359 — Cortical Column and Whole Brain Imaging of Neural Circuits with Molecular Contrast and Nanoscale Resolution

Conventionally, researchers have had to choose between high resolution and high speed: You can either image everything and get molecular resolution, or you can image large volumes of tissue. Attempting to do both results in either too slow of a process, or far too much data to reasonably manage.

Expansion microscopy is a technology that physically increases the size of a sample in order to make it visible in lower-spatial-acuity modalities. Using lattice light sheet microscopy (LLSM) in combination with expansion microscopy (ExM), the authors propose ExLLSM, which renders even miniscule spine heads at high enough resolution at 4× to capture in light microscopy.

Because this requires the stitching together of many thousands of volumes of 3D data into the final render, the researchers also developed an Apache Spark-based stitching process for tera-scale image recombination.

The authors use this technology to explore subcellular structures, spine distribution, and myelination in mouse cortex, as well as neuron Drosophila stereotypy in clustered projecting neurons in the olfactory mushroom body.

Hugely important to the use-case of this technology is that it, unlike electron microscopy, enables the visualization of fluorescent markets in the tissue. This technology has also been used on the mossy fiber innervations of mouse cerebellum, improving our ability to understand these complex synapse structures. Though higher expansion coefficients than 4 are possible, the artifacts of this expansion process become less predictable with scale.