  Non-invasive observation of spatiotemporal neural activity of large neural
populations distributed over entire brains is a longstanding goal of
neuroscience. We developed a real-time volumetric and multispectral
optoacoustic tomography platform for imaging of neural activation deep in
scattering brains. The system can record 100 volumetric frames per second
across a 200mm3 field of view and spatial resolutions below 70um. Experiments
performed in immobilized and freely swimming larvae and in adult zebrafish
brains demonstrate, for the first time, the fundamental ability to
optoacoustically track neural calcium dynamics in animals labeled with
genetically encoded calcium indicator GCaMP5G, while overcoming the
longstanding penetration barrier of optical imaging in scattering brains. The
newly developed platform offers unprecedented capabilities for functional
whole-brain observations of fast calcium dynamics; in combination with
optoacoustics' well-established capacity in resolving vascular hemodynamics, it
could open new vistas in the study of neural activity and neurovascular
coupling in health and disease.
