Investigation of the stimulation capabilities of a high-resolution neurorecording probe for the application of closed-loop deep brain stimulation

Deep brain stimulation is an established surgical treatment for several neurological and movement disorders, such as Parkinson's disease, in which electrostimulation is applied to targeted deep nuclei in the basal ganglia through implanted electrode leads. Recent technological improvements in the field have focused on the theoretical advantage of current steering and adaptive (closed-loop) deep brain stimulation. Current steering between several active electrodes would allow for improved accuracy when targeting the desired brain structures. This has the additional benefit of avoiding undesired stimulation of neural tracts that are related to side effects, e.g., internal capsule fibres of passage in subthalamic nucleus deep brain stimulation. Closed-loop deep brain stimulation is based on the premise of continuous recording of a proxy for pathological neural activity (such as beta-band power of measured local field potentials in patients with Parkinson's disease) and accordingly adapting the used stimulus parameters. In this study, we investigate the suitability of an existing highresolution neurorecording probe for high-precision neurostimulation. If a subset of the probe's recording electrodes can be used for stimulation, then the probe would be a suitable candidate for closed-loop deep brain stimulation. A finiteelement model is used to calculate the electric potential, induced by current injection through the high-resolution probe, for different sets of active electrodes. Volumes of activated tissue are calculated and a comparison is made between the highresolution probe and a conventional stimulation lead. We investigate the capability of the probe to shift the volume of activated tissue by steering currents to different sets of active electrodes. Finally, safety limits for the injected current are used to determine the size of the volume in which neurons can be activated with the relatively small electrodes patches on the highresolution probe

De animais a máquinas : humanos tecnicamente melhores nos imaginários de futuro da convergência tecnológica

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Sociais, Departamento de Sociologia, 2020.O tema desta investigação é discutir os imaginários sociais de ciência e tecnologia que emergem a partir da área da neuroengenharia, em sua relação com a Convergência Tecnológica de quatro disciplinas: Nanotecnologia, Biotecnologia, tecnologias da Informação e tecnologias Cognitivas - neurociências- (CT-NBIC). Estas áreas desenvolvem-se e são articuladas por meio de discursos que ressaltam o aprimoramento das capacidades físicas e cognitivas dos seres humanos, com o intuito de construir uma sociedade melhor por meio do progresso científico e tecnológico, nos limites das agendas de pesquisa e desenvolvimento (P&D). Objetivos: Os objetivos nesse cenário, são discutir as implicações éticas, econômicas, políticas e sociais deste modelo de sistema sociotécnico. Nos referimos, tanto as aplicações tecnológicas, quanto as consequências das mesmas na formação dos imaginários sociais, que tipo de relações se estabelecem e como são criadas dentro desse contexto. Conclusão: Concluímos na busca por refletir criticamente sobre as propostas de aprimoramento humano mediado pela tecnologia, que surgem enquanto parte da agenda da Convergência Tecnológica NBIC. No entanto, as propostas de melhoramento humano vão muito além de uma agenda de investigação. Há todo um quadro de referências filosóficas e políticas que defendem o aprimoramento da espécie, vertentes estas que se aliam a movimentos trans-humanistas e pós- humanistas, posições que são ao mesmo tempo éticas, políticas e econômicas. A partir de nossa análise, entendemos que ciência, tecnologia e política estão articuladas, em coprodução, em relação às expectativas de futuros que são esperados ou desejados. Ainda assim, acreditamos que há um espaço de diálogo possível, a partir do qual buscamos abrir propostas para o debate público sobre questões de ciência e tecnologia relacionadas ao aprimoramento da espécie humana.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The subject of this research is to discuss the social imaginaries of science and technology that emerge from the area of neuroengineering in relation with the Technological Convergence of four disciplines: Nanotechnology, Biotechnology, Information technologies and Cognitive technologies -neurosciences- (CT-NBIC). These areas are developed and articulated through discourses that emphasize the enhancement of human physical and cognitive capacities, the intuition it is to build a better society, through the scientific and technological progress, at the limits of the research and development (R&D) agendas. Objectives: The objective in this scenery, is to discuss the ethic, economic, politic and social implications of this model of sociotechnical system. We refer about the technological applications and the consequences of them in the formation of social imaginaries as well as the kind of social relations that are created and established in this context. Conclusion: We conclude looking for critical reflections about the proposals of human enhancement mediated by the technology. That appear as a part of the NBIC technologies agenda. Even so, the proposals of human enhancement go beyond boundaries that an investigation agenda. There is a frame of philosophical and political references that defend the enhancement of the human beings. These currents that ally to the transhumanism and posthumanism movements, positions that are ethic, politic and economic at the same time. From our analysis, we understand that science, technology and politics are articulated, are in co-production, regarding the expected and desired futures. Even so, we believe that there is a space of possible dialog, from which we look to open proposals for the public discussion on questions of science and technology related to enhancement of human beings

The Effects of Intracortical Microstimulation Parameters on Neural Responses

RÉSUMÉ Les microstimulations de tissues nerveux du cerveau sont utilisés dans un grand nombre de prothèses sensorielles, de thérapies cliniques et autres activités de recherche se servant de la stimulation électrique. Actuellement, les paramètres de stimulation sont adaptés à chaque application via des tests itératifs. Les méthodes d'optimisation cherchent à améliorer les stimuli développés pour des objectifs spécifiques de stimulation, mais la compréhension fondamentale de la façon dont les paramètres de stimulation influencent les circuits neuronaux qu’ils activent reste largement incomplète. Ce déficit retarde l'optimisation de protocoles existants et rend le développement de nouvelles applications de stimulation difficile. À ce jour, un certain nombre de dispositifs prothétiques validés dès les années 1970 restent en développement, principalement en raison de l'incapacité de ces dispositifs à communiquer efficacement avec le cerveau. Pour utiliser la stimulation électrique afin de transmettre des messages au système nerveux central, une meilleure conception du patron du signal de stimulation est nécessaire. Dans cette thèse, nous étudions l'influence que chaque paramètre du signal (un courant constant, symétrique carré biphasique) exerce sur les réponses qu'il évoquées au travers des microstimulations de la zone intracorticale caudale du membre antérieur dans le cortex moteur chez le rat. Les paramètres de ce signal sont l'amplitude du courant, la fréquence et la durée d'impulsion, l’intervalle d'interphase et la durée du train. Leurs effets ont été évalués par un examen des réponses électromyographiques évoquées dans les muscles des membres antérieurs du rat en réponse à chaque stimulus. Les principaux résultats décrivent comment chaque paramètre de stimulation influence l'amplitude, la latence d’apparition et la durée de la réponse. Une composante jusque-là inexplorée du signal de la réponse (que nous appelons 'activation résiduelle') est aussi analysée pour la première fois. Les théories quant à l'origine et le mécanisme neuronal sous-jacent de ce phénomène sont proposés et les paramètres de stimulation touchant son apparition, la prévalence et la durée sont décrits. La fiabilité des signaux de stimulation pour évoquer des réponses cohérentes est également évaluée par rapport aux variations de paramètres. Une méthodologie pour la conception optimisée des signaux de stimulation est proposée en utilisant un modèle de calcul simple, représentant les relations d'entrée-sortie entre les paramètres de stimulation et les réponses qu'ils évoquent. Ce modèle utilise une approche de réseau neuronal artificiel et peut être utilisé pour prédire les propriétés de la réponse lorsque les paramètres du stimulus sont connus. Compte tenu de la prévalence de la stimulation cérébrale dans les applications cliniques, de recherche et thérapeutiques, les procédures méthodologiques et de modélisation proposées ont des implications importantes dans l'optimisation des paradigmes de stimulation actuels et le développement de protocoles de stimulation pour de nouvelles applications. ----------ABSTRACT Microstimulation of brain tissue plays a key role in a variety of sensory prosthetics, clinical therapies and research applications. At present, stimulus parameters are tailored to each application via iterative testing. Computational optimization methods seek to improve tried and tested waveforms developed for specific purposes, however the fundamental understanding of how stimulation parameters influence the neural circuits they activate remains widely unknown. This deficit hinders both the optimization of existing protocols and the development of new stimulation applications. To date, a number of prosthetic devices validated as early as the 1970’s linger in the development stages largely due to the inability to effectively interface these devices with the brain. In order to use electrical stimulation to convey messages to the central nervous system, a better understanding of stimulus signal design is required. In this thesis, I investigate the influence that each parameter of the constant-current, symmetric, biphasic square waveform exerts on the responses it evokes through intracortical microstimulation of the caudal forelimb area of the rat motor cortex. The parameters under investigation include the current amplitude, pulse frequency, pulse duration, interphase interval and train duration of the stimulus and effects were assessed by examining the electromyographic responses evoked in the rat forelimb muscles in response to each stimulus. The major findings describe how each parameter of the stimulus signal influences the magnitude, onset latency, and duration of the response. A previously unexplored component of the response signal (which we called ‘residual activation’) is analyzed for the first time. Hypotheses as to the origin and underlying neural mechanism of this phenomenon are proposed and the stimulus parameters affecting its occurrence, prevalence and duration are described. The reliability of stimulation signals for evoking consistent responses is also assessed with respect to parameter variations. A methodology for the informed design of stimulation signals is proposed and aided by the development of a simple computational model representing the input-output relationships between stimulation parameters and the responses they evoke. This model uses an artificial neural network approach and can be used to predict the properties of the response when the parameters of the stimulus are known. Given the prevalence of brain stimulation in clinical, research and therapeutic applications the proposed methodological and modeling procedures have important implications in the optimization of current stimulation paradigms and the development of stimulation protocols for new applications