During neural activity, the extracellular concentration of potassium ions, [K+]o, increases substantially above resting levels. However, the role that these dynamic [K+]o changes play in the integration of synaptic inputs in the dendrites remains enigmatic. In this study, Nordentoft et al. use mathematical formulations and biophysical modeling to propose the novel concept that local, activity-dependent changes in [K+]o create dendritic “[K+]o hotspots”. The authors further find that the spatial arrangement of inputs dictates the magnitude of the [K+]o changes near the dendrites; dendritic segments receiving similarly-tuned inputs (also known as functional synaptic clusters) can attain substantially higher [K+]o increases than segments receiving diversely-tuned inputs, giving rise to the “[K+]o hotspots”. These [K+]o elevations in turn transiently and selectively increase dendritic excitability, leading to more robust and prolonged dendritic spikes. Notably, these local effects amplify the gain of neuronal input-output transformations, causing higher sensory feature-tuned somatic firing rates without compromising feature selectivity. Collectively, these 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.

Image Credit: Antonis Asiminas