Abstract
Many neurons display bistability–coexistence of two firing modes such as bursting and tonic spiking or tonic spiking and silence. Bistability has been proposed to endow neurons with richer forms of information processing in general and to be involved in short-term memory in particular by allowing a brief signal to elicit long-lasting changes in firing. In this paper, we focus on bistability that allows for a choice between tonic spiking and depolarization block in a wide range of the depolarization levels. We consider the spike-producing currents in two neurons, models of which differ by the parameter values. Our dopaminergic neuron model displays bistability in a wide range of applied currents at the depolarization block. The Hodgkin-Huxley model of the squid giant axon shows no bistability. We varied parameter values for the model to analyze transitions between the two parameter sets. We show that bistability primarily characterizes the inactivation of the Na+ current. Our study suggests a connection between the amount of the Na+ window current and the length of the bistability range. For the dopaminergic neuron we hypothesize that bistability can be linked to a prolonged action of antipsychotic drugs.
Highlights
Bistability – coexistence of two firing modes in the same experimental conditions – has been documented in different types of neurons
In this study we focus on the bistability at the transition to the state called depolarization block – a silent state that occurs in every neuron when it receives excessive excitation
Our results show that the silent state of depolarization block may be stable together with the tonic spiking state
Summary
Bistability – coexistence of two firing modes in the same experimental conditions – has been documented in different types of neurons. Tonic spiking coexists with bursting [1] or with a different spiking mode [2] in leech heart cells. Bistability of bursting and spiking was discovered in neuron R15 of the marine mollusk Aplysia [3]. We focus on the bistability between a resting and tonic spiking states. This type of bistability was observed in different motor neurons [4,5,6]. A short signal triggers a long-lasting change in the firing, which encodes the last input. Bistability is common among neurons and endows them with richer forms of information processing
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