GT Neuro Seminar Series

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Now showing 1 - 10 of 61
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    Evolution and Development of a Minimal Nervous System in our Closest Invertebrate Relatives
    ( 2019-11-25) Stolfi, Alberto
    Animal behavior depends both on the intrinsic properties of individual neurons and how these neurons connect to and modulate one another. A major focus of modern neuroscience is to dissect behavior at the level of individual genes, neurons, and specific synaptic connections, but we are far from fully understanding how the composition and connectivity of even the smallest nervous systems can determine the wide range of behaviors observed in a free-living animal. Our lab is investigating the development of the simple larval nervous systems of tunicates like Ciona, marine invertebrates closely related to vertebrates. Although tunicates are chordates like us, Ciona larvae possess the smallest nervous system ever described at only 231 total neurons (177 central nervous system neurons and 54 peripheral sensory cells), comprising only the second complete “connectome” ever mapped. Using experimental tools such as CRISPR/Cas9-mediated mutagenesis and single-cell RNAseq, we have uncovered neurodevelopmental processes that shape this minimal nervous system, some of which are conserved even in mammals. We are also interested in studying an even more extreme example of the “minimization” of the tunicate nervous system, focusing on certain species that bypass the swimming larval phase and are therefore undergoing evolutionary loss of the larval nervous system altogether.
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    Two Forms of Plasticity in Adult Visual Cortex
    ( 2019-11-18) Stryker, Michael P.
    Michael Stryker's laboratory studies the development and plasticity of the central visual system. Most of his laboratory's effort focuses on the role of neural activity in the primary visual cortex of the mouse, where they have identified a circuit that dramatically enhances activity-dependent plasticity in adult animals. They use 2-photon microscopy and electrophysiology to study genetically identified types of neurons in alert animals. His laboratory's major interest is the in the mechanisms responsible for the development and plasticity of precise connections within the central nervous system, and particularly in the role of neural activity in this process. Most of the work performed is on the visual cortex of the mouse. In normal development, neural connections to and within the visual cortex are refined to high precision through the action of activity-dependent mechanisms of neural plasticity in combination with specific molecular signals. In experiments, the lab induces activity-dependent plasticity experimentally through manipulations of genetics or experience or by pharmacological or neurophysiological intervention in order to discover what cellular mechanisms and what changes in cortical circuitry are responsible for rapid, long lasting changes in neuronal responses. These changes are analyzed using microelectrode recordings, novel techniques for measurement of optical and metabolic signals related to neural activity, including 2-photon microscopy and intrinsic signal imaging, and anatomical and neurochemical tracing of connections.
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    Neural Decoding and Control of Multiscale Brain Networks: From Motor to Mood
    ( 2019-11-11) Shanechi, Maryam
    In this talk, I first discuss our recent work on modeling, decoding, and controlling multisite human brain activity underlying mood states. I present a multiscale dynamical modeling framework that allows us, for the first time, to decode mood variations and identify brain sites that are most predictive of mood. I then develop a system identification approach that can predict large-scale brain network dynamics (output) in response to electrical stimulation (input) to enable closed-loop control of brain activity. Finally, I demonstrate that our modeling framework can uncover multiscale neural dynamics from hybrid spike-field activity in monkeys performing unconstrained movements and can further combine information from multiple scales of activity and model their different time-scales and statistical profiles. These models, decoders, and controllers could facilitate future closed-loop therapies for neurological and neuropsychiatric disorders and help probe neural circuits.
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    Where Brain, Machine, and Mind Collide
    ( 2019-11-06) Batista, Aaron ; Jung, Ranu ; Kemere, Caleb ; Rommelfanger, Karen ; Yu, Byron
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    Epilepsy – Beyond the Local Network
    ( 2019-10-28) Pedersen, Nigel
    While human research has emphasized the large-scale network disruptions in the epilepsies and their co-morbidities, basic science has typically focused on local networks. In rodents, more general large-scale network dynamics are essentially unstudied at fast time scales and high spatial precision. I will describe our human work examining forebrain connectivity and animal studies that examine large scale network manipulations and the development of techniques to record from larger anatomically connected networks. Present animal model work focuses on manipulations of one of the most important large-scale networks - the major state control system for sleep-wake and vigilance. While these circuits have been elucidated in increasing detail over the last decade and are the major controller of brain rhythms and excitability, they are surprisingly little explored in epilepsy. I will discuss the limitations of present technologies for studying large-scale brain networks in rodents and a solution that we are developing.
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    Evolutionarily Conserved Mechanisms of Sociality
    ( 2019-10-07) Kelly, Aubrey
    There is an extraordinary amount of variation in social behavior within and across species. However, when phenotypic convergence in behavior (e.g., sociality) is observed, it begs the question as to whether the same neural mechanisms evolved across species to promote sociality, or whether they have reached a similar behavioral endpoint via different modifications to the brain. In this talk, I will focus on a neural system that is well known for modulating numerous types of social behavior – the nonapeptide system. The nonapeptides, vasopressin and oxytocin, are produced in distinct neuronal populations throughout the brain, with each population having distinct, yet some overlapping, behavioral functions. Using correlational and causal studies in birds and rodents, I will demonstrate evolutionarily conserved prosocial and anti-aggressive functions of a nonapeptide subcircuit originating in the extended medial amygdala. This research highlights the importance of utilizing a comparative approach, which can allow us to identify fundamental core principles of brain organization that allow an animal to be social.
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    Perturbation-imaging Approaches to Study Functional Contributions of Cortical Activity to Human Movement
    ( 2019-09-30) Borich, Michael
    The ability to learn and produce skilled movements is required for humans to successfully engage with each other and their environment. A principal role of the brain is to guide current, and plan future, movements based on past actions and potential rewards. In this talk, I will describe ongoing work in our lab employing multiple approaches to investigate the functional contributions of brain activity to normal and abnormal human movement. I will discuss how transcranial magnetic stimulation (TMS), a form of non-invasive brain stimulation, can be used both characterize and modulate cortical activity and connectivity during movement. I will also describe our recent findings showing abnormal TMS-evoked cortical reactivity post-stroke that is related to persistent paretic arm impairment. Lastly, I will discuss preliminary work applying alternative perturbation paradigms to study brain-behavior relationships in health and disease.
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    Using Human Brain Organoids to Unveil Neuron-Glial Interactions During Development
    ( 2019-09-23) Sloan, Steven A.
    Glia are the most abundant cell types in the mammalian nervous system. They are integral to normal brain physiology, yet we still understand very little about what functions they perform, how they develop, and how they are involved in disease. We understand even less about these cells in humans because of the lack of direct access to intact, functioning human brain tissue. Our lab is using pluripotent stem cells (iPSCs) derived non-invasively from skin samples to generate brain cells in the lab. Because the brain is a 3D structure and studying cells growing on a plate does not recapitulate its complexity, we are using human iPSCs to generate functional 3D structures that are patterned to mirror specific regions of the human brain. We can culture these 'brains-in-a-dish' for long periods of time to ask how normal brain development is occurring in a human system. Additionally, this method allows us to ask questions about how neurons and glia interact with each other in both healthy and diseased contexts, and to manipulate specific variables of brain development in an otherwise complex developmental system.
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    Functional Imaging of the Human Brain: A Window into the Architecture of the Mind
    ( 2019-09-16) Kanwisher, Nancy
    The last 20 years of brain imaging research has revealed the functional organization of the human brain in glorious detail, including dozens of cortical regions each of which is specifically engaged in a particular mental task, like recognizing faces, perceiving speech sounds, and understanding the meaning of a sentence. Each of these regions is present, in approximately the same location, in every normal person. This initial rough sketch of the functional organization of the brain counts as real progress, giving us a kind of diagram of the major components of the human mind. But at the same time, it is just the barest beginning. Really what our new map of the human brain offers is a vast landscape of new questions. In this talk I will first broadly survey some of the most widely replicated functionally distinctive cortical regions, and then describe ongoing work into three such questions. First, in light of widespread findings that functionally specific cortical regions contain information about “nonpreferred” stimuli, do some patches of cortex really play a highly specific causal role in processing just one class of stimuli? Second, how does all this complex structure, that is so similar across subjects, arise in development? I will discuss the developmental origins of cortical specificity, including a new finding of what appears to be a fusiform face area in the ventral visual pathway of congenitally blind people. Third, why do we have the particular functionally specific cortical regions we do, and apparently not others, and why, from a computational point of view, is functional specificity a good design feature for brains in the first place?
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    Neural Mechanisms of Movement Precision
    ( 2019-09-09) Person, Abigail
    How the brain makes movements fast, smooth and accurate has remained a mystery. In this talk I will discuss our studies identifying predictive, adaptively scaled activity in a cerebellar output structure that causally controls limb velocity to enhance movement precision. The data have implications into the fundamental algorithms of the cerebellum and suggest loci for interventions in motor disorders.