Network Modeling of Motor Pathways from Neural Recordings

During cued motor tasks, for both speech and limb movement, information propagates from primary sensory areas, to association areas, to primary and supplementary motor and language areas. Through the recent advent of high density recordings at multiple scales, it has become possible to simultaneously observe activity occurring from these disparate regions at varying resolution. Models of brain activity generally used in brain-computer interface (BCI) control do not take into account the global differences in recording site function, or the interactions between them. Through the use of connectivity measures, however, it has been made possible to determine the contribution of individual recording sites to the global activity, as they vary with task progression. This dissertation extends those connectivity models to provide summary information about the importance of individual sites. This is achieved through the application of network measures on the adjacency structure determined by connectivity measures. Similarly, by analyzing the coordinated activity of all of the electrode sites simultaneously during task performance, it is possible to elucidate discrete functional units through clustering analysis of the electrode recordings. In this dissertation, I first describe a BCI system using simple motor movement imagination at single recording sites. I then incorporate connectivity through the use of TV-DBN modeling on higher resolution electrode recordings, specifically electrocorticography (ECoG). I show that PageRank centrality reveals information about task progression and regional specificity which was obscured by direct application of the connectivity measures, due to the combinatorial increase in feature dimensionality. I then show that clustering of ECoG recordings using a method to determine the inherent cluster count algorithmically provides insight into how network involvement in task execution evolves, though in a manner dependent on grid coverage. Finally, I extend clustering analysis to show how individual neurons in motor cortex form distinct functional communities. These communities are shown to be task-specific, suggesting that neurons can form functional units with distinct neural populations across multiple recording sites in a context dependent impermanent manner. This work demonstrates that network measures of connectivity models of neurophysiological recordings are a rich source of information relevant to the field of neuroscience, as well as offering the promise of improved degree-of-freedom and naturalness possible through direct BCI control. These models are shown to be useful at multiple recording scales, from cortical-area level ECoG, to highly localized single unit microelectrode recordings

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

Bidirectional Brain-Machine Interfaces for Modulating Stimulation and Neural Plasticity

In prosthetics, tactile feedback can let us feel how we interact with the environment. Without this, it is extremely difficult to perform a motor task with fine control. The same idea can be applied in the brain-machine interface (BMI), which is an interface that directly connects external devices such as prosthetic limbs to the brain. Bidirectional BMI can deliver a stimulation to the brain as a sensory feedback, which can improve the performance of motor tasks. Such a bidirectional BMI can also serve a different role, if the stimulation encodes different information: if it encodes neural activity from another brain area, for example, then bidirectional BMI can provide a bypass for a damaged neural circuit. This may also affect the neural connectivity, strengthening or weakening the underlying neural connections. In this thesis, we present experiments that explore such applications of bidirectional BMI. First, we describe an experiment for characterizing neural connectivity between different brain areas. We found neural connectivity between supramarginal gyrus (SMG) and PMv (ventral premotor area), and also between anterior intraparietal (AIP) and Brodmann’s area 5 (BA5), characterized by field-field, spike-field, and partial spike-field coherence. Through partial spike-field coherence, we also revealed that the spikes in PMv may drive the activity in SMG, which is obscured in ordinary spike-field coherence. Next, we provide evidence of changes in neural connectivity caused by stimulation in S1. With spike-triggered stimulation, which delivers stimulation in S1 in response to spikes recorded in a selected channel in SMG, we could significantly increase the correlation between SMG and S1, measured by the spike time tilling coefficient (STTC) to avoid dependencies of the correlation on firing rates. Furthermore, we found that not only spike-triggered stimulations, but also random stimulations on multiple channels in S1, can vary partial spike-field coherence in theta and alpha bands within S1; such changes mostly occurred in channel pairs with zero phase difference in partial spike-field coherence. Finally, we demonstrate the possibility of volitional control on stimulation pattern in bidirectional BMI. It is shown that the participants could not only increase or decrease a single-channel firing rate, but also hold the firing rate in a given range, demonstrating a fine control over firing rate. These findings would begin to establish a framework for closed-loop modulation of neural activity with bidirectional BMI and could be used to develop new treatments for neurological damage, such as to promote plasticity in or bridge brain areas affected by stroke.</p

Non-invasive methods to investigate brain function in health and disease

Ph. D.Non-invasive methods to investigate brain function have been used in research laboratories for many decades, however their popularity has increased in recent years given the ease of use and broad application. Such methods have proved valuable in improving our knowledge about numerous areas of basic brain function. Many non-invasive techniques have also been applied to patient groups to allow further identification of pathological mechanisms, but critically a new role has been found for some as biomarkers of disease. Neurodegenerative disease is fast becoming one of the biggest medical problems in the first world. An aging population has caused the relative incidence of many conditions to rise dramatically and studies suggest that this trend will continue. Although our knowledge surrounding these conditions has improved significantly, most remain notoriously difficult to diagnose and to treat. The recent introduction of neuroprotective drugs offers the potential to slow the progression of some diseases. However, to take full advantage of these disease-modifying treatments, administration must occur early in the disease course which fuels the demand for selective and specific diagnostic tests. There is currently a great need to enhance the clinical diagnostic repertoire with reliable, robust and specific biomarkers of neurodegenerative disease. However, careful, rigorous studies are required to validate the use of non-invasive techniques in this role. The same level of care should also be applied to techniques used in basic research; without a fundamental understanding of the mechanisms underpinning these techniques, their utility in the investigation of specific processes or pathways is questionable. This thesis aims to address specific cases to evaluate existing techniques and to screen potential new disease biomarkers