Local changes in potassium ions regulate input integration in active dendrites

by Malthe S. Nordentoft, Naoya Takahashi, Mathias S. Heltberg, Mogens H. Jensen, Rune N. Rasmussen, Athanasia Papoutsi

During neuronal activity, the extracellular concentration of potassium ions ([K⁺]_o) increases substantially above resting levels, yet it remains unclear what role these [K⁺]_o changes play in the dendritic integration of synaptic inputs. We here used mathematical formulations and biophysical modeling to explore the role of synaptic activity-dependent K⁺ changes in dendritic segments of a visual cortex pyramidal neuron, receiving inputs tuned to stimulus orientation. We found that the spatial arrangement of inputs dictates the magnitude of [K⁺]_o changes in the dendrites: Dendritic segments receiving similarly tuned inputs can attain substantially higher [K⁺]_o increases than segments receiving diversely tuned inputs. These [K⁺]_o elevations in turn increase dendritic excitability, leading to more robust and prolonged dendritic spikes. Ultimately, these local effects amplify the gain of neuronal input–output transformations, causing higher orientation-tuned somatic firing rates without compromising orientation selectivity. Our results suggest that local, activity-dependent [K⁺]_o changes in dendrites may act as a “volume knob” that determines the impact of synaptic inputs on feature-tuned neuronal firing.