Mapping Synaptic Activity at the Population and Cellular Levels with Genetically Encoded Voltage Indicators (GEVIs).

In this chapter, we provide examples of using genetically encoded voltage indicators (GEVIs) to monitor neuronal intercellular communications at the population level (hippocampus of CA1 region) and individual cell level (retinal ganglion cells). Providing an optical readout for voltage transients, GEVIs enable the reporting of synaptic activity, both activation and inhibition, from chemical and electrical synapses. With the added flexibility of restricting expression of the GEVI to distinct cell types, GEVIs are becoming a powerful tool for interrogating neuronal activity.