Characterizing motor control signals in the spinal cord

The main goal of this project is to develop a rodent model to study the central command signals generated in the brain and spinal cord for the control of motor function in the forearms. The nature of the central command signal has been debated for many decades with only limited progress. This thesis presents a project that investigated this problem using novel techniques. Rats are instrumented to record the control signals in their spinal cord while they are performing lever press task they are trained in. A haptic interface and wireless neural data amplifier system simultaneously collects dynamic and neural data. Isometric force is predicted from force signal using a combination of time-frequency analysis, Principle component analysis and linear filters. Neural-force mapping obtained at one location are subsequently applied to isometric data recorded at other locations. Prediction errors exhibited negative relationship with the isometric position at upper half of movement range. This suggests the presence of restorative forces which are consistent with positional feedback at spinal level. The animal also appears to become unstable in the lower half of their movement ranges, likely caused by a transition from bipedal to quadruped posture. The presence of local feedback and ability for animals to plan postures that are unstable in absence of external forces suggest that descending signal is a reference trajectory planned using internal models. This has important consequences in design of neuroprosthetic actuators: Inverse dynamic models of patient limbs and local positional feedbacks can improve their performance

Investigating the Effects of a Task-Specific Fatigue Protocol on Hand Tracking Performance Using a Wrist Robotic Device

The purpose of this work was to evaluate the effects of a dynamic submaximal fatigue protocol and forearm/hand anthropometrics on hand tracking performance. Participants traced a 2:3 Lissajous curve using a haptic wrist robotic device (WristBot). This same curve was traced before the fatigue (baseline), during the fatigue protocol, and after the fatigue protocol. Post fatigue trials were completed at 0, 1, 2, 4, 6, 8, and 10 minutes after the cessation of the fatigue protocol. Overall tracking performance and movement smoothness decreased immediately. Directional biases in the normal and longitudinal component of tracking error were present after the fatigue protocol. Proximal forearm circumference and forearm length had a negative correlation with movement smoothness. Hand tracking performance decreased due to the submaximal fatigue protocol. Those with a larger proximal forearm circumference and longer forearm length had better movement smoothness performance which can be applied to the workplace where hand and wrist are predominately used

Study and development of sensorimotor interfaces for robotic human augmentation

This thesis presents my research contribution to robotics and haptics in the context of human augmentation. In particular, in this document, we are interested in bodily or sensorimotor augmentation, thus the augmentation of humans by supernumerary robotic limbs (SRL). The field of sensorimotor augmentation is new in robotics and thanks to the combination with neuroscience, great leaps forward have already been made in the past 10 years. All of the research work I produced during my Ph.D. focused on the development and study of fundamental technology for human augmentation by robotics: the sensorimotor interface. This new concept is born to indicate a wearable device which has two main purposes, the first is to extract the input generated by the movement of the user's body, and the second to provide the somatosensory system of the user with an haptic feedback. This thesis starts with an exploratory study of integration between robotic and haptic devices, intending to combine state-of-the-art devices. This allowed us to realize that we still need to understand how to improve the interface that will allow us to feel the agency when using an augmentative robot. At this point, the path of this thesis forks into two alternative ways that have been adopted to improve the interaction between the human and the robot. In this regard, the first path we presented tackles two aspects conerning the haptic feedback of sensorimotor interfaces, which are the choice of the positioning and the effectiveness of the discrete haptic feedback. In the second way we attempted to lighten a supernumerary finger, focusing on the agility of use and the lightness of the device. One of the main findings of this thesis is that haptic feedback is considered to be helpful by stroke patients, but this does not mitigate the fact that the cumbersomeness of the devices is a deterrent to their use. Preliminary results here presented show that both the path we chose to improve sensorimotor augmentation worked: the presence of the haptic feedback improves the performance of sensorimotor interfaces, the co-positioning of haptic feedback and the input taken from the human body can improve the effectiveness of these interfaces, and creating a lightweight version of a SRL is a viable solution for recovering the grasping function

Design and effectiveness evaluation of mirror myoelectric interfaces: a novel method to restore movement in hemiplegic patients

The motor impairment occurring after a stroke is characterized by pathological muscle activation patterns or synergies. However, while robot-aided myoelectric interfaces have been proposed for stroke rehabilitation, they do not address this issue, which might result in inefficient interventions. Here, we present a novel paradigm that relies on the correction of the pathological muscle activity as a way to elicit rehabilitation, even in patients with complete paralysis. Previous studies demonstrated that there are no substantial inter-limb differences in the muscle synergy organization of healthy individuals. We propose building a subject-specific model of muscle activity from the healthy limb and mirroring it to use it as a learning tool for the patient to reproduce the same healthy myoelectric patterns on the paretic limb during functional task training. Here, we aim at understanding how this myoelectric model, which translates muscle activity into continuous movements of a 7-degree of freedom upper limb exoskeleton, could transfer between sessions, arms and tasks. The experiments with 8 healthy individuals and 2 chronic stroke patients proved the feasibility and effectiveness of such myoelectric interface. We anticipate the proposed method to become an efficient strategy for the correction of maladaptive muscle activity and the rehabilitation of stroke patients.This study was funded by the Baden-Württemberg Stiftung (GRUENS ROB-1), the Deutsche Forschungsgemeinschaft (DFG, Koselleck), the Fortüne-Program of the University of Tübingen (2422-0-0), and the Bundes Ministerium für Bildung und Forschung BMBF MOTORBIC (FKZ 13GW0053), AMORSA (FKZ 16SV7754), Gipuzkoa Regional Government (INKRATEK), Ministry of Science of the Basque Country (Elkartek: EXOTEK). A. Sarasola-Sanz’s work was supported by La Caixa-DAAD scholarship and N. Irastorza-Landa’s work by the Basque Government and IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

Of Mice and Men: An Ergonomic and Market Assessment of Current Computer Mice

Gemstone Team MICE (Modifying and Improving Computer Ergonomics)Work-related Musculoskeletal Disorders (WMSDs) are conditions that develop over time due to repetitive motion and can painfully affect the fingers, wrist, arm, shoulder, back, and neck. Studies indicate a correlation between heavy computer mouse use and the prevalence of WMSDs. Our team evaluated current ergonomic mouse designs to determine which features of mice reduce excessive muscle activation and harmful arm and hand positioning while still maintaining ease of use and marketability. A motion capture system tracked arm and hand positioning, EMG analysis measured muscle activation, force sensors quantified the user‘s clicking force, and a Fitts‘ test evaluated mouse use efficiency. To determine the marketability of mice features, surveys generalized user preferences, while focus groups closely examined specific market factors. All these systems were combined to identify areas of improvement in ergonomic mouse design

Gaussian process autoregression for simultaneous proportional multi-modal prosthetic control with natural hand kinematics

Matching the dexterity, versatility, and robustness of the human hand is still an unachieved goal in bionics, robotics, and neural engineering. A major limitation for hand prosthetics lies in the challenges of reliably decoding user intention from muscle signals when controlling complex robotic hands. Most of the commercially available prosthetic hands use muscle-related signals to decode a finite number of predefined motions and some offer proportional control of open/close movements of the whole hand. Here, in contrast, we aim to offer users flexible control of individual joints of their artificial hand. We propose a novel framework for decoding neural information that enables a user to independently control 11 joints of the hand in a continuous manner-much like we control our natural hands. Toward this end, we instructed six able-bodied subjects to perform everyday object manipulation tasks combining both dynamic, free movements (e.g., grasping) and isometric force tasks (e.g., squeezing). We recorded the electromyographic and mechanomyographic activities of five extrinsic muscles of the hand in the forearm, while simultaneously monitoring 11 joints of hand and fingers using a sensorized data glove that tracked the joints of the hand. Instead of learning just a direct mapping from current muscle activity to intended hand movement, we formulated a novel autoregressive approach that combines the context of previous hand movements with instantaneous muscle activity to predict future hand movements. Specifically, we evaluated a linear vector autoregressive moving average model with exogenous inputs and a novel Gaussian process (gP) autoregressive framework to learn the continuous mapping from hand joint dynamics and muscle activity to decode intended hand movement. Our gP approach achieves high levels of performance (RMSE of 8°/s and ρ = 0.79). Crucially, we use a small set of sensors that allows us to control a larger set of independently actuated degrees of freedom of a hand. This novel undersensored control is enabled through the combination of nonlinear autoregressive continuous mapping between muscle activity and joint angles. The system evaluates the muscle signals in the context of previous natural hand movements. This enables us to resolve ambiguities in situations, where muscle signals alone cannot determine the correct action as we evaluate the muscle signals in their context of natural hand movements. gP autoregression is a particularly powerful approach which makes not only a prediction based on the context but also represents the associated uncertainty of its predictions, thus enabling the novel notion of risk-based control in neuroprosthetics. Our results suggest that gP autoregressive approaches with exogenous inputs lend themselves for natural, intuitive, and continuous control in neurotechnology, with the particular focus on prosthetic restoration of natural limb function, where high dexterity is required for complex movements

The "Federica" hand: a simple, very efficient prothesis

Hand prostheses partially restore hand appearance and functionalities. Not everyone can afford expensive prostheses and many low-cost prostheses have been proposed. In particular, 3D printers have provided great opportunities by simplifying the manufacturing process and reducing costs. Generally, active prostheses use multiple motors for fingers movement and are controlled by electromyographic (EMG) signals. The "Federica" hand is a single motor prosthesis, equipped with an adaptive grasp and controlled by a force-myographic signal. The "Federica" hand is 3D printed and has an anthropomorphic morphology with five fingers, each consisting of three phalanges. The movement generated by a single servomotor is transmitted to the fingers by inextensible tendons that form a closed chain; practically, no springs are used for passive hand opening. A differential mechanical system simultaneously distributes the motor force in predefined portions on each finger, regardless of their actual positions. Proportional control of hand closure is achieved by measuring the contraction of residual limb muscles by means of a force sensor, replacing the EMG. The electrical current of the servomotor is monitored to provide the user with a sensory feedback of the grip force, through a small vibration motor. A simple Arduino board was adopted as processing unit. The differential mechanism guarantees an efficient transfer of mechanical energy from the motor to the fingers and a secure grasp of any object, regardless of its shape and deformability. The force sensor, being extremely thin, can be easily embedded into the prosthesis socket and positioned on both muscles and tendons; it offers some advantages over the EMG as it does not require any electrical contact or signal processing to extract information about the muscle contraction intensity. The grip speed is high enough to allow the user to grab objects on the fly: from the muscle trigger until to the complete hand closure, "Federica" takes about half a second. The cost of the device is about 100 US$. Preliminary tests carried out on a patient with transcarpal amputation, showed high performances in controlling the prosthesis, after a very rapid training session. The "Federica" hand turned out to be a lightweight, low-cost and extremely efficient prosthesis. The project is intended to be open-source: all the information needed to produce the prosthesis (e.g. CAD files, circuit schematics, software) can be downloaded from a public repository. Thus, allowing everyone to use the "Federica" hand and customize or improve it

Freehand Digital Drawing: a Boost to Creative Design. The Observer's Eye and the Draftsman Brain

[ES] La representación de un proyecto arquitectónico tiene diferentes finalidades, una de las más relevantes es su visualización. El tema de esta tesis es la relación entre el diseñador, su actividad cerebral durante la fase creativa, el proyecto representado y la mente del observador. La pregunta, planteada por arquitectos, diseñadores y académicos en los años ochenta y aún abierta a soluciones estimulantes, es una pregunta bien conocida sobre si la creciente digitalización puede ser perjudicial o beneficiosa para esta relación. Después de un análisis de la imagen en la arquitectura a partir del Renacimiento, informado en la Parte 1, se revisan y discuten las técnicas actuales de representación. La primera pregunta, abordada en la Parte 2, fue si la simulación de la realidad con renderizado de calidad fotográfica garantiza una visualización mejor o peor que una imagen tradicionalmente dibujada a mano. Se elaboró un cuestionario para verificar las características de comunicación y representación de las imágenes producidas con las dos técnicas. Los resultados mostraron que estas dos cualidades estaban más presentes en el caso del dibujo a mano alzada que en los renders fotorrealistas. La Parte 3 se centró en el diseñador y utilizó las herramientas proporcionadas por la neurociencia, a saber, el EEG y las 'respuestas evocadas', para cuantificar la actividad cerebral de alguien que hace un dibujo a mano alzada con respecto a CAD. Dado que la tecnología utilizada nunca antes se había aplicado a un sujeto al realizar un diseño, la investigación se dividió en tres experimentos separados. El primero se dedicó a encontrar una forma confiable de realizar registros durante el movimiento del miembro superior en la ejecución del dibujo; los experimentos segundo y tercero tenían como objetivo el análisis específico de la actividad cerebral que precede y sigue a los movimientos individuales de los signos trazados. Los resultados mostraron que la actividad motora relacionada con el dibujo a mano alzada estuvo acompañada por un aumento en la amplitud de las respuestas electroencefalográficas en comparación con el dibujo con CAD. Este dato es probablemente un importante paso adelante a favor de la hipótesis de que la creatividad también puede mejorarse mediante el movimiento en el dibujo a mano alzada. La conclusión es que las imágenes así dibujadas crean una mejor correspondencia entre el autor y el observador, y que el movimiento y la percepción sensorial de la mano pueden fomentar la creatividad. Recientemente, los avances en la técnica de las tabletas de dibujo han proporcionado una nueva técnica para el dibujo a mano alzada, donde se combina la capacidad de gestión de datos del ordenador con los gestos naturales tradicionalmente ligados al uso del papel y el lápiz. de la tecnología moderna puede fusionar el factor humano junto con las nuevas tecnologías digitales.[CA] La representació d'un projecte arquitectònic té diferents finalitats, una de les més rellevants és la seva visualització. El tema d'aquesta tesi és la relació entre el dissenyador, la seva activitat cerebral durant la fase creativa, el projecte representat i la ment de l'observador. La pregunta, plantejada per arquitectes, dissenyadors i estudiosos als anys vuitanta i encara oberta a solucions estimulants, és una qüestió ben coneguda si augmentar la digitalització pot ser perjudicial o beneficiós per a aquesta relació. Després d'una anàlisi de la imatge en arquitectura a partir del període renaixentista, informada a la part 1, es revisen i discuteixen les tècniques de representació actuals. La primera pregunta, abordada a la part 2, va ser si la simulació de la realitat amb renderització de qualitat fotogràfica garanteix una visualització millor o pitjor que una imatge tradicionalment dibuixada a mà. Es va elaborar un qüestionari per comprovar les característiques de comunicació i representació de les imatges produïdes amb les dues tècniques. Els resultats van mostrar que aquestes dues qualitats estaven més presents en el cas del dibuix a mà alçada que en els renders fotorealistes. La part 3 es va centrar en el dissenyador i va utilitzar les eines proporcionades per la neurociència, és a dir, l'EEG i les 'respostes evocades', per quantificar l'activitat cerebral d'algú que realitza un dibuix a mà alçada respecte al CAD. Com que la tecnologia utilitzada mai abans s'havia aplicat a un tema mentre es feia un disseny, la investigació es va dividir en tres experiments separats. El primer es va dedicar a trobar una manera fiable de fer enregistraments durant el moviment de l'extremitat superior en l'execució del dibuix; el segon i el tercer experiment estaven dirigits a l'anàlisi específica de l'activitat cerebral que precedeix i segueix els moviments individuals dels signes traçats. Els resultats van mostrar que l'activitat motora relacionada amb el dibuix a mà alçada va anar acompanyada d'un augment de l'amplitud de les respostes electroencefalogràfiques en comparació amb el dibuix amb CAD. Aquesta dada és probablement un pas endavant significatiu a favor de la hipòtesi que la creativitat també es pot millorar amb el moviment en el dibuix a mà alçada. La conclusió és que les imatges dibuixades d'aquesta manera creen una millor correspondència entre autor i observador, i que el moviment i la percepció sensorial de la mà poden fomentar la creativitat. Recentment, els avenços en la tècnica de dibuix a tauletes han aportat una nova tècnica de dibuix a mà alçada, on la capacitat de gestió de dades de l'ordinador es combina amb els gestos naturals tradicionalment vinculats a l'ús del paper i el llapis. de la tecnologia moderna pot fusionar el factor humà amb les noves tecnologies digitals.[EN] The representation of an architectural project aims at several intents, one of the most relevant being the visualisation of a design. The subject of this dissertation is therefore the relationship between the draftsman, the creativity of his brain, the represented design, and the mind of the observer. Since the Eighties, architects, designers and scholars wondered whether the current habit of an ever increasing digitalisation could be detrimental or advantageous to such relationship. After an analysis of architectural imaging since the Renaissance, as reported in Part 1, the current techniques are reviewed and discussed. The first question, addressed in Part 2, has been whether the simulation of reality with renders of photographic quality, would relate to the observer better or worse than a traditionally hand drawn image. A questionnaire has been constructed to probe the communication and representation qualities of the images. The results suggested that these two qualities were best represented in the case of freehand drawing compared to photorealistic renders. Part 3 was focused on the designer and used the instruments provided by neuroscience, i.e. the EEG and 'evoked responses', to quantify the brain activity in connection with freehand and CAD drawing. Because the involved technology had never been applied before to a drawing subject, the investigation had to be divided into three separate experiments. The first one was dedicated to finding a reliable way to perform the recordings in subjects who freely moved their arm and hand while drawing. The second and third experiments were aimed at analysing the cerebral activity occurring before and after each drawing movement. All results demonstrated that a larger cerebral activity preceded and followed each movement in freehand drawing compared to CAD design. This finding may be considered a robust step towards the notion that also creativity may consequently be improved. The final conclusion is that the freehand drawn images make a better link between author and observer, and at the same time the very movement and haptic perception of the hand elicit creativity. Indeed, the most recent advances in technology of drawing tablets have provided a new medium for freehand drawing, which can exploit the capacity of data handling of computers with the natural movement of using pencil and paper, ending up in a traditional hand made product. A wise usage of modern technology can therefore merge the human factor with the digital world.Leandri, G. (2022). Freehand Digital Drawing: a Boost to Creative Design. The Observer's Eye and the Draftsman Brain [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/188091TESI