GT Neuro Seminar Series

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Now showing 1 - 10 of 119
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    Themes and Variations in Animal Behavior
    (Georgia Institute of Technology, 2024-01-29) Berman, Gordon
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    Functionally Stratified Encoding in a Biological Gyroscope
    (Georgia Institute of Technology, 2023-10-02) Dickerson, Bradley H.
    Flies are among nature’s most agile flying creatures. This exquisite maneuverability is due in part to their possession of specialized mechanosensory organs known as the halteres. The halteres are evolved from the hindwings and provide flies with dynamic mechanosensory feedback on a wingstroke-to-wingstroke basis. Additionally, halteres are biological “gyroscopes;” they rapidly detect rotational perturbations and help flies maintain a stable gaze and flight posture. Thus, the halteres serve as multifunctional sensory structures that provide essential timing information to the flight circuit. Halteres are covered in arrays of mechanosensors known as campaniform sensilla, that are arranged in distinct groups. Although longstanding hypotheses suggest that these different arrays may provide different information relevant to flight control, we know little about how haltere sensor location maps to physiology and behavior. I will discuss ongoing work in which we use a genetically encoded calcium indicator to visualize activity changes in the mechanosensors embedded in the haltere during active, visually mediated flight. I will also address how we are exploring the mechanisms by which mechanosensory input is recruited using reverse correlation analysis. Finally, I will cover our initial forays into connectomics and our development of an atlas describing the structure-function relationship between rapid mechanosensory feedback and motor systems.
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    Connectomic Deep Brain Stimulation
    ( 2023-04-24) McIntyre, Cameron
    Deep brain stimulation (DBS) is an established clinical therapy for the treatment of movement disorders, and evolving to become a viable clinical option for the treatment of psychiatric disorders. In either case, current scientific understanding suggests that the mechanisms of DBS therapy are rooted in the disruption of pathologic brain network activity. In parallel, MRI-based modeling of the human brain structural connectome have facilitated the development of computational strategies to simulate the network effects of DBS on a patient-specific basis, and in turn advance understanding of the pathologic circuits underlying the symptoms. In addition, connectomic DBS models can be used to guide surgical planning and/or stimulation parameter customization. This presentation will describe the evolution of connectomic DBS concepts and methods, and present examples of their application in clinical research studies.
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    Perception in Action: Neural Circuits for Active Auditory and Tactile Decision-making
    ( 2023-04-17) Rodgers, Chris
    How do we explore and learn about our world? In nature, animals do not passively await stimuli, as they typically must do in the laboratory. Instead, they actively seek out sensory information—for instance, to find food or shelter. I will first present a summary of my postdoctoral work, which showed how mice recognize different shapes using their whiskers. We used a new method called behavioral decoding to show what sensorimotor strategies mice used to recognize shapes, and we identified an efficient formatting for those strategies in somatosensory cortex. Next, I will present new work from my own lab. We have developed an active sound-seeking task for mice, in which they use head and body movements to find sound sources. We hypothesize that sensory and motor brain regions exchange predictive signals to compute how best to move the body to localize the sound. In future work we plan to identify how central sensorimotor plasticity enables resilience to sensory loss, with the ultimate goal of rationally engineering neural interventions to restore healthy sensorimotor function.
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    Combining Transcranial Brain Stimulation with Neuroimaging for State-dependent Stimulation and Causal Network Interrogation
    ( 2023-03-27) Bergmann, Til Ole
    Functional neuroimaging and electrophysiological techniques, such as functional magnetic resonance imaging (fMRI) as well as electro- and magnetoencephalography (EEG/MEG), serve well to study spontaneous or task-related neuronal activity as correlates of specific cognitive functions in the human brain. However, to infer causality of brain activation for cognition, the former must be manipulated experimentally. This is possible in healthy humans with the help of non-invasive brain stimulation (NIBS) techniques, such as transcranial magnetic stimulation (TMS), transcranial electric stimulation (tES), and since recently also transcranial ultrasound stimulation (TUS). Importantly, NIBS can also be combined with fMRI as well as EEG/MEG, either concurrently (online) or consecutively (offline). Online approaches, assessing the immediate neural response to stimulation, can be used to (i) quantify neuronal network properties such as excitation, inhibition, or connectivity, (ii) interfere with ongoing spontaneous or task-related activity and thus affect behavioral performance, or (iii) modulate the level and timing of neuronal activity, e.g., trying to mimic neuronal oscillations in behaviorally relevant manner. In contrast, offline approaches can be utilized to either (iv) inhibit or (v) facilitate local neuronal excitability via the induction of synaptic plasticity, assessing its subsequent effects on neuronal activity and behavior. In this talk, I will discuss the different approaches and challenges with respect to their combination with fMRI and EEG, in particular concurrent TMS-fMRI and TMS-EEG, and highlight their potential as well as the caveats for inferring causality from NIBS studies in cognitive neuroscience. I will also introduce the novel approach of brain state-dependent brain stimulation, which allows to control NIBS in real-time based on the online assessment of specific oscillatory states, providing a unique opportunity to causally interact with ongoing neuronal oscillations to study its role in information processing and synaptic plasticity.
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    Scalable Human Brain Imaging with Time-of-flight Filtered Diffuse Optical Interferometry
    ( 2023-03-06) Srinivasan, Vivek
    Our group develops new light-based technologies for in vivo imaging and sensing of the brain and eye, with the goal of understanding what goes wrong in disease and detecting it earlier. Starting with a firm grounding in neurophysiology and biomedical engineering, we employ ideas and technologies from fields including telecommunications and photonic sensing to accomplish this goal.
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    Neural Circuits for Vision in the Natural World
    ( 2023-02-27) Niell, Cristopher
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    Reconnecting the Hand and Arm to the Brain (ReHAB): Bi-directional Neuroprostheses for Sensorimotor Functional Restoration
    ( 2023-02-14) Ajiboye, A. Bolu
    Cortically controlled neuroprostheses have long been posited as the “holy grail” for intracortical brain-machine interfaces (BMIs). The efficacy of BMIs has advanced to the point where a small number of laboratories around the US now run human clinical trials with people with chronic paralysis. As part of the ReHAB Clinical Trial, my Laboratory for Intelligent Machine-Brain Systems (LIMBS) investigates using BMIs to control Functional Electrical Stimulation (FES) systems for restoring reach-to-grasp movements to persons with chronic high cervical spinal cord injury. This lecture will discuss several of our clinical, technological, and scientific advances towards developing a bi-directional BMI controlled FES arm neuroprosthesis for restoring motor and somatosensory function. The highlight of this lecture will be the demonstration of a current ReHAB participant, an individual with chronic tetraplegia, eight years post-injury using a multi-nodal BMI with multi-contact FES nerve cuff electrodes to volitionally and independently perform functional tasks, such as self-feeding and shaking hands, and discerning somatosensory feedback through intracortical microstimulation (ICMS). This lecture will also discuss use of human BMI systems as a platform for interrogating fundamental questions of human sensorimotor control, including understanding underlying mechanisms of motor performance and learning, and internal representations of kinetic, kinematic, and somatosensory parameters. Finally, this lecture will discuss steps towards clinical translation of viable FES+BMI neuroprosthetic systems for potential at-home use.
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    Predictive processing in cortical and cerebellar circuits
    ( 2023-02-06) Najafi, Farzaneh
    Predictive coding is a theory of brain function that assumes the brain contains an internal model of the world, which constantly generates predictions about our environment, and updates the predictions if they deviate from the actual external inputs. Impaired predictive processing is suggested to underlie symptoms such as hallucinations and social disconnection in neurological disorders such as schizophrenia and autism. Treating these disorders requires understanding the neural mechanisms that generate and update prediction signals in the healthy brain. My long-term vision is to shed light on the circuits and computations that underlie predictive processing in the brain. I will start my talk by presenting data from my previous research that demonstrate predictive signals in cortical and cerebellar circuits in behaving mice. Then I will describe the gap in our knowledge about how the cerebellum and cortex may interact to support predictive behavior. Finally, I will present the future research plans for my lab to investigate these unknown questions, shedding light on the cortico-cerebellar circuitries that underlie predictive processing.