Neural stimulation is a standard tool in neuroscience, allowing researchers to specifically study the role individual or groups of neurons play in a larger interconnected circuit. Despite its widespread applicability, however, there remains no reliable method to noninvasively stimulate a specific set of neurons. Current approaches rely on implanted electrodes, genetic modification, and/or invasive optical fibers. These not only restrict the long-term applicability of these technologies, but also may influence the measurements themselves. Thus, a reliable method for noninvasive neural stimulation could advance the field of neuroscience and enable new therapeutic approaches for conditions where neural stimulation has shown promise. We have developed a method where ultrasound energy is used to excite piezoelectric nanoparticles. Upon exposure to the energy, the piezoelectric nanoparticles build up an electric charge on their surface. We hypothesize that this enables them to trigger voltage sensitive ion channels in the neurons. Our in vitro data indicate that ultrasound stimulation of calcium and glutamate activity only reliably occurs when piezoelectric nanoparticles are present. In this proposal, we seek to take the first steps to applying the technology in vivo. The overall goal of this project is to establish that the piezoelectric nanoparticles can be used to enable ultrasound stimulation of neurons in brain slices and in vivo. We will first identify ideal ultrasound stimulation parameters and nanoparticle concentrations by using brain slice preparations. Then we will apply these ideal parameters to living rats. We will stimulate the motor cortex and use a combination of local field potentials and electromyography to measure the resulting neural stimulation. Overall, this study will result in demonstrating that piezoelectric nanoparticles can be harnessed for reliable ultrasonic neurostimulation in vivo.
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 noninvasive stimulation of neural activity. This application is focused on developing new tools that will enable new directions in neural disease research.