Extraction of Nonlinear Synergies for Proportional and Simultaneous Estimation of Finger Kinematics

Objective: Proportional and simultaneous estimation of finger kinematics from surface EMG based on the assumption that there exists a correlation between muscle activations and finger kinematics in low dimensional space. Methods: We employ Manifold Relevance Determination (MRD), a multi-view learning model with a nonparametric Bayesian approach, to extract the nonlinear muscle and kinematics synergies and the relationship between them by studying muscle activations (input-space) together with the finger kinematics (output-space). Results: This study finds that there exist muscle synergies which are associated with kinematic synergies. The acquired nonlinear synergies and the association between them has further been utilized for the estimation of finger kinematics from muscle activation inputs, and the proposed approach has outperformed other commonly used linear and nonlinear regression approaches with an average correlation coefficient of 0.91±0.03. Conclusion: There exists an association between muscle and kinematic synergies which can be used for the proportional and simultaneous estimation of finger kinematics from the muscle activation inputs. Significance: The findings of this study not only presents a viable approach for accurate and intuitive myoelectric control but also provides a new perspective on the muscle synergies in the motor control community

比例筋電位制御に向けた筋シナジーの抽出、解釈、および応用の研究

Transfer of human intentions into myoelectric hand prostheses is generally achieved by learning a mapping, directly from sEMG signals to the Kinematics using linear or nonlinear regression approaches. Due to the highly random and nonlinear nature of sEMG signals such approaches are not able to exploit the functions of the modern pros- thesis, completely. Inspired from the muscle synergy hypothesis in the motor control community, some studies in the past have shown that better estimation accuracies can be achieved by learning a mapping to kinematics space from the synergistic features extracted from sEMG. However, mainly linear algorithms such as Principle Compo- nent Analysis (PCA), and Non-negative matrix factorization (NNMF) were employed to extract synergistic features, separately, from EMG and kinematics data and have not considered the nonlinearity and the strong correlation that exist between finger kine- matics and muscles. To exploit the relationship between EMG and Finger Kinematics for myoelectric control, we propose the use of the Manifold Relevance Determination (MRD) model (multi-view learning) to find the correspondence between muscular and kinematics by learning a shared low-dimensional representation. In the first part of the study, we present the approach of multi-view learning, interpretation of extracted non- linear muscle synergies from the joint study of sEMG and finger kinematics and their use in estimating the finger kinematics for the upper-limb prosthesis. Applicability of the proposed approach is then demonstrated by comparing the kinematics estimation accuracies against linear synergies and direct mapping. In the second part of the study, we propose a new approach to extract nonlinear muscle synergies from sEMG using multiview learning which addresses the two main drawbacks (1. Inconsistent synergistic patterns upon addition of sEMG signals from more muscles, 2. Weak metric for accessing the quality and quantity of muscle synergies) of established algorithms and discuss the potential of the proposed approach for reducing the number of electrodes with negligible degradation in predicted kinematics.九州工業大学博士学位論文 学位記番号：生工博甲第372号 学位授与年月日：令和2年3月25日1 Introduction|2 Related Work|3 Extraction of nonlinear synergies for proportional and simultaneous estimation of finger kinematics|4 An Approach to Extract Nonlinear Muscle Synergies from sEMG through Multi-Model Learning|5 Conclusion and Future Work九州工業大学令和元年

Implementing physiologically-based approaches to improve Brain-Computer Interfaces usability in post-stroke motor rehabilitation

Stroke is one of the leading causes of long-term motor disability and, as such, directly impacts on daily living activities. Identifying new strategies to recover motor function is a central goal of clinical research. In the last years the approach to the post-stroke function restore has moved from the physical rehabilitation to the evidence-based neurological rehabilitation. Brain-Computer Interface (BCI) technology offers the possibility to detect, monitor and eventually modulate brain activity. The potential of guiding altered brain activity back to a physiological condition through BCI and the assumption that this recovery of brain activity leads to the restoration of behaviour is the key element for the use of BCI systems for therapeutic purposes. To bridge the gap between research-oriented methodology in BCI design and the usability of a system in the clinical realm requires efforts towards BCI signal processing procedures that would optimize the balance between system accuracy and usability. The thesis focused on this issue and aimed to propose new algorithms and signal processing procedures that, by combining physiological and engineering approaches, would provide the basis for designing more usable BCI systems to support post-stroke motor recovery. Results showed that introduce new physiologically-driven approaches to the pre-processing of BCI data, methods to support professional end-users in the BCI control parameter selection according to evidence-based rehabilitation principles and algorithms for the parameter adaptation in time make the BCI technology more affordable, more efficient, and more usable and, therefore, transferable to the clinical realm

Estudio de sinergias musculares durante actividades de pedaleo

Una sinergia muscular es un mecanismo neurofisiológico mediante el cual el sistema nervioso central coordina la acción de varios músculos a partir de órdenes comunes generadas a nivel espinal. El comportamiento de las sinergias musculares en determinadas tareas motoras cíclicas como las realizadas durante la rehabilitación asistida por un robot (por ejemplo con exoesqueletos) puede proporcionar información cuantitativa sobre aspectos como la recuperación funcional, el aprendizaje motor y el funcionamiento neuromuscular en general. Esta información puede ser de gran utilidad en la optimización de una terapia de rehabilitación. En este proyecto se propone analizar el comportamiento de las sinergias musculares durante tareas de pedaleo en distintas condiciones de resistencia y velocidad. El pedaleo es un tipo de tarea motora cuyas características se asemejan a muchos de los movimiento cíclicos utilizados en terapias de rehabilitación asistida por robots, por lo que supone un buen punto de partida para caracterizar de forma efectiva el comportamiento sinérgico ante cambios de velocidad y de resistencia