A technology that could provide a path towards the holy grail of systems neuroscience - gain a level of understanding about the dynamics of neural circuits - is proposed. The technology is based on nano photonics - optical elements that are nanometer in size and can be massively integrated into small chips that could then be inserted into the animal brain. This platform would enable light to be delivered to thousands of different locations in the brain and would enable stimulation of neurons with arbitrary dynamical patterns. This proposed approach is expected to provide a critical stepping stone towards one of the greatest challenges facing science today - the understanding how the brain works. It will not only enable a new class of experiments to advance basic biological knowledge but could eventually contribute to an understanding of neurological and neuropsychiatric diseases.
Optical stimulation and silencing of neural activity is a powerful technique for elucidating the structure and function of neural circuitry, however in most in vivo optogenetic experiments, light is delivered into the brain through a single optical fiber limiting illumination to a large, fixed volume of the brain. A novel nanophotonic platform is proposed to allow massively parallel, multi-site stimulation through a single waveguide. Recent advances in nanophotonics enable the proposed optical probe platform which routes input light to an arbitrary excitation spot. The proposed platform is designed to be compatible with standard silicon probes for electrophysiological recordings. The proposed platform is based on nanowaveguides that consist of Silicon Nitride (SiN) wires with ~0.5 micrometers in diameter embedded in SiO2, that just like fibers, are transparent to light of wavelengths from the UV down to the mid-IR, and can be centimeters long. When compared to fibers, however, they are much smaller and enable light to be emitted from the nano-waveguides forming multiple beams at arbitrary locations. A first-generation probe will be fabricated, tested and then integrated with a state of art electrical probe for neural validation. This integrated device will then be used in mouse cortex to demonstrate the ability of waveguides to provide sufficient light for ChR2 activation and selective activation across cortical layers.
