Respiratory, postural and spatio-kinetic motor stabilization, internal models, top-down timed motor coordination and expanded cerebello-cerebral circuitry: a review

Human dexterity, bipedality, and song/speech vocalization in Homo are reviewed within a motor evolution perspective in regard to 

(i) brain expansion in cerebello-cerebral circuitry, 
(ii) enhanced predictive internal modeling of body kinematics, body kinetics and action organization, 
(iii) motor mastery due to prolonged practice, 
(iv) task-determined top-down, and accurately timed feedforward motor adjustment of multiple-body/artifact elements, and 
(v) reduction in automatic preflex/spinal reflex mechanisms that would otherwise restrict such top-down processes. 

Dual-task interference and developmental neuroimaging research argues that such internal modeling based motor capabilities are concomitant with the evolution of 
(vi) enhanced attentional, executive function and other high-level cognitive processes, and that 
(vii) these provide dexterity, bipedality and vocalization with effector nonspecific neural resources. 

The possibility is also raised that such neural resources could 
(viii) underlie human internal model based nonmotor cognitions. 
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Doctor of Philosophy

dissertationFalls are one of the most disabling features of aging and are increasingly common in persons with balance-impairments such as Parkinson's disease (PD). Falls can cause physical injuries such as fractures and/or head injuries leading to functional incapacity, increased risk of nursing home admission, and higher mortality rate. Acute muscle fatigue has been shown to exacerbate fall-correlated end-points such as postural control in healthy young and elderly individuals. The majority of studies investigating these effects, however, have focused on static stance postural control, or tasks that fail to incorporate more functional movements such as those requiring components of anticipatory and reactive postural control. The purpose of this study was to document the effects of acute lower extremity muscle fatigue on anticipatory and reactive postural control in persons with PD and to compare those results to the impact of fatigue on healthy elderly and young populations. Additionally, this investigation sought to gain insight into the chronology for postural control recovery following acute muscle fatigue. This dissertation has yielded a background on acute muscle fatigue, followed by a systematic review of the evidence on the effects of muscle fatigue on anticipatory and reactive postural control in healthy older individuals. The focus of the paper then shifts to components of an experimentally designed cohort study examining the effects of acute muscle fatigue on a centrally initiated movement task and a peripherally directed lean-induced fall in persons with PD and neurologically healthy adults. Results indicated that both anticipatory and reactive postural control are altered following acute muscle fatiguing exercise in neurologically healthy young and older adults. Amelioration of fatigue effects is extended beyond 30 minutes for most measures. Recovery occurs more readily for reactive postural control than anticipatory postural control. No statistically significant results were found from fatigue effects on postural control in the full cohort of persons with PD. However, a supplementary analysis revealed that postural control is altered in persons with PD who exercised beyond a minimal threshold of energy expenditure. More research is needed with larger sample sizes and improved construct validity for muscle fatigue in this cohort. The results of this study should serve to heighten awareness regarding the potential negative effects of acute muscle fatigue, including the possibility of falls in clinical and community based exercise settings for older adults at risk for falls

Postural automatisms and biomechanics of gait initiation and obstacle negotiation in parkinson’s disease : characterization and effects of different interventions

A doença de Parkinson (DP) é uma doença neurodegenerativa relacionada à perda da independência funcional, com fenômenos motores, como rigidez, desequilíbrio e alterações na marcha. Os automatismos posturais, incluindo os ajustes posturais antecipatórios (APA) e compensatórios (CPA) são essenciais para o equilíbrio em resposta a uma perturbação e seu uso eficiente pode reduzir a ocorrência de quedas em tarefas cotidianas, como iniciação da marcha e negociação de obstáculos. Evidências apontam os benefícios de programas de exercícios na melhora da locomoção e controle postural na DP, entretanto, poucos estudos investigaram os efeitos sobre os automatismos posturais. Assim, a presente dissertação tem o objetivo de caracterizar as estratégias de automatismos posturais e comportamento motor relacionados à iniciação da marcha e negociação de obstáculos de pessoas com DP e comparar os efeitos de três programas de treinamento sobre esses parâmetros. No capítulo I é feita a apresentação geral e contextualização do estudo. No capítulo II é apresentada uma revisão de literatura, com informações compiladas sobre a DP, os automatismos posturais, a locomoção e como diferentes intervenções podem auxiliar na melhora dos parâmetros alterados. As lacunas identificadas na literatura motivaram a escrita de dois estudos originais. Os objetivos dos estudos foram: 1) analisar e comparar os ajustes posturais e os parâmetros biomecânicos durante a iniciação da marcha e negociação de obstáculos de pessoas com DP rígido-acinética e hipercinética; e 2) analisar e comparar os efeitos de três programas baseados em exercício físico (dança, exercícios em água funda e caminhada Nórdica) sobre os ajustes posturais e os parâmetros biomecânicos na iniciação da marcha e negociação de obstáculos em pessoas com DP. No estudo 1, foram avaliadas, de forma transversal, pessoas com DP divididas por subtipos clínicos (rígidos-acinéticos e hipercinéticos). Para o estudo 2, um ensaio clínico, estes sujeitos foram randomizados em três grupos de intervenção de 22 sessões, sendo avaliados antes e depois. Em ambos os estudos as avaliações incluíram variáveis eletromiográficas, cinéticas e cinemáticas. No estudo I, observamos que o grupo rígido-acinético apresentou maior comprometimento neuromotor, refletido por menor ação antecipatória e compensatória de músculos estabilizadores, menor deslocamento do centro de pressão, maior tempo de duplo apoio e menores comprimento e altura de passo durante as tarefas. Além disso, no estudo II as três intervenções mostraram melhoras nos parâmetros avaliados, sendo mais evidentes nos parâmetros espaço-temporais e músculos de tronco para exercícios em água funda e caminhada Nórdica, enquanto que a Dança promoveu melhores resultados na ação dos músculos de quadril. Nossos resultados são importantes para entender as diferenças no controle motor de pacientes com diferentes manifestações clínicas da DP e para auxiliar na prescrição de programas terapêuticos. Ainda, sugerimos que as três intervenções propostas possuem potencial para a manutenção e melhora neuromotora de pessoas com DP.Parkinson's disease (PD) is a neurodegenerative disease related to loss of functional independence, with motor phenomena such as rigidity, imbalance and changes in gait. Postural automatisms, including anticipatory (APA) and compensatory (CPA) postural adjustments are essential for balance in response to a disturbance and their effective use can reduce the occurrence of falls in everyday tasks, such as gait initiation and obstacle negotiation. Evidence points to the benefits of exercise programs in improving locomotion and postural control in PD, however, few studies have investigated the effects on postural automatisms. Thus, the present dissertation aims to characterize the strategies of postural automatisms and motor behavior related to the gait initiation and obstacle negotiation in people with PD and to compare the effects of three training programs on these parameters. Chapter I presents the general presentation and context of the study. Chapter II presents a literature review, with information compiled about PD, postural automatisms, locomotion and how different interventions can help to improve altered parameters. The gaps identified in the literature motivated the writing of two original studies. The aims of the studies were: 1) to analyze and compare postural adjustments to biomechanical parameters during gait initiation and obstacle negotiation in people with akinetic-rigid (AK-R) and hyperkinetic (HYP) PD; and 2) to analyze and compare the effects of three programs based on physical exercise (Brazilian dance, deep water exercises and Nordic walking) on postural adjustments and biomechanical parameters in gait initiation and obstacle negotiation in people with PD. In study 1, people with PD divided by clinical subtypes (AK-R and HYP) were evaluated in a cross-sectional research. . For study 2, a clinical trial, these subjects were randomized into three intervention groups of 22 sessions, being assessed pre and post. In both studies, evaluations included electromyographic, kinetic and kinematic variables. In study I, we observed that the AK-R group showed greater neuromotor impairment, reflected by less anticipatory and compensatory action of stabilizing muscles, less displacement of the center of pressure, longer double support time and shorter step length and height during tasks. Furthermore, in study II, the three interventions showed improvements in the parameters evaluated, being more evident in spatiotemporal parameters and trunk muscles for deep water exercises and Nordic walking, while dance promoted better results in the action of the hip muscles. Our results are important to understand the differences in motor control of patients with different clinical manifestations of PD and to assist in the prescription of therapeutic programs. In addition, we suggest that the three proposed interventions have the potential to maintain and improve neuromotor performance in people with PD

Postural adjustments and biomechanics during gait initiation and obstacle negotiation: a cmparison between akinetic-rigid and hyperkinetic Parkinson’s disease

Individuals with Parkinson’s disease (PD) exhibit different combinations of motor symptoms. The most frequent subtypes are akinetic-rigid (AK-R) and hyperkinetic (HYP). Motor symptoms, such as rigidity and bradykinesia, can directly affect postural adjustments and performance in daily tasks, like gait initiation and obstacles negotiation, increasing the risk of falls and functional dependence. Objective: To compare postural adjustments and biomechanical parameters during the gait initiation and obstacle negotiation of people with AK-R and HYP PD and correlate with functional mobility and risk of falls. Methods: Cross-sectional study. Thirty-three volunteers with PD were divided into two groups according to clinical motor manifestations: AK-R (n = 16) and HYP (n = 17). We assessed the anticipatory (APA), compensatory (CPA) postural adjustments analyzing kinematic, kinetic and, electromyographic parameters during the gait initiation and obstacle negotiation tests. We applied independent T-tests and Pearson correlation tests for comparisons and correlations, respectively (α = 0.05). Results: In the APA phase of the gait initiation test, compared to the functional HYP group, the AK-R group showed shorter time for single support (p = 0.01), longer time for double support (p = 0.01) accompanied by a smaller first step (size, p = 0.05; height, p = 0.04), and reduced muscle activation of obliquus internus (p = 0.02). Similarly, during the first step in the obstacle negotiation test, the AK-R group showed less step height (p = 0.01) and hip excursion (p = 0.02), accompanied by a reduced mediolateral displacement of the center of pressure (p = 0.02) during APA, and activation of the gluteus medius (p = 0.02) and the anterior tibialis (p = 0.04) during CPA in comparison with HYP group. The findings suggest that people with AK-R present impaired postural adjustments during gait initiation and obstacles negotiation compared to hyperkinetic PD. Based on defined motor symptoms, the proposition presented here revealed consistent postural adjustments during complex tasks and, therefore, may offer new insights onto PD motor evaluation and neurorehabilitation

Postural Control in Individuals with Parkinson’s Disease

Parkinson’s disease is the second most common neurodegenerative disorder in the elderly population. It is a complex, progressive, multisystem disease associated with motor and nonmotor impairments. Postural instability is a crucial component of functional mobility, often overlooked by both clinicians and patients with Parkinson’s disease. It is a refractory drug complication for which rehabilitation is the most effective nonpharmacological aid. However, many interventions are based on empirical experience. Improving knowledge on the pathophysiology of postural control disorders is crucial to understand the multifaceted components affected and thus design specific rehabilitation protocols. This chapter intends to offer a comprehensive overview of the current knowledge on this topic starting from the pathophysiology of postural control disorders occurring in various ecological conditions to the most innovative multidisciplinary rehabilitation approaches

Fifteen years of wireless sensors for balance assessment in neurological disorders

Balance impairment is a major mechanism behind falling along with environmental hazards. Under physiological conditions, ageing leads to a progressive decline in balance control per se. Moreover, various neurological disorders further increase the risk of falls by deteriorating specific nervous system functions contributing to balance. Over the last 15 years, significant advancements in technology have provided wearable solutions for balance evaluation and the management of postural instability in patients with neurological disorders. This narrative review aims to address the topic of balance and wireless sensors in several neurological disorders, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, stroke, and other neurodegenerative and acute clinical syndromes. The review discusses the physiological and pathophysiological bases of balance in neurological disorders as well as the traditional and innovative instruments currently available for balance assessment. The technical and clinical perspectives of wearable technologies, as well as current challenges in the field of teleneurology, are also examined

Effect of Stance Symmetry on Perturbation-Induced Protective Stepping in Persons Poststroke and Controls

Problem Statement: Stepping is a common strategy after a perturbation. Stroke survivors display a predilection for stepping with non-paretic leg. Insight into induced stepping between stroke survivors and age-matched control may guide our understanding for reactive postural control training post stroke. Purpose: To investigate the difference in perturbation-induced stepping between chronic stroke survivors and age-matched controls at three phases of the stepping response: preparation, execution, and landing and association with clinical outcome measures. Procedure: Twenty-one community-dwelling chronic stroke survivors (mean age 59y/o ±13yrs) and 17 age- and gender-matched controls (mean age 54.4y/o ±17yrs) completed this study. Clinical measures of gait, balance, range, sensation, and motor control were assessed. A mechanical weight drop of 10% body weight (BW) was used to create the anterior waist pull perturbation during three stance symmetry positions: equal stance (EQ) and two asymmetrical stance (70% BW on dominant leg and 70% BW on nondominant leg). Ten perturbation trials plus two catch trials at 2% BW were given in a standard randomly order at the three stance positions. Kinematic and kinetic data was collected for perturbation steps. Results: The asymmetrical trials resulted in two types of stepping response, steps with the leg bearing 70% BW (loaded steps – LS) and steps with the leg that had 30% BW (unloaded steps – ULS). All subjects initiated steps more often with their unloaded leg (ULS) in the asymmetrical stance trials. In the stroke group the ULS increased paretic leg stepping compared to EQ (p=0.001) and LS (p=0.001). The stroke group had significantly earlier APA onset with both non-paretic leg (p=0.003) and paretic leg (p=0.028), took significantly more steps with paretic (p=0.01) and non-paretic (p=0.07), shorter step length (paretic, p=0.025 and non-paretic p=0.003), and less change in momentum at landing with paretic leg (p=0.01) compared to controls. Conclusion: Reacting to a perturbation is more challenging for chronic stroke survivors than age- and gender-matched control subjects in the preparation, execution, and landing phase of the stepping response regardless of the leg used. Perturbation training should include stepping with both non-paretic and paretic leg

The Effect of Moderate Parkinson's Disease on the Biomechanics of Compensatory Backwards Stepping

Postural instability leading to falls is one of the major unmet needs in the treatment of Parkinson's disease (PD). The progression of postural instability is not well understood, and a better understanding of the biomechanics underlying the progression of postural instability may be instrumental in the development of more sensitive clinical measures of postural instability and fall risk in PD. The biomechanical analysis of the response to a balance perturbation provides an opportunity to better understand postural instability in PD. This study examined the compensatory stepping response to a backwards pull in participants with moderate PD compared to age-range matched healthy controls. The first study investigated the overall response to a balance disturbance in moderate PD, and found that patients with moderate PD utilized more steps to regain balance, had a longer weight shift time, and used a base-width neutral step as a strategy to regain balance, compared to controls. The second study further investigated the compensatory response by focusing on the preparation phase and found that participants with moderate PD used multiple anticipatory postural adjustments (APAs), resulting in longer liftoff times and significantly different movement in the center of pressure prior to liftoff compared to healthy controls. The third study investigated the effects of PD and step strategy (single step, multiple steps, and a base-width neutral step) on balance recovery and found that participants with moderate PD took significantly longer to recover balance, and that the type of strategy used to respond to the disturbance significantly impacted recovery time. Additionally, the use of a base-width neutral step as the first step in the response emerged as a strategy that has not been previously documented and significantly delays balance recovery. These results suggest that moderate PD significantly impairs the compensatory response to a backwards pull. Furthermore, this impairment could be attributed to a delay in the preparation phase of the step response. This delay was associated with the use of multiple anticipatory postural adjustments and/or the use of a base-width neutral step as the first step in the response. Further study should examine the progression of impairment in these compensatory responses across PD severity levels, and the correlation with fall risk

Biomechanical and neurophysiological mechanisms related to postural control and efficiency of movement: A review

Understanding postural control requires considering various mechanisms underlying a person's ability to stand, to walk, and to interact with the environment safely and efficiently. The purpose of this paper is to summarize the functional relation between biomechanical and neurophysiological perspectives related to postural control in both standing and walking based on movement efficiency. Evidence related to the biomechanical and neurophysiological mechanisms is explored as well as the role of proprioceptive input on postural and movement control.info:eu-repo/semantics/publishedVersio