Mapping homeostatic synaptic plasticity using cable properties of dendrites

• We derive a new electrophysiological parameter, the dendritic filtering index (DFI).
• The DFI describes the shape of AMPA receptor currents.
• The DFI allows mapping of the dendritic origin of synaptic currents.
• The DFI reveals distinct forms of homeostatic plasticity in different neuron types.

When chronically silenced, cortical and hippocampal neurons homeostatically upregulate excitatory synaptic function. However, the subcellular position of such changes on the dendritic tree is not clear. We exploited the cable-filtering properties of dendrites to derive a parameter, the dendritic filtering index (DFI), to map the spatial distribution of synaptic currents. Our analysis indicates that young rat cortical neurons globally scale AMPA receptor-mediated currents, while mature hippocampal neurons do not, revealing distinct homeostatic strategies between brain regions and developmental stages. The DFI presents a useful tool for mapping the dendritic origin of synaptic currents and the location of synaptic plasticity changes.