Effects of extracellular potassium diffusion on electrically coupled neuron networks

Area of Science:

• Neuroscience
• Computational Neuroscience
• Biophysics

Background:

• Extracellular potassium accumulation and diffusion are observed during neuronal epileptiform activity.
• Potassium lateral diffusion is hypothesized to be vital in nonsynaptic neuron networks.

Purpose of the Study:

• To investigate the influence of extracellular potassium dynamics on stimulus-induced activity in a hippocampal CA1 pyramidal neuron network.
• To explore the interplay between potassium diffusion and gap-junction coupling in modulating neuronal network oscillations.

Main Methods:

• Simulated a hippocampal CA1 pyramidal neuron network under zero-calcium conditions.
• Modeled regulation of interstitial potassium concentration via potassium currents, Na(+)-K(+) pumps, glial buffering, and ion diffusion.
• Analyzed the effects of varying gap-junction conductance and potassium diffusive coupling on network activity.

Main Results:

• Stimulus-induced spike latency decreased with increasing gap-junction conductance, independent of potassium diffusion.
• Network oscillation duration exhibited a bell-shaped response to increasing potassium diffusion under weak gap-junction coupling.
• An optimal potassium diffusion strength was identified for modest electrical coupling, facilitating sustained action potential waves.

Conclusions:

• Gap-junction conductance significantly impacts spike latency, while potassium diffusion plays a more nuanced role in network oscillations.
• Extracellular potassium dynamics, particularly diffusion, are critical for modulating interstitial potassium concentrations and supporting network excitability.
• The findings highlight the importance of ion transport mechanisms in the generation and propagation of neuronal activity waves.