Contents I. Introduction
When targeted with specific light-sensitive transmembrane proteins, e.g. microbial opsins, neurons of living animal models can be photosensitized, thus allowing light-induced modulation of their electrical activity. This combination of optics and genetics, known as optogenetics, has opened new frontiers for neuroscientists, in particular for studying neural microcircuits and their functional connectivity in awake and behaving animal models [1]–[2]. Indeed, with optogenetics it is possible to optically modulate electrical activity of molecularly defined classes of neurons, allowing the identification of their specific role in more complex circuits. The transmembrane proteins act as light-gated ion channels, responding to light by the generation of a flow of ions across the cellular membrane, which can depolarize or hyperpolarize the cell depending on the used protein [2]. For instance, Channelrhodopsin 2 (ChR2) - a non-specific cation channel-is widely used to generate action potentials, while halorodpsin and archaerhodopsin-light-driven ion pumps - are instead exploited to inhibit neural activity.
