Subthreshold membrane potential oscillations
Neurons produce action potentials when their membrane potential increases past a critical threshold. If the voltage is below the threshold the neuron does not fire, but the membrane potential still fluctuates due to postsynaptic potentials and intrinsic electrical properties of neurons. In some type of neurons, the membrane potential can oscillate at specific frequencies. Although subthreshold oscillations do not directly result in neuronal firing, they may facilitate synchronous activity of neighboring neurons. It may also facilitate computation, particularly processing of sensory signals
Neurons display, beyond synaptic and action potentials, rhythmic subthreshold membrane potential oscillations (a particular type of neural oscillations). These oscillations, which resembled sinusoidal wave forms were originally discovered in the mammalian inferior olive nucleus cells. The functional relevance of subthreshold oscillations concerns the nature of the intrinsic electrical properties of neurons, that is, the electrical responsiveness not derived from interactions with other cells. These properties define the dynamic phenotype independently from form or connectivity. Subthreshold oscillation frequency can vary, from few Hz to over 40 Hz and their dynamic properties have been studied in detail in relation to neuronal activity coherence and timing in CNS, in particular with respect to the 10 Hz physiological tremor that controls motor execution, Theta rhythm in the entorhinal cortex and gamma band activity in cortical inhibitory interneurons and in thalamus neurons. They have also been described and studied in layers V of the entorhinal cortex, the inferior olive in vivo, the olfactory bulb and the dorsal cochlear nucleus. The dynamic aspects of such oscillations have been defined using mathematical modeling.
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