Understanding motor control in humans to improve rehabilitation robots

Recent reviews highlighted the limited results of robotic rehabilitation and the low quality of evidences in this field. Despite the worldwide presence of several robotic infrastructures, there is still a lack of knowledge about the capabilities of robotic training effect on the neural control of movement. To fill this gap, a step back to motor neuroscience is needed: the understanding how the brain works in the generation of movements, how it adapts to changes and how it acquires new motor skills is fundamental. This is the rationale behind my PhD project and the contents of this thesis: all the studies included in fact examined changes in motor control due to different destabilizing conditions, ranging from external perturbations, to self-generated disturbances, to pathological conditions. Data on healthy and impaired adults have been collected and quantitative and objective information about kinematics, dynamics, performance and learning were obtained for the investigation of motor control and skill learning. Results on subjects with cervical dystonia show how important assessment is: possibly adequate treatments are missing because the physiological and pathological mechanisms underlying sensorimotor control are not routinely addressed in clinical practice. These results showed how sensory function is crucial for motor control. The relevance of proprioception in motor control and learning is evident also in a second study. This study, performed on healthy subjects, showed that stiffness control is associated with worse robustness to external perturbations and worse learning, which can be attributed to the lower sensitiveness while moving or co-activating. On the other hand, we found that the combination of higher reliance on proprioception with \u201cdisturbance training\u201d is able to lead to a better learning and better robustness. This is in line with recent findings showing that variability may facilitate learning and thus can be exploited for sensorimotor recovery. Based on these results, in a third study, we asked participants to use the more robust and efficient strategy in order to investigate the control policies used to reject disturbances. We found that control is non-linear and we associated this non-linearity with intermittent control. As the name says, intermittent control is characterized by open loop intervals, in which movements are not actively controlled. We exploited the intermittent control paradigm for other two modeling studies. In these studies we have shown how robust is this model, evaluating it in two complex situations, the coordination of two joints for postural balance and the coordination of two different balancing tasks. It is an intriguing issue, to be addressed in future studies, to consider how learning affects intermittency and how this can be exploited to enhance learning or recovery. The approach, that can exploit the results of this thesis, is the computational neurorehabilitation, which mathematically models the mechanisms underlying the rehabilitation process, with the aim of optimizing the individual treatment of patients. Integrating models of sensorimotor control during robotic neurorehabilitation, might lead to robots that are fully adaptable to the level of impairment of the patient and able to change their behavior accordingly to the patient\u2019s intention. This is one of the goals for the development of rehabilitation robotics and in particular of Wristbot, our robot for wrist rehabilitation: combining proper assessment and training protocols, based on motor control paradigms, will maximize robotic rehabilitation effects

Acute effects of suspension training and other perturbative sources on lower limb strength tasks

Actualment, els dispositius de suspensió són un dels materials més utilitzats per produir pertorbació i enfortir de forma global la majoria de grups musculars. Encara que, manquen evidències dels seus efectes sobre l’extremitat inferior. Així, l’objectiu principal d’aquesta tesi doctoral va ser quantificar la producció de força, l’activitat muscular i la magnitud de la pertorbació a l’esquat búlgar i altres exercicis de l’extremitat inferior en condicions d’inestabilitat. Es van analitzar 18 estudis per dur a terme una revisió sistemàtica (estudi 1) i 75 participants físicament actius van ser reclutats per realitzar els diferents estudis transversals sobre els efectes dels dispositius de suspensió, les superfícies inestables i les vibracions mecàniques (plataforma vibratòria i vibració superposada) en exercicis de l’extremitat inferior (estudis 2-6). Es va confirmar que l’activació a la part inferior del cos només va ser investigada en el concentrat d’isquiosurals en suspensió (estudi 1). La posició i el ritme d’execució (70 bpm) van ser determinants per la producció de força exercida sobre el tirant de suspensió a l’esquat búlgar (estudi 2). El dispositiu de suspensió a l’esquat búlgar va augmentar les forces verticals contra el terra (estudi 3). Sobre el dispositiu la producció de força va ser major quan el nivell d’inestabilitat era baix (estudi 3 i 4), però a nivell muscular el dispositiu va ser igual de demandant que l’exercici tradicional (estudi 3). Un augment de la pertorbació, va incrementar l’activació muscular (estudis 3, 4, 5) i la magnitud de la inestabilitat per l’esquat búlgar i el mig squat amb barra (estudis 4 i 5). Així, la vibració superposada en un dispositiu de suspensió esdevé un repte per incrementar el nivell de pertorbació i millorar la força, la resistència muscular i l’estabilització (estudi 6). A més, els sensors de força són una eina adequada i usable per valorar les forces exercides sobre els dispositius de suspensió, i l’ús de l’acceleròmetre permet determinar la magnitud de la pertorbació que ofereixen els diferents materials desestabilitzadors mesurant l’acceleració del centre de masses corporal.Actualmente, los dispositivos de suspensión son uno de los materiales más utilizados para producir perturbación y fortalecer globalmente la mayoría de los músculos. Aunque, faltan evidencias de sus efectos sobre la extremidad inferior. Así, el objetivo principal de esta tesis doctoral fue cuantificar la producción de fuerza, la actividad muscular y la magnitud de la perturbación en la sentadilla búlgara y otros ejercicios de la extremidad inferior en condiciones de inestabilidad. Se analizaron 18 estudios para llevar a cabo una revisión sistemática (estudio 1) y 75 participantes físicamente activos fueron reclutados para realizar los diferentes estudios transversales sobre los efectos de los dispositivos de suspensión, las superficies inestables y las vibraciones mecánicas (plataforma vibratoria y vibración superpuesta) en ejercicios de la extremidad inferior (estudios 2-6). Se confirmó que la activación en la parte inferior del cuerpo sólo fue investigada en el concentrado de isquiosurales en suspensión (estudio 1). La posición y el ritmo de ejecución (70 bpm) fueron determinantes para la producción de fuerza ejercida sobre el tirante de suspensión en la sentadilla búlgara (estudio 2). El dispositivo de suspensión en la sentadilla búlgara aumentó las fuerzas verticales contra el suelo (estudio 3). Sobre el dispositivo la producción de fuerza fue mayor cuando el nivel de inestabilidad era bajo (estudio 3 y 4), pero a nivel muscular el dispositivo fue igual de demandante que el ejercicio tradicional (estudio 3). Un aumento de la perturbación incrementó la activación muscular (estudios 3, 4, 5) y la magnitud de la inestabilidad en la sentadilla búlgara y la media sentadilla con barra (estudios 4 y 5). Así, la vibración superpuesta en un dispositivo de suspensión se convierte en un reto para incrementar el nivel de perturbación y mejorar la fuerza, la resistencia muscular y la estabilización (estudio 6). Además, los sensores de fuerza son una herramienta adecuada y usable para valorar las fuerzas ejercidas sobre los dispositivos de suspensión, y el uso del acelerómetro permite determinar la magnitud de la perturbación que ofrecen los diferentes materiales desestabilizadores midiendo la aceleración del centro de masas corporal.Nowadays, suspension devices are one of the most widely used pieces of equipment to produce perturbation and strengthen most muscle groups globally. However, there is a lack of evidence of their effects on the lower limb. Thus, the main objective of this doctoral thesis was to quantify force production, muscle activity and the magnitude of perturbation in the Bulgarian squat and other lower extremity exercises under unstable conditions. Eighteen studies were analysed for a systematic review (study 1) and 75 physically active participants were recruited to perform the different cross-sectional studies on the effects of suspension devices, unstable surfaces, and mechanical vibrations (vibration platform and superimposed vibration) on lower limb exercises (studies 2-6). It was confirmed that lower body activation had only been previously investigated in the suspended hamstring curl (study 1). Position and pace (70 bpm) were determinants for the force exerted on the suspension strap in the Bulgarian squat (study 2). The suspension device in the Bulgarian squat increased the vertical ground reaction forces (study 3). The force production was higher on the device when the level of instability was low (study 3 and 4), but for muscle activity the device was just as demanding as a traditional exercise (study 3). Increased perturbation enhanced muscle activation (studies 3, 4, 5) and the magnitude of instability in the Bulgarian squat and barbell half-squat (studies 4 and 5). Thus, superimposed vibration on a suspension device becomes a challenge to increase the level of perturbation and improve strength, muscular endurance, and stabilisation (study 6). In addition, load cells are a suitable and practical tool to assess the forces exerted on suspension devices, and the use of an accelerometer makes it possible to determine the magnitude of the perturbation offered by different equipment providing instability by measuring the acceleration of the body's centre of mass

Technology from the Perspective of Society and Public Interest

The ultimate goals of this study were to determine ways to reconcile technology with public interest and to understand the relationship between what we know and how we feel about technology. To achieve the goals, related literatures were reviewed; the mechanism of technology development was described with empirical data; and human perception of technology was tested with a survey. The duality of technology that implied technological inherencies of technical reason and social meanings was the principle assumption of the study. Neutrality of technology becomes a myth with the presence of social meanings embodied in technology. Given the huge impact of technology on human societies, the absence of neutrality is, in turn, attributed to the necessity for policy. Analyses of eight empirical cases of technology in history based on the method of grounded theory provided core categories of technical progress, economic values, and social inclinations. Upon the core categories and concepts corroborated by the cases, the mechanism of technology development appeared to be a concatenation of the interactions between technical progress and social demand of either economic values or social inclinations. Technology that is pertinent to public interest, in this context, will be possible if a social inclination toward public interest can be built. The state can shape a social inclination of the kind and intervene in the mechanism of technology development. Furthermore, such an intervention could be accelerated by the potency of the collective actions of citizens. If successful, technology will incorporate the social value of public interest and the paradigm of technology will embrace it. Survey responses indicated that the biggest misconception of technology was in the concept of technological knowledge, which especially was supposed to be distinguished from scientific knowledge; technology was perceived to have a distinctive kind of knowledge and to be practical, but still to be a part of science pursuing the knowledge of nature. Technology still seemed to be a mere part of science with more emphasis on practical purpose in everyday life, which was concurred with the term applied science. The respondents agreed on the idea of value-ladeness of technology and, thus, necessity for human control over technology. However, they appeared to have relatively passive attitudes toward technology. The conflict between the necessity for control and the paucity of faith in the ability to control technology by themselves must attribute respondents’ dependency toward experts. The correlation between understanding of technology and will to control technology was statistically significant but weak. The control variables of academic affiliation and department were found to have significant effects on the results

Control systems for function restoration, exercise, fitness and health in spinal cord injury

We describe original research contributions to the engineering development of systems which aim to restore function and enable effective exercise for people with spinal cord injury (SCI). Our work utilises functional electrical stimulation (FES) of paralysed muscle. Improving function and general health through participation in exercise is vital to the enhancement of quality of life, well-being and promotion of longevity. Crucial to the development of this research has been judicious use of advanced methods of feedback control engineering; this has been a key enabling factor in many of our original contributions. The consequences of a spinal cord injury can be severe. The primary effects may include; paralysis and loss of sensation in the legs, arms and trunk; disruption of bladder and bowel function; and disruption of the autonomic regulation of blood pressure, heart rate and lung function. If the abdominal and chest muscles are paralysed, breathing will be compromised, and patients with a high-level cervical injury may require mechanical ventilation. These primary effects of a spinal cord injury may, over time, lead to a range of debilitating secondary medical complications. These include reduced cardiovascular fitness, urinary tract infection and an associated risk of kidney disease, reduced bone mineral density, the possible development of pressure sores, and muscle spasticity. People with paralysed chest and abdominal muscles are at increased risk of respiratory infection. Consideration of these factors has led us to focus our research programme in this field on novel engineering solutions which have relevance to the secondary consequences of spinal cord injury, and which may help to alleviate some of their effects. In this thesis we describe our contributions in the following areas: 1. Control of Paraplegic Standing; This work concerns upright stance, and aims to provide; (i) automatic feedback control of balance during stance, with the arms free for functional tasks; (ii) methods and apparatus for dynamic standing therapy, which may help to enhance the individual's retained balance skills. This area of work has successfully demonstrated the automatic control of balance during quiet standing in paraplegic subjects. Further, we have established the feasibility of ankle stiffness control in paraplegic subjects using FES, and we have shown that this can be combined with volitional upper-body inputs to achieve stable, arm-free balance. 2. Lower-limb Cycling: Lower-limb cycling, achieved through electrical stimulation of paralysed leg-actuating muscles, is an effective exercise intervention. We have described refinements to the engineering design of an FES-cycling system, based upon the adaptation of commercially-available recumbent tricycles (of various designs), some of which are equipped with an auxiliary electric motor. We have contributed new methods of feedback control of key variables including cycle cadence and exercise workrate. These contributions have facilitated further detailed study of the effect of the exercise on cardiopulmonary fitness, bone integrity, spasticity, muscle condition, and factors relating to the likelihood of skin breakdown (i.e. the development of pressure sores). 3. Upper-limb Exercise in Tetraplegia; We have developed a new exercise modality for patients with a cervical-level injury and significant loss of arm function. The system allows effective arm ergometry by combining volitional motion with electrical stimulation of the paralysed upper-arm muscles. This work has developed new apparatus and exercise testing protocols, and has examined the effect of the exercise on cardiopulmonary fitness and muscle strength in experiments with tetraplegic subjects. 4. Modelling and Control of Stimulated Muscle; This fundamental area of research has investigated dynamic modelling and feedback control design approaches for electrically-stimulated muscle. This work has been applied in the three areas mentioned above. We identify promising areas for future research. These include extension of work on lower- limb cycling to patients with incomplete injuries, to those with cervical-level injuries, and to children with SCI. We wish to participate in a multi-centre clinical study of implanted nerve- root stimulation technology for restoration of bladder and bowel control, and for lower-limb exercise (including cycling). We have initiated a study of treadmill-based gait therapy for incomplete-lesion patients. The goals of this study are to develop test protocols for accurate characterisation of cardiopulmonary status, and to determine whether this form of cyclical lower-limb exercise has a positive impact on retained voluntary leg function. It is often the case that it is those people most severely affected by neurological impairment who stand to gain the most from these approaches (e.g. high-level tetraplegia, paediatric spinal cord injury, etc.). We must therefore continue to seek ways in which the work can be developed for the maximum benefit of these patients. In conclusion, this thesis has described original research contributions to the engineering development of systems which aim to restore important function and to enable effective exercise for people with spinal cord injury. An important facet of our work has been the application of feedback control methods; this has been an enabling factor in several areas of study. We have focused on areas which promise improved fitness and general health, and which may alleviate some of the secondary consequences of spinal cord injury. This work encompasses fundamental research, clinical studies, and the pursuit of technology transfer into clinical practice. Finally, we recognise the growing awareness of and interest in central nervous system plasticity, and in the broad field of central neural regeneration and repair. It is therefore timely to ask whether cyclical exercise interventions can lead to improvement of volitional function in patients with incomplete or discomplete lesions. Such improvements may, we speculate, result from the strengthening of muscles which retain at least partial volitional control, or from neural plasticity and re-organisation, or from regeneration effects (neurogenesis and functional connectivity). A key requirement in this line of investigation, and a major challenge, will be to develop or to utilise methods which can detect changes in a patient's volitional function and neurological status, and which can isolate the source of such changes. Should reliable methods become available, the way to the study of recovery of function through cyclical exercise would be opened. These considerations will remain, we propose, an indispensable complement to cell-based surgical interventions which may become available in the future