Toward Circuit Optogenetics

Parallel holographic illumination has emerged as a technique of choice for two-photon optogenetic control of neuronal circuits organized in three dimensions. Complementary variants of 3D holographic illumination are optimized for simplicity, temporal precision, or axial resolution. The possibility of reaching hundreds of targets in 3D volumes has prompted the development of low-repetition-rate amplified laser sources that achieve high total exit power while keeping low the average power exposure of each cell. These advances allow neuronal circuits distributed between different brain areas to be optically interrogated and controlled with millisecond temporal precision and single-cell resolution. I will review past accomplishments and necessary future developments in circuit optogenetics.