It's now possible to imagine the whole brain of a fly in just a few days, according to a new study – this might sound like a long time, but it's actually a remarkable achievement, when you consider that the process will take weeks.
The brain is not easy to learn – the human brain, for example, contains more than 80 billion cells connected through each of 7,000 connections, according to new research published in Science. Even a much smaller fly brain is an amazing challenge to study comprehensively. This new study combines two microscope methods to image and examine the brain that has never existed before.
"This is a new tool for trying to understand biological networks, and not in the context of a single cell, but in a complete multi-cellular context at high resolution," Eric Betzig, Nobel physicist and recipient working at Janelia Research Campus at the Howard Hughes Medical Institute, told Gizmodo.
The researchers combined two types of microscopes, called expansion microscopes and light-lattice microscopes, to image the brain of a fly. Expansion microscopy involves first marking interesting features in the sample with fluorescent proteins, and then connecting them with polymer gel. The enzyme digests the tissue, and then the scientists add water, causing the polymer to grow and maintain a shape characterized by fluorescent proteins. In this case, they grow the sample four times.
But the expanded fly brain imaging will require around 20 trillion voxels, or 3d pixels, which will take weeks for electron microscopy for images. The team decided to combine expansion microscopes with other imaging methods, called light sheet microscopes. It uses thin, flat sheets of laser light and sample images in flat sections, allowing for a faster process that also reduces background noise.
Even Betzig didn't think the method would work at first, he told Gizmodo, but when he saw the results, he was "shocked" by the loyalty of expansion. Indeed, they are able to combine methods for making high-resolution images, up to tens of nanometers, according to the paper.
But this research is not at all capable of creating images of a similar human brain, explained Betzig. They expanded the method to (and have succeeded in imaging small pieces of) the brains of mice, but the brain of the fly versus the mouse brain was the same as "going from the mud hut to the Empire State Building," he said.
Researchers think they might soon be able to image many brains flying quickly and with extraordinary resolution. This is exciting, especially because the brain can vary for each person, and comparing many brains has the potential to teach us more about how this extraordinary biological achievement really works.