Imagine a map of every single star in an entire galaxy. A map so detailed that it lays out what each star looks like, what they’re made of, and how each star is connected to another through the grand physical laws of the cosmos.

While we don’t yet have such an astronomical map of the heavens, thanks to a momentous study published last week in Neuron, there is now one for the brain.

If every neuron were a galaxy, then synapses—small structures dotted along the serpentine extensions of neurons—are its stars. In a technical tour-de-force, a team from the University of Edinburgh in the UK constructed the first detailed map of every single synapse in the mouse brain.

Using genetically modified mice, the team literally made each synapse light up under fluorescent light throughout the brain like the starry night. And similar to the way stars differ, the team found that synapses vastly varied, but in striking patterns that may support memory and thinking.

“There are more synapses in a human brain than there are stars in the galaxy. The brain is the most complex object we know of and understanding its connections at this level is a major step forward in unravelling its mysteries,” said lead author Dr. Seth Grant at the Center for Clinical Brain Sciences.

The detailed maps revealed a fundamental law of brain activity. With the help of machine learning, the team categorized roughly one billion synapses across the brain into 37 sub-types. Here’s the kicker: when sets of neurons receive electrical information, such as trying to decide between different solutions for a problem, unique sub-types of synapses spread out among different neurons unanimously spark with activity…..more here