Fig. 30.

Precision optogenetic modulation of neuronal circuits and behavior. (a) All-optical precision circuit interrogation is enabled by combining 2P imaging and cell-targeted holographic stimulation of a distributed pattern of multiple neurons, typically using a dedicated low-repetition rate (amplified) femtosecond laser. The illumination is extended across each neuron’s membrane by either rapid scanning, reducing the effective numerical aperture (at the cost of optical sectioning) or by parallel illumination of temporally focused extended shapes in two or three dimensions. (b) An array of methods are being developed to calibrate the projected light patterns, adjust as needed, and “smooth” their intensity profile (by minimizing holographic speckle⁵⁴⁷), and in some cases, validate and correct their precise targeting in situ inside the tissue.⁵⁴⁸ (c) Beyond target validation, all-optical precision neurophotonic interfaces enable direct readout of the effects of circuit perturbations with simultaneous imaging of neuronal activity (left panel from Ref. 536). This paradigm can be used to infer circuit connectivity and dynamics. One can also infer neuronal activity indirectly through animal behavioral reports of its (perturbed) perceptual experience (right panel, from Ref. 538), which informs us about the behavioral relevance of specific neurons and coding features.