Local changes in potassium ions regulate input integration in active dendrites

AU During: Pleaseconfirmthatallheadinglevelsarerepresentedcorrectly 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.