Functional optoacoustic neuro-tomography for scalable whole-brain monitoring of calcium indicators

Non-invasive observation of spatiotemporal activity of large neural populations distributed over entire brains is a longstanding goal of neuroscience. We developed a volumetric multispectral optoacoustic tomography platform for imaging neural activation deep in scattering brains. It can record 100 volumetric frames per second across scalable fields of view ranging between 50 and 1000 mm 3 with respective spatial resolution of 35–200 μm. Experiments performed in immobilized and freely swimming larvae and in adult zebrafish brains expressing the genetically encoded calcium indicator GCaMP5G demonstrate, for the first time, the fundamental ability to directly track neural dynamics using optoacoustics while overcoming the longstanding penetration barrier of optical imaging in scattering brains. The newly developed platform thus offers unprecedented capabilities for functional whole-brain observations of fast calcium dynamics; in combination with optoacoustics' well-established capacity for resolving vascular hemodynamics, it could open new vistas in the study of neural activity and neurovascular coupling in health and disease. Optoacoustics: brain imaging Scientists from Germany and Israel have developed an optoacoustic tomography method that can directly image fast neural activity in whole scattering brains. The team led by Daniel Razansky at the Helmholtz Center and Technical University in Munich and Shy Shoham from the Technion - Israel Institute of Technology discovered that genetically encoded calcium indicators have an optoacoustic signature and devised a rapid functional optoacoustic neuro-tomography system that can simultaneously record neural activity across volumes of 50 to 1000 cubic mm at 10 msec temporal resolution. The breakthrough technique was used to image the indicator GCaMP5G across adult zebrafish brains, thus overcoming the longstanding problem of light scattering that hindered penetration depth of fluorescence microscopy. The team says the technique could be readily customized to work with additional probes operating at longer wavelengths.