Imaging membrane potential in dendrites and axons of single neurons.

This review focuses on the use of imaging techniques to record electrical signaling in the fine processes of neurons such as dendrites and axons. Voltage imaging began with the use and development of externally applied voltage-sensitive dyes. With the introduction of internally applied dyes and advances in detection technology, it is now possible to record supra-threshold action potential responses, as well as sub-threshold synaptic potentials, in fine neuronal processes including dendritic spines. The development of genetically coded sensors, as well as variants of laser scanning microscopy such as second harmonic generation, offers promise for further advances in this field. Through the use and further development of these methods, optical imaging of membrane potential will continue to be a valuable tool for investigators wishing to explore the electrical events underlying single neuronal computation.