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3 Janelia Publications

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    Magee Lab
    08/01/10 | Network mechanisms of theta related neuronal activity in hippocampal CA1 pyramidal neurons.
    Losonczy A, Zemelman BV, Vaziri A, Magee JC
    Nature Neuroscience. 2010 Aug;13(8):967-72. doi: 10.1038/nn.2597

    Although hippocampal theta oscillations represent a prime example of temporal coding in the mammalian brain, little is known about the specific biophysical mechanisms. Intracellular recordings support a particular abstract oscillatory interference model of hippocampal theta activity, the soma-dendrite interference model. To gain insight into the cellular and circuit level mechanisms of theta activity, we implemented a similar form of interference using the actual hippocampal network in mice in vitro. We found that pairing increasing levels of phasic dendritic excitation with phasic stimulation of perisomatic projecting inhibitory interneurons induced a somatic polarization and action potential timing profile that reproduced most common features. Alterations in the temporal profile of inhibition were required to fully capture all features. These data suggest that theta-related place cell activity is generated through an interaction between a phasic dendritic excitation and a phasic perisomatic shunting inhibition delivered by interneurons, a subset of which undergo activity-dependent presynaptic modulation.

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    Magee Lab
    06/29/10 | Two-photon single-cell optogenetic control of neuronal activity by sculpted light.
    Andrasfalvy BK, Zemelman BV, Tang J, Vaziri A
    Proceedings of the National Academy of Sciences of the United States of America. 2010 Jun 29;107(26):11981-6. doi: 10.1073/pnas.1006620107

    Recent advances in optogenetic techniques have generated new tools for controlling neuronal activity, with a wide range of neuroscience applications. The most commonly used approach has been the optical activation of the light-gated ion channel channelrhodopsin-2 (ChR2). However, targeted single-cell-level optogenetic activation with temporal precessions comparable to the spike timing remained challenging. Here we report fast (< or = 1 ms), selective, and targeted control of neuronal activity with single-cell resolution in hippocampal slices. Using temporally focused laser pulses (TEFO) for which the axial beam profile can be controlled independently of its lateral distribution, large numbers of channels on individual neurons can be excited simultaneously, leading to strong (up to 15 mV) and fast (< or = 1 ms) depolarizations. Furthermore, we demonstrated selective activation of cellular compartments, such as dendrites and large presynaptic terminals, at depths up to 150 microm. The demonstrated spatiotemporal resolution and the selectivity provided by TEFO allow manipulation of neuronal activity, with a large number of applications in studies of neuronal microcircuit function in vitro and in vivo.

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    Magee LabHarris Lab
    06/01/10 | Multi-array silicon probes with integrated optical fibers: light-assisted perturbation and recording of local neural circuits in the behaving animal.
    Royer S, Zemelman BV, Barbic M, Losonczy A, Buzsáki G, Magee JC
    The European Journal of Neuroscience. 2010 Jun;31:2279-91. doi: 10.1002/cbic.201000254

    Recordings of large neuronal ensembles and neural stimulation of high spatial and temporal precision are important requisites for studying the real-time dynamics of neural networks. Multiple-shank silicon probes enable large-scale monitoring of individual neurons. Optical stimulation of genetically targeted neurons expressing light-sensitive channels or other fast (milliseconds) actuators offers the means for controlled perturbation of local circuits. Here we describe a method to equip the shanks of silicon probes with micron-scale light guides for allowing the simultaneous use of the two approaches. We then show illustrative examples of how these compact hybrid electrodes can be used in probing local circuits in behaving rats and mice. A key advantage of these devices is the enhanced spatial precision of stimulation that is achieved by delivering light close to the recording sites of the probe. When paired with the expression of light-sensitive actuators within genetically specified neuronal populations, these devices allow the relatively straightforward and interpretable manipulation of network activity.

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