Sensorless adaptive optics implementation in widefield optical sectioning microscopy inside in vivo Drosophila brain

Adaptive optics light-sheet microscopy based on direct wavefront sensing without any guide star

We propose an adaptive optics light-sheet fluorescence microscope (AO-LSFM) for closed-loop aberrations' correction at the emission path, providing intrinsic instrumental simplicity and high accuracy when compared to previously reported schemes. The approach is based on direct wavefront sensing, i.e., not on time-consuming iterative algorithms, and does not require the use of any guide star, thus reducing instrumental complexity and/or sample preparation constraints. The design is based on a modified Shack-Hartmann wavefront sensor providing compatibility with extended sources such as images from optical sectioning microscopes. We report an AO-LSFM setup based on such sensors, including characterization of the sensor performance, and demonstrate for the first time to the best of our knowledge a significant contrast improvement on neuronal structures of the ex vivo adult drosophila brain in depth.

Optical properties of adult Drosophila brains in one-, two-, and three-photon microscopy

Drosophila is widely used in connectome studies due to its small brain size, sophisticated genetic tools, and the most complete single-neuron-based anatomical brain map. Surprisingly, even the brain thickness is only 200-μm, common Ti:sapphire-based two-photon excitation cannot penetrate, possibly due to light aberration/scattering of trachea. Here we quantitatively characterized scattering and light distortion of trachea-filled tissues, and found that trachea-induced light distortion dominates at long wavelength by comparing one-photon (488-nm), two-photon (920-nm), and three-photon (1300-nm) excitations. Whole-Drosophila-brain imaging is achieved by reducing tracheal light aberration/scattering via brain-degassing or long-wavelength excitation at 1300-nm. Our work paves the way toward constructing whole-brain connectome in a living Drosophila.

High speed wavefront sensorless aberration correction in digital micromirror based confocal microscopy

The quality of fluorescence microscopy images is often impaired by the presence of sample induced optical aberrations. Adaptive optical elements such as deformable mirrors or spatial light modulators can be used to correct aberrations. However, previously reported techniques either require special sample preparation, or time consuming optimization procedures for the correction of static aberrations. This paper reports a technique for optical sectioning fluorescence microscopy capable of correcting dynamic aberrations in any fluorescent sample during the acquisition. This is achieved by implementing adaptive optics in a non conventional confocal microscopy setup, with multiple programmable confocal apertures, in which out of focus light can be separately detected, and used to optimize the correction performance with a sampling frequency an order of magnitude faster than the imaging rate of the system. The paper reports results comparing the correction performances to traditional image optimization algorithms, and demonstrates how the system can compensate for dynamic changes in the aberrations, such as those introduced during a focal stack acquisition though a thick sample.