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• Long-Term Potentiation in Rat Hippocampal Neurons Is Accompa...

  Long-Term Potentiation in Rat Hippocampal Neurons Is Accompanied by Spatially Widespread Changes in Intrinsic Oscillatory Dynamics and Excitability Neuron, Volume 56, Issue 6, 20 December 2007, Pages 1061-1075 Rishikesh Narayanan and Daniel Johnston Summary Oscillations in neural activity are a prominent feature of many brain states. Individual hippocampal neurons exhibit intrinsic membrane potential oscillations and intrinsic resonance in the theta frequency range. We found that the subthreshold resonance frequency of CA1 pyramidal neurons was location dependent, varying more than 3-fold between the soma and the distal dendrites. Furthermore, activity- and NMDA-receptor-dependent long-term plasticity increased this resonance frequency through changes in channel properties. The increase in resonance frequency and an associated reduction in excitability were nearly identical in the soma and the first 300 μm of the apical dendrites. These spatially widespread changes accompanying long-term synaptic potentiation also reduced the neuron's ability to elicit spikes evoked through a nonpotentiated synaptic pathway. Our results suggest that the frequency response of these neurons depends on the dendritic location of their inputs and that activity can regulate their response dynamics within an oscillating neural network. Summary | Full Text | PDF (2604 kb)

• Contribution of electrogenic ion transport to impedance of t...

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Abstract

Excitation of Nitella internodal cell was investigated as an example of the phase transition in an open system far more thermal equilibrium. The power density spectrum of the membrane potential fluctuation had a bulge in a frequency range lower than 1 Hz at the resting state and a peak at approximately 0.03 Hz at a depolarized state near the threshold. A critical oscillation in the membrane potential was observed when threshold was gradually approached from the resting state. Repetitive firing was observed under a step-current of the superthreshold value. The frequency of spectral peaking, critical oscillation, and repetitive firing agree well with each other. The result suggests that the hard-mode instability occurs in the Nitella internodal cell. The membrane impedance had no peak in the same frequency region as the peak of the voltage spectrum. The spectral peak may be ascribed to be electrogenic pump modulated by the metabolic feedback system in photosynthesis.