http://precedings.nature.com/users/615c7a5f49a39b1d32dd20e940f28df0/ Documents posted by Michiel Remme Nature Publishing Group en Nature Precedings http://precedings.nature.com/images/header_logo.gif http://precedings.nature.com http://dx.doi.org/10.1038/npre.2009.3335.1 The dendritic tree contributes significantly to the elementary computations a neuron performs while converting its synaptic inputs into action potential output. Traditionally, these computations have been characterized as temporally local, near-instantaneous mappings from the current input of the cell to its current output, brought about by somatic summation of dendritic contributions that are generated in spatially localized functional compartments. However, recent evidence about the presence of oscillations in dendrites suggests a qualitatively different mode of operation: the instantaneous phase of such oscillations can depend on a long history of inputs, and under appropriate conditions, even dendritic oscillators that are remote may interact through synchronization. Here, we develop a mathematical framework to analyze the interactions of local dendritic oscillations, and the way these interactions influence single cell computations. Combining weakly coupled oscillator methods with cable theoretic arguments, we derive phase-locking states for multiple oscillating dendritic compartments. We characterize how the phase-locking properties depend on key parameters of the oscillating dendrite: the electrotonic properties of the (active) dendritic segment, and the intrinsic properties of the dendritic oscillators. As a direct consequence, we show how input to the dendrites can modulate phase-locking behavior and hence global dendritic coherence. In turn, dendritic coherence is able to gate the integration and propagation of synaptic signals to the soma, ultimately leading to an effective control of somatic spike generation. Our results suggest that dendritic oscillations enable the dendritic tree to operate on more global temporal and spatial scales than previously thought. http://dx.doi.org/10.1038/npre.2009.3335.1 Fri, 12 Jun 2009 09:46:16 UTC The role of ongoing dendritic oscillations in single-neuron dynamics doi:10.1038/npre.2009.3335.1 2009-06-17 Boris Gutkin Nature Precedings 2009-06-12T09:46:16Z Manuscript Neuroscience http://creativecommons.org/licenses/by/3.0/ http://dx.doi.org/10.1038/npre.2009.3338.1 The responses of rat medial entorhinal cortical neurons form characteristic grid patterns as a function of the animal’s position. A recent model of grid fields proposes a mechanism based on intrinsic single cell properties. It relies on interference patterns emerging from multiple distinct and independent oscillations maintained in the dendritic tree of the cell. Here we examine the requirements necessary to implement this idealized mechanism in a biophysically realistic model. We find that appropriate grid field-formation by a single cell is exquisitely sensitive to intra-dendritic interactions. Mathematical analysis shows how these effects depend on properties of the dendritic oscillators and the (active) membrane segments that connect them. We provide requirements on the ion channel distributions that would be necessary for grid-fields. We implement these requirements in a compartmental model of a spiny stellate cell. We find that with realistic cell properties the intra-dendritic coupling is insufficiently weak to maintain grid field activity. Rather, the cell acts as a single oscillator as opposed to maintaining several independent oscillators. This work gives explicit requirements for a single cell implementation of grid-field activity and hints at a possible circuit level origin for grid pattern formation. http://dx.doi.org/10.1038/npre.2009.3338.1 Fri, 12 Jun 2009 14:26:51 UTC Requirements for a single cell mechanism of entorhinal “grid field” activity: role of dendritic oscillators and coupling doi:10.1038/npre.2009.3338.1 2009-06-12 Boris S. Gutkin Nature Precedings 2009-06-12T14:26:51Z Poster Neuroscience http://creativecommons.org/licenses/by/3.0/