Ongoing Research
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| Suboptimal sensory processing in autism and Down syndrome | |
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In mental disorders such as Down syndrome and autism, excitatory and inhibitory neural interactions are not properly balanced. Our aim is to understand how such imbalance can lead to abnormal behavior and sensory perception in rodent models of autism and Down syndrome. Based on biomarkers distilled from cortical network dynamics, we will investigate drugs which restore the balance of excitation and inhibition, with the potential to restore normal behavior and sensation. (funding: Arkansas Biosciences Institute)
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| Inhibition and sensory information processing | |
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We're testing the hypothesis that either too much or too little inhibition results in a deviation from optimal sensory information processing. Underlying this hypothesis is the idea that such imbalance results in network dynamics which deviate from criticality. We will use multi-site electrode recordings and monitor behavior in rodents to assess processing of tactile and auditory sensory input.
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| Stimulus evoked and spontaneous neuronal avalanches. | |
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We measured spontaneous activity in eye-attached turtle cortex prep using multi-site electrode recordings and well controlled visual stimuli. We aim to determine 1) if neuronal avalanches exist in turtle cortex and 2) to what extent visual sensory input changes this. (with Ralf Wessel and Jeff Pobst at Washington University, St. Louis)
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| Ongoing neural activity in the cortex |
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Using multi-site extracellular recordings in awake monkeys we showed that particular ensembles of reliably firing neurons underly particular spatial patterns observed in the local field potential. We found that ongoing local field potential patterns could be used to predict the spiking of neuron. However, the spiking patterns of many other neurons could be used to predict a single neuron even better than LFP.
(with D. Plenz and T. Bellay at National Institutes of Health)
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Past Research
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| Information Processing in Cortical Networks | ARTICLE: JNeurosci |
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Based on experiments and information theory we showed that balanced interactions between excitatory (E) and inhibitory (I) neurons in the cortex result in maximized information capacity. We also show that this optimal E/I balance results in minimal information loss between stimulus and response. The project is a
collaboration between University of Maryland and National Institutes of Health with H. Yang, R. Roy, and D. Plenz.
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| Regulation of Neural Synchrony by Excitation and Inhibition | ARTICLE: JNeurosci |
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We studied how the dynamics of phase synchrony in a population of cortical neurons depends in the relative influence of excitatory versus inhibitory signalling. We showed that variability of synchrony is maximized near the onset of synchrony, which occurs for an intermediate level of network excitability. The project was a
collaboration between University of Maryland and National Institutes of Health with H. Yang, R. Roy, and D. Plenz.
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We study the ability of brain circuits in vivo (and in vitro) to process sensory (and electrical) stimuli. We use micro-electrode arrays and network level computer models. We are testing the hypothesis that
a brain operating near the critical point of a phase transition is optimally able to process sensory input. The project is a collaboration between University of Maryland and National Institutes of Health with H. Yang, R. Roy, T. Petermann and D. Plenz. A collaboration with Juan Restrepo and Dan Larremore at U Colorado has shed light on the theoretical underpinnings of this phenomenon.
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| Simultaneous two-photon imaging and MEA recording | ARTICLES: JNM |
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Combined two-photon microscopy and micro-electrode arrays (MEA) recording, by developing a method to remove from the MEA signal the electrical artifact caused by the imaging laser. Used this new method to study spontaneous neural activity in rat cortex slices.
(with D. Plenz and T. Bellay at National Institutes of Health)
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| Smart Particles: Temperature | ARTICLES: PRL RSI |
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We have developed flow tracing particles with on-board temperature sensors and wireless communications systems. We have made measurements of Lagrangian heat transport of thermal plumes in Rayleigh-Benard convection. (with Y. Gasteuil, M. Gibert, and J.-F. Pinton at ENS Lyon)
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Continuous ultrasound and high speed cameras are used to measure the three dimensional trajectory of air bubbles in water. The ultrasound method provides direct and very sensitive velocity measurements. We deduce quantitative measurementsof the forces on the bubbles from the peculiar zigzagging and spiraling bubble trajectories. We have developed a simple dynamical model for these motions based on our measurements. We have also explored viscoelastic effects on these dynamics with bubbles rising in non-Newtonian fluids. (with J.-F. Pinton at ENS Lyon)
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Experimental Model of
Earth's Core |
ARTICLES: PEPI My PhD |
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The motion of the molten iron of Earth's outer core was modelled with a 60 cm diameter, rapidly rotating, spherical convection experiment. The titanium vessel contained 100 liters of molten sodium and rotated at rotation rates up to 30 RPS and sustained up to 5 kW of heat transfer. Our results allowed us to estimate the size of convective velocities, time and length scales, ohmic dissipation, as well as the Rayleigh number for the Earth's outer core. (with D. P. Lathrop at UMD)
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| Magneto-turbulence | ARTICLES: PEPI |
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Molten sodium was driven into a highly turbulent state in the presence of large magnetic fields (up to 0.2 T). As the applied magnetic field is increased, Lorentz forces become large enough to significantly suppress the turbulence. For large enough magnetic fields, instabilities arise in the interactions between the fluid flow and the magnetic field, exhibiting regular patterns in the induced magnetic field. These instabilities may be a laboratory manifestation of the magneto-rotational instability. (with D. R. Sisan & D. P. Lathrop at UMD)
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| Coupled Oscillators | ARTICLES: AJP |
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An experimental array of 10 coupled pendulums with sinusoidal forcing was used to explore the control of chaos in spatially extended systems. It was found that the system behaved chaotically when all the pendulums were identical and could be pushed into a periodic state by randomly adjusting their lengths; adding disorder tames the chaos. (with J. F. Lindner at COW)
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