Gating information by two-state membrane potential fluctuations.
Two-state voltage fluctuations between a hyperpolarized down-state and a depolarized up-state have been observed experimentally in a wide variety of neurons across brain regions. Using a biophysical model, we show that synaptic input by NMDA receptors can cause such membrane potential fluctuations. In this model, when a neuron is driven by two input pathways with different AMPA/NMDA receptor content, the NMDA-rich input causes up-state transitions, whereas the AMPA-rich input generates spikes only in the up-state. Therefore the NMDA-rich pathway can gate input from an AMPA pathway in an all-or-none fashion by switching between different membrane potential states. Furthermore, once in the up-state, the NMDA-rich pathway multiplicatively increases the gain of a neuron responding to AMPA-rich input. This proposed mechanism for two-state fluctuations directly suggests specific computations, such as gating and gain modulation based on the distinct receptor composition of different neuronal pathways. The dynamic gating of input by up- and down-states may be an elementary operation for the selective routing of signals in neural circuits, which may explain the ubiquity of two-state fluctuations across brain regions.
Kepecs
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A
Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA. kepecs@cshl.edu
Raghavachari
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S
D000465:Algorithms; D001921:Brain / Q000166:cytology / Q000502:physiology*; D003712:Dendrites / Q000502:physiology; D004594:Electrophysiology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology*; D008959:Models, Neurological; D009415:Nerve Net / Q000166:cytology / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D016012:Poisson Distribution; D018091:Receptors, AMPA / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology*
D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate