Good shape photolysis

Investigation of signal transmission in brain requires to reproduce/observe physiological events that occur on a wide range of spatiotemporal scales. Light microscopy is a fundamental tool in neuroscience offering a sensitive non invasive approach of probing and mimicking such brain complexity. This paper demonstrates that an effective way of covering a broad range of signaling patterns is to control light excitation by the engineering of optical wave-fronts obtained by phase modulation solely. Based on this approach a novel microscope configuration that incorporates a nematic liquid crystal spatial light modulator to generate single photon holographic patterns is presented and it is shown that, for large illumination area, holographic illumination enables to achieve a significantly improved axial resolution relative to Gaussian illumination. This microscope can produce illumination spots of variable size and number and patterns shaped to precisely match user-defined elements in a specimen. Combining holographic photo-activation with electrophysiology recording, glutamate uncaging in brain slices is performed and it is demonstrated that a precise engineering of optical wave- fronts, allows for a precise spatiotemporal shaping of neuronal currents.