Miniaturized optogenetic neural implants: a review

Optogenetics is an exciting new technology that allows targetable fast control and readout of specific neural populations in complex brain circuits. With the rapid development of light-sensitive microbial opsins, substantial gains in understanding the causal relationships between neural activity and behavior in both healthy and diseased brains have been achieved during the last decade. However, the intricate and complex interactions between different neural populations in mammalian brains require novel, implantable, neural interfaces that are capable of manipulating and probing targeted neurons at multiple sites and with high spatiotemporal resolution. Advanced microtechnology has offered the highest potential to meet these demands of optogenetic applications. In this paper, we review a variety of miniaturized optogenetic neural implants developed in recent years, based on different light sources, including lasers, laser diodes, and light-emitting diodes. We then summarize the specifications of these microimplants and their related microfabrication approaches and discuss the major challenges of current techniques and the vision for the future of the field. This article reviews recent developments in miniaturized neural implants for optogenetics, highlights major improvements enabled by microtechnologies, and discusses challenges faced by developers and adopters of these new technologies.