A CPG synergy model for evaluation of human finger tapping movements

Abstract—This paper proposes the CPG synergy model – a biomimetic rhythm generator model based on central pattern generators (CPGs) and muscle synergy theory to enable evaluation of rhythmic motions with non-stationary characteristics such as human finger tapping movements. The model consists of multiple CPGs to approximate the complex rhythmic movement of humans, and has the potential to allow evaluation of abnormal movements in patients with motor function impairments such as Parkinson’s disease (PD). To verify the validity of the proposed model, comparison experiments were conducted using model parameters (i.e., syn-ergies, weight coefficients and time-shift parameters) extracted from finger tapping movements performed by individuals in a healthy subject group and a PD patient group. The results showed that the number of synergies, the second moment of synergy shapes and the coefficient of variation of maximum weight coefficients show significant differences for each subject group, and indicated that the model could be used to evaluate irregular rhythmic movements as well as regular ones. I

History Dependence of Freely Chosen Index Finger Tapping Rhythmicity

Highlights: Voluntary, rhythmic, stereotyped, automated motor activities are basic to humans Participants did initial submaximal tapping at low and high target tapping rates Subsequently, they tapped at a freely chosen rate The freely chosen rate was relatively low following the initial low tapping rate The freely chosen tapping rate was found to be history dependent Objective: To test the following hypothesis. Initial submaximal tapping at preset relatively low and high target tapping rates causes a subsequent freely chosen tapping rate to be relatively low and high, respectively, as compared with a reference freely chosen tapping rate. Methods: Participants performed three 3-min bouts of submaximal index finger tapping on separate days. In one bout (C, considered reference), the rate was freely chosen, throughout. In another bout (A), initial tapping was performed at a relatively low target rate and followed by freely chosen tapping. In yet another bout (B), initial tapping was performed at a relatively high target rate, followed by freely chosen tapping. Results: At the end of bout A, the rate was 14.6±23.7% lower than the reference value during bout C (p = 0.023). At the end of bout B, the rate was similar to the rate during bout C (p = 0.804). Conclusions: Initial tapping at a preset relatively low target rate caused a subsequent freely chosen rate to be lower than a reference freely chosen rate. The observation was denoted a phenomenon of motor behavioural history dependence. Initial tapping at a preset relatively high target rate did not elicit history dependence

An Investigation of the Effect of Chewing on Rhythmic Motor Tasks

Chewing gum and walking has traditionally been cited as the quintessentially difficult dual task, but little is known regarding chewing effects on motor control. The aims of this dissertation include describing chewing patterns across adulthood, describing chewing’s influence on secondary motor tasks, and investigate entrainment patterns of chewing and gait per established patterns of coupled oscillators. Three experiments were conducted to describe chewing patterns and to examine the effect chewing has on other motor tasks, particularly walking, in young and old adults. The first experiment used a metronome to manipulate chewing rates and measured associated gait parameters. This experiment established that chewing affects gait. As chewing speed increases or decreases, step rate also changes accordingly. Tasks such as walking, finger tapping, and simple reaction time all slow with advancing age. This experiment established chewing as a task resistant to neuromotor slowing with age. The second experiment examined the effect of chewing on a variety of secondary motor tasks. This experiment confirmed that chewing interferes with performance of a discrete secondary task, such as reaction time, whereas chewing entrains with cyclic movements, like finger tapping and gait. The final experiment varied the timing of when chewing was initiated to highlight the inherent organization of task influence. This experiment confirmed that chewing consistently impacts gait, but not vice versa. A top-down hierarchy where chewing drives changes in gait was substantiated. The physiological basis for the observed behavior is discussed in terms of coupled neural oscillators, such as the central pattern generators in the hindbrain and spinal cord. The findings from the series of experiments highlights oral sensory information as a potentially novel method of influencing movement patterns throughout adulthood. The functional implications of chewing are paramount to survival, but the connection between the mouth and the legs has not been well documented. Understanding the mechanisms associated with this inimitable relationship whereby the mouth is driving leg motion during gait could lead to innovative rehabilitative techniques for gait training

다중손가락 과제 수행 시 인간의 감각 및 인지 처리 과정의 정량화

학위논문 (박사) -- 서울대학교 대학원 : 사범대학 체육교육과, 2021. 2. 박재범.The continuously varied states of human body and surrounding environment require instantaneous motor adaptations and the understanding of motor goal to achieve desired actions. These sensory and cognitive processes have been investigated as elements in motor control during last five decades. Specially, the task dependency on sensory and cognitive processes suggest the effects of movement properties in terms of environment situation and motor goal. However, these effects were mostly empirically summarized with the measurements of either neural activity or simple motor accomplishment unilaterally. The current thesis addresses the quantification of sensory and cognitive processes based on simultaneous measurements of brain activity and synergic motor performance during multi-digit actions with different movement properties. Multi-digit action as a representation of synergic movements has developed into a widespread agency to quantify the efficacy of motor control, as the reason applied in this thesis. In this thesis, multi-digit rotation and pressing tasks were performed with different movement directions, frequencies, feedback modalities, or task complexities. (Chapter 3) The changes of movement direction induced a decrease in motor synergy but regardless of which direction. (Chapter 4 and 5) Increased frequency of rhythmic movement reduced synergic motor performance associate with decreased sensory process and less efficient cognitive process. (Chapter 6) More comprehensive feedback modality improved synergic performance with increased sensory process. (Chapter 7) Increased movement complexity had a consistent but stronger effect as increased frequency on synergic performance and efficiency of cognitive process. These observations suggest that several movement properties affect the contributions of sensory and cognitive processes to motor control which can be quantified through either neural activity or synergic motor performance. Accordingly, those movement properties may be applied in the rehabilitation of motor dysfunction by developing new training programs or assistant devices. Additionally, it may be possible to develop a simplified while efficient method to estimate the contribution of sensory or cognitive process to motor control.시시각각으로 변화하는 신체 상태와 주변 환경의 상호작용 속에서 알맞은 움직임을 수행하기 위해서는 그에 따른 즉각적인 운동 적응(motor adaptation) 과정와 과제 목표에 대한 이해가 필요하다. 이를 위해 인간의 감각 및 인지 처리과정은 운동 제어 분야의 중요한 요소로 여겨졌다. 선행연구에 따르면, 운동 과제에 따라 변화하는 감각 및 인지 처리과정은 주변 환경과 과제의 목표에 따라 움직임의 특성에 영향을 미친다고 보고되어왔다. 그러나 이러한 영향은 대부분 단순한 운동과제 수행 결과 또는 측정된 신경 활동에 의해 경험적으로 요약된 결과에 국한되어 있다. 따라서 본 논문은 다양한 움직임 특성을 가진 다중 손가락 과제 수행 시, 뇌 활동 (Brain activity)과 더불어 손가락들 간의 협응적인 움직임의 수행 결과를 동시 측정하여 과제의 특성에 따른 감각 및 인지 처리과정의 변화를 분석했다. 다중 손가락 과제는 운동 제어의 성능 효율성을 정량화하기 위해 사용되는 대표적인 과제다. 본 논문에서는 다양한 조건의 움직임 방향, 움직임의 주기빈도, 감각 피드백 양식 또는 과제 난이도에 따른 다중 손가락 회전 동작 및 힘 생성 과제를 사용했다. 연구 결과로는, (문단 3) 움직임 방향이 변화하기 전에 변화할 방향에 상관없이 협응적인 움직임이 악화되었다. (문단 4와 5) 움직임의 주기빈도가 증가할수록 협응적인 움직임이 악화됐으며, 이와 관련된 감각 및 인지 처리과정의 효율성도 감소되었다. (문단 6) 단일 감각 피드백 제공조건에 비해 종합적인 감각 피드백은 증가된 감각 처리과정과 함께 협응적인 움직임을 향상시켰다. (문단 7) 과제의 난이도가 증가할수록 협응적인 움직임과 인지 처리과정의 효율성은 감소되었으며, 움직임의 주기빈도 조건에 비해 과제의 난이도에 따라 협응적인 움직임과 인지 처리과정에 미치는 영향은 상대적으로 더 크게 나타났다. 이러한 결과는 움직임 특성에 따른 뇌 활동과 협응적인 과제 수해 결과를 통해 운동 제어 과정에서 감각 및 인지 처리과정의 기여정도를 정량화할 수 있다는 점을 시사한다. 따라서 움직임 특성에 따른 감각 및 인지 처리 과정의 기여정도의 변화는 운동 기능 장애를 가진 사람들의 새로운 재활 훈련 프로그램 및 움직임 보조 장치를 개발하기 위한 실험적인 근거로 적용될 수 있다. 또한 감각 또는 인지 과정이 운동 제어에 미치는 영향을 추정하기 위한 효율적인 방법을 개발하는데 도움이 될 것이다.Chapter 1. Introduction 1 1.1 Problem statement 1 1.2 Study objective 2 1.3 Organization of dissertation 3 Chapter 2. Background 6 2.1 Motor system 6 2.1.1 Ascending pathway 6 2.1.2 Descending pathway 8 2.1.3 Brain networks 9 2.2 Motor synergy 11 2.2.1 Synergy in performance 12 2.2.2 Synergy in muscles 13 2.2.3 Synergy in neurons 14 2.3 Motor control 15 2.1.1 Sensory process 16 2.1.2 Cognitive process 19 Chapter 3. Effect of movement direction: Multi-Finger Interaction and Synergies in Finger Flexion and Extension Force Production 23 3.1 Abstract 23 3.2 Introduction 24 3.3 Method 28 3.4 Results 35 3.4.1 Maximal voluntary contraction (MVC) force and finger independency 36 3.4.2 Timing indices 37 3.4.3 Multi-finger synergy indices in mode space 39 3.4.4 Multi-finger synergy indices in force space 43 3.5 Discussion 44 3.5.1 Finger independency during finger flexion and extension 44 3.5.2 Multi-finger synergies in force and mode spaces 46 3.5.3 Anticipatory synergy adjustment 48 Chapter 4. Effect of Frequency: Brain Oxygenation Magnitude and Mechanical Outcomes during Multi-Digit Rhythmic Rotation Task 51 4.1 Abstract 51 4.2 Introduction 51 4.3 Methods 55 4.4 Results 61 4.4.1 PET imaging 61 4.4.2 Finger forces 62 4.4.3 UCM analysis 64 4.4.4 Correlation between neural activation and mechanics 65 4.5 Discussion 66 4.5.1 Regions involved in feedback 67 4.5.2 Regions involved in feedforward 69 4.5.3 Corporation of feedforward and feedback 71 4.6 Conclusions 72 Chapter 5. Effect of frequency: Prefrontal Cortex Oxygenation during Multi-Digit Rhythmic Pressing Actions using fNIRS 74 5.1 Abstract 74 5.2 Introduction 74 5.3 Method 77 5.4 Results 84 5.4.1 Performance 84 5.4.2 Multi-digit coordination indices 84 5.4.3 Functional connectivity (FC) 87 5.5 Discussion 88 5.6 Conclusion 91 Chapter 6. Effect of Sensory Modality: Multi-Sensory Integration during Multi-Digit Rotation Task with Different Frequency 92 6.1 Abstract 92 6.2 Introduction 92 6.3 Method 94 6.4 Results 100 6.4.1 Performance 100 6.4.2 Multi-digit coordination indices 101 6.5 Discussion 101 6.6 Conclusion 103 Chapter 7. Effect of Task Complexity: Prefrontal Cortex Oxygenation during Multi-Digit Pressing Actions with Different Frequency Components 104 7.1 Abstract 104 7.2 Introduction 104 7.3 Method 106 7.4 Results 112 7.4.1 Performance 112 7.4.2 Multi-finger coordination indices 113 7.4.3 Functional connectivity (FC) 114 7.5 Discussion 115 7.5.1 Relation between Frequency and task complexity 115 7.5.2 Cognitive process in motor control 116 7.5.3 Relation between motor coordination and cognitive process 118 7.6 Conclusion 119 Chapter 8. Conclusions and Future Work 120 8.1 Summary of conclusions 120 8.2 Future work 121 Bibliography 122 Abstract in Korean 160Docto

Sensor Approach for Brain Pathophysiology of Freezing of Gait in Parkinson\u27s Disease Patients

Parkinson\u27s Disease (PD) affects over 1% of the population over 60 years of age and is expected to reach 1 million in the USA by the year 2020, growing by 60 thousand each year. It is well understood that PD is characterized by dopaminergic loss, leading to decreased executive function causing motor symptoms such as tremors, bradykinesia, dyskinesia, and freezing of gait (FoG) as well as non-motor symptoms such as loss of smell, depression, and sleep abnormalities. A PD diagnosis is difficult to make since there is no worldwide approved test and difficult to manage since its manifestations are widely heterogeneous among subjects. Thus, understanding the patient subsets and the neural biomarkers that set them apart will lead to improved personalized care. To explore the physiological alternations caused by PD on neurological pathways and their effect on motor control, it is necessary to detect the neural activity and its dissociation with healthy physiological function. To this effect, this study presents a custom ultra-wearable sensor solution, consisting of electroencephalograph, electromyograph, ground reaction force, and symptom measurement sensors for the exploration of neural biomarkers during active gait paradigms. Additionally, this study employed novel de-noising techniques for dealing with the motion artifacts associated with active gait EEG recordings and compared time-frequency features between a group of PD with FoG and a group of age-matched controls and found significant differences between several EEG frequency bands during start and end of normal walking (with a p\u3c0.05)