Light-Based Neuronal Circuit Probing in Living Brains at High Resolution: Constraints and Layouts for Integrating Neuronal Activity Recording and Modulation in Three Dimensions

Understanding how the brain orchestrates neuronal activity to finely produce and regulate behavior is an intriguing yet challenging task. In the last years, the progressive refinement of optical techniques and light-based molecular tools allowed to start addressing open questions in cellular and systems neuroscience with unprecedented resolution and specificity. Currently, all-optical experimental protocols for simultaneous recording of the activity of large cell populations with the concurrent modulation of the firing rate at cellular resolution represent an invaluable tool. In this scenario, it is becoming everyday more evident the importance of sampling and probing the circuit mechanisms not just in a single plane, but extending the exploration to the entire volume containing the involved circuit components. Here, we focus on the design principles and the hardware architectures of all-optical approaches allowing for studying the neuronal dynamics at cellular resolution across a volume of the brain.