Recently, the journal Science showed in its cover an amazing image of a close up into the fly brain. This is the result of the combined effort of two research groups working on imaging. The first one (Boyden’s) had developed a way to increase the size of preserved samples, like a brain slice, up to 4 times by using an absorbable polymer similar to the one used in baby diapers and dosing it with water while at the same time making them transparent. The second technique, lattice light-sheet microscope from the Betzig lab 1, is based on an ultrathin sheet of light which illuminates only the part in the microscope’s plane of focus. That helps out-of-focus areas stay dark, keeping a specimen’s fluorescence from being extinguished. This characteristic, together with its speed, made it a plausible ideal choice for the microscope to image huge chunks of expanded brains, and so it was. Even though the samples had to be repositioned and the image data acquired repositioned and stitched so as to rebuild the whole 3D data set (with the huge amount of data that implies), the whole acquisition time
was relatively short: 62 hours.
They traced proteins, tiny cellular protrusions known as dendritic spines, and dopaminergic neurons. And that is just an example of the range of possibly interesting things to investigate with such a technique. Depending on labelling, in the future, it would be possible to track neuron connections, examine neurotransmitter or neuron type distribution…
Mapping ignorance
