. This finding supports the idea of hierarchical control where individual fingers at the lower level work together to stabilize the performance of combined motor output at the higher level.
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Affiliation(s)
- Kyung Koh
- Department of Kinesiology, University of Maryland, College Park, MD, 20742, USA
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Effect of aging on inter-joint synergies during machine-paced assembly tasks. Exp Brain Res 2013; 231:249-56. [PMID: 23995629 DOI: 10.1007/s00221-013-3688-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 08/22/2013] [Indexed: 10/26/2022]
Abstract
In recent years, uncontrolled manifold (UCM) analysis has emerged as an important method to study variability of human movements. The current study investigated the upper extremity movements during typical assembly tasks using the framework of the UCM analysis. Younger and older participants performed machine-paced assembly tasks, while the kinematics of upper extremities were recorded using a motion tracking system. The upper extremity was modeled as a 7 degrees-of-freedom system. The variance of joint angles within the UCM space (V UCM) and the variance perpendicular to the UCM space (V ORT) were analyzed. The results indicated that V UCM were not significantly different for the older and younger groups. For the older group, V ORT was significantly less than the younger group and resulted in less total variance (V TOT) and a better synergy level (Z ΔV ). Therefore, the synergies of upper extremity movement may not be impaired for machine-paced tasks as people age. While current results showed a different effect of aging on the synergies of body movement compared with one previous study, they were in line with a recently proposed theory that for natural tasks, aging people did not have impairment in the ability to organize upper extremity movement into synergies.
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Kim MJ, Karol S, Park J, Auyang A, Kim YH, Kim S, Shim JK. Inter-joint synergies increase with motor task uncertainty in a whole-body pointing task. Neurosci Lett 2012; 512:114-7. [PMID: 22343023 DOI: 10.1016/j.neulet.2012.01.072] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 01/24/2012] [Accepted: 01/30/2012] [Indexed: 11/28/2022]
Abstract
The study investigates the effect of task uncertainty on motor synergies and movement time for a whole-body pointing task employing a Fitts' like paradigm. Thirty-three healthy, young adults were asked to hold a 1.5-m long stick and point it as quickly and accurately as possible to the unmarked center of fixed targets on the ceiling at 150% of the subject's height from the ground. Each subject performed fifteen continuous repetitions for each target size (1cm, 2cm, 3cm, 5cm, 8cm, 13cm and 21cm diameters of circles). It was assumed that the task uncertainty increased as the target size increased. Motion capture was used to collect the data for joint angles in the sagittal plane and uncontrolled manifold (UCM) analysis was used in order to investigate synergistic actions of joints. Results from the study revealed that the movement time decreased as task uncertainty increased. The variability within the uncontrolled manifold (V(UCM)) systematically increased with task uncertainty, resulting in an increase in the index of inter-joint synergies (ΔV), although the pointing task errors (V(ORT)) were consistent across different target sizes. The results suggest that the central nervous system systematically modulates the inter-joint synergies with task uncertainty in the whole-body pointing task without affecting motor performance.
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Affiliation(s)
- Min Joo Kim
- Department of Physical Education, Seoul National University, Seoul, Republic of Korea; Department of Kinesiology, University of Maryland, College Park, MD, USA
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