High-Speed All-Optical Neural Interfaces with 3D Temporally Focused Holography

Excerpt

Understanding brain function requires technologies that can monitor and manipulate neural activity with cellular resolution and millisecond precision in three dimensions across large volumes. These technologies are best designed using interdisciplinary approaches combining optical techniques with reporters and modulators of neural activity. While advances can be made by separately improving optical resolution or opsin effectiveness, optimizing both systems together matches the strengths and constraints of different approaches to create a solution optimized for the needs of neuroscientists. To achieve this goal, we first developed a new multiphoton photoexcitation method, termed 3D-Scanless Holographic Optogenetics with Temporal focusing (3D-SHOT), that enables simultaneous photoactivation of arbitrary sets of neurons in 3D. Our technique uses point-cloud holography to place multiple copies of a temporally focused disc, matched to the dimensions of a neuron’s cell body, anywhere within the operating volume of the microscope. However, since improved placement of light, on its own, is not sufficient to allow precise control of neural firing patterns, we also developed and tested optogenetic actuators ST-ChroME and ST-eGtACR1 that fully leverage the new experimental capabilities of 3D-SHOT. The synergy of fast opsins matched with our technology allows reliable, precisely timed control of evoked action potentials and enables on-demand read-write operations with unprecedented precision. In this chapter, we review the steps necessary to implement 3D-SHOT and provide a guide to selecting ideal opsins that will work with it. Such collaborative, interdisciplinary approaches will be essential to develop the experimental capabilities needed to gain causal insight into the fundamental principles of the neural code underlying perception and behavior.