Ghostbursting: a novel neuronal burst mechanism

Area of Science:

• Computational Neuroscience
• Electrophysiology
• Neurobiology

Background:

• Pyramidal cells in the electrosensory lateral line lobe (ELL) exhibit high-frequency burst discharge under constant depolarizing current.
• Previous models have not fully captured the complex bursting dynamics observed in these neurons.

Purpose of the Study:

• To develop a two-compartment model of an ELL pyramidal cell that replicates experimental burst discharges.
• To elucidate the underlying mechanisms of burst initiation, termination, and the transition to chaotic firing.

Main Methods:

• Constructed a two-compartment biophysical model of an ELL pyramidal cell.
• Applied quasi-static bifurcation theory to analyze burst termination dynamics.
• Investigated saddle-node bifurcations of limit cycles for tonic to bursting transitions.
• Performed experimental analysis of ELL pyramidal cell burst trains to validate model predictions.

Main Results:

• The model successfully reproduces burst discharges through a somatic-dendritic interaction mechanism.
• Burst termination is explained by phase space trajectory reinjection near a saddle-node bifurcation ghost, involving period doubling.
• Increased depolarization leads to resting, tonic firing, and chaotic bursting, with transitions governed by saddle-node bifurcations of limit cycles.
• Type I intermittency is identified as the route to chaos, supported by experimental data.

Conclusions:

• The developed model provides a mechanistic explanation for burst discharge in ELL pyramidal cells.
• The study highlights the role of saddle-node bifurcations and phase space dynamics in neuronal firing patterns.
• The findings offer insights into the generation of complex firing behaviors, including chaos, in biological neurons.