Photonic technologies for optogenetics

Light-induced stimulation and inhibition of neuronal activity has been recently made possible by optogenetics. In optogenetics, specific light-sensitive proteins, called opsins, are genetically targeted into specific neuronal cell types in an animal model. When light of the appropriate wavelength is delivered into the brain, the light-activated proteins respond by stimulating or inhibiting the firing of action potentials in neurons. It is therefore possible to switch on and off different types of neurons merely by turning on a light. Delivering of light in vivo to specific neurons at specific locations in the brain is still a challenge, however. Here we review recent advances on micro and nanotechnologies for the fabrication of optogenetic devices to deliver light in vivo at specific, controlled sites in mammalian brains, while simultaneously monitoring their electrical activity.