The ability to trigger neural activity with high resolution millimeters to centimeters deep in tissue remains an elusive goal in neuroscience research. Current research relies on using invasive electrodes, optogenetics, or pharmacological stimulation. None of these technologies, however, is capable of providing large-scale neural stimulation with high spatial resolution. In this project, we propose to combine piezoelectric barium titanate nanoparticles with ultrasound excitation to trigger neural activity. Ultrasound energy can be tightly focused in the brain with very high spatiotemporal resolution. However, ultrasound alone is not an efficient way to activate a specific set of neurons. Thus, we will use barium titanate nanoparticles to act as an embedded transducer to convert ultrasound to electrical energy. We will target the nanoparticles with antibodies to Neurofascin 186 receptors on rat hippocampal membranes, enabling neuron specific labeling at the axon initial segment. Then, highly focused ultrasound energy will be used to depolarize neurons with high spatial specificity. These methods will be validated with optical imaging of cultured rat hippocampal neurons labeled with Quasar, a genetically encoded fluorescent voltage sensor. Finally, we will investigate the mechanisms for action potential generation with the piezoelectric nanoparticles. These results will pave the way for in vivo ultrasound stimulation of groups of neurons at small spatial scales. Overall, the proposed technology has the potential to dramatically improve the ability to study complex neural networks.
Much is unknown about the interconnected networks in the brain and how they are related to disease. This is largely because the scientific community is lacking the tools needed for large-scale stimulation of neural activity. This application is focused on developing new tools that will enable new directions in neural disease research.