Optical reporters of synaptic activity in neural circuits

One of the most basic computational elements within a circuit is the synapse across which signals are transferred. Here we summarize some experimental strategies that allow the synaptic basis of circuit function to be studied through imaging. The two most promising approaches available currently are pHluorin-based reporters of synaptic vesicle fusion and genetically encoded calcium indicators localized to presynaptic terminals. Other potential approaches include the optical sensing of local voltage changes or of neurotransmitter substances, but the spatial and temporal sensitivity of the current reporters would need to be improved.