Neuroscientists have begun testing the most powerful brain imaging technology ever created, and it's already helped them answers questions about how connections form in our most complex organ.
The new imaging tool allows researchers to probe into every nook and cranny of the brain and then use the data to produce images at the nanoscale, like the one in the video above.
A large collective of researchers at Harvard, John Hopkins, and other institutions tested out the new technology by inspecting a mouse's neocortex, according to a paper published Thursday in Cell. With such detailed imaging, every cellular object in the mouse's neocortex (that would be the axons, dendrites, and glia, if you haven't had a biology refresher in a while) were distinguishable and most of the sub-cellular components, such as synapses and spines, were visible as well.
"The complexity of the brain is much more than what we had ever imagined," said lead author Narayanan "Bobby" Kasthuri, of the Boston University School of Medicine, in a press release. "We had this clean idea of how there's a really nice order to how neurons connect with each other, but if you actually look at the material it's not like that. The connections are so messy that it's hard to imagine a plan to it, but we checked and there's clearly a pattern that cannot be explained by randomness."
In the paper, the researchers explain how they were already able to make some significant discoveries just by poking around the mouse's brain. In the process, they were able to refute a long-held belief that the if you knew exactly where axons and dendrites were in a part of the brain, you could predict the connectivity between them (this is called Peters' rule). According to their research, that's not always the case. Because the new technology enabled neuroscientists to trace the connections in a mouse's brain with greater precision, they discovered there's something more complex going on.
"Axon-dendrite adjacency, while of course necessary for synapses to form, is insufficient to explain why some axons establish multiple synapses on some dendrites and not others," the paper reads. "This is an explicit refutation of Peters' rule. Rather this result argues that there are different probabilities for synapses between particular dendrites and particular excitatory axons."
While understanding how synapses form in a mouse brain might not thrill you, the fact that the researchers were able to form this new understanding through advanced imaging should. As the technology becomes more affordable and available, it could be used to help us finally explore the many mysteries of the human brain, from neural disorders to psychopathy.
"As long as data is showing you things that are unexpected, then you're definitely doing the right thing," said Jeff Lichtman, a Harvard neurobiologist and senior author of the study, in the release. "And we are certainly far from being out of the surprise element. There's never a time when we look at this data that we don't see something that we've never seen before."