Imagine a map with each star in the galaxy. The map is so detailed that it shows what each star looks like, what it consists of, with what other star is bound by the great laws of the physics of the cosmos. Although we do not yet have such an astronomical map of the heavens, thanks to a monumental study published last week in Neuron, we had a similar brain map.
If each neuron was a galaxy, the synapses are small structures dotted along serpentine neuron continuations – these are the stars. A team of scientists from the University of Edinburgh in the UK built the first detailed map of each synapse in the brain of the mouse.
Brain map: the key to the puzzle of thinking
Using genetically modified mice, scientists literally made every synapse illuminate under the fluorescent light throughout the brain, like the stars in the sky. And, just as the stars differ from each other, scientists have discovered that synapses are also very diverse, but regularities that can support the work of memory and thinking are observed.
“There are more synapses in the human brain than stars in the galaxy. The brain is the most complex object known to us and understanding its connections at this level will be an important step forward in uncovering its mysteries, “says lead author Dr. Seth Grant of the Center for Clinical Brain Sciences.
Detailed maps showed the fundamental law of brain activity . With the help of machine learning, a team of scientists divided roughly one billion synapses throughout the brain into 37 categories by type. That's the point: when the sets of neurons receive electrical information, for example, when choosing between different solutions to the problem, the unique subtypes of synapses scattered among different neurons are unanimously sparked by activity. In other words, synapses come in different types. And every type can control thought, decision or memory.
It's no surprise that neuroscientists reacted positively to the work.
“Wow,” commented Ben Sanders of the University of Minnesota.
This “amazing article cataloging diversity and distribution subtypes of the synapse across the mouse's brain, “writes neuroscientist Kevin Mitchell. This “emphasizes the fact that synapses are the key computational elements of the nervous system.”
The interest of scientists in creating the “synaptic” – the first whole catalog of synapses in the brain of the mouse – came from a much larger project: 19659005] Briefly, a connector is all the neural connections within you. As Dr. Sebastian Syung says, the connector is the biological basis of who you are – your memories, personality, your thoughts and reasonings. Catch the connection – and one day scientists will be able to restore you by emulating the whole brain.
And yet, the connector describes only how neurons functionally talk to each other. Where in the brain it is physically encoded.
Synapses come into play here. Neuroscientists have long known that synapses transmit information between neurons, using chemicals and electricity. There were also hints that the synapses vary greatly depending on the proteins that they contain, but this difference is usually ignored. Until recently, most scientists believed that real calculations occur in the neural bulb of the neuron from which the branches branch out.
Until now, there has been no way to look at the morphology and function of the synapses throughout the brain, the authors of the work explain. Usually, we focused on comparing these important junction points in small areas.
“A synaptic map can be used to understand whether the spatial distribution of synapses is related to the architecture of the connector,” scientists believe.
And if so, the future emulators of the brain will finally find a fulcrum.
In order to construct a mouse synaptic, the authors developed a plan called SYNMAP. They started with genetically modified mice, in which synapses glowed in different colors. Each synapse is densely manned by different proteins, among which the PSD-95 and SAP102 are the most famous gentlemen. Do not be afraid of names. The authors added luminous proteins to them, which acted as lanterns that illuminated every synapse in the brain.
In general, scientists first changed the biology of the mouse, causing its synapses to glow under fluorescent light.
Then they laboriously cut the brain into pieces, used a microscope to capture synapses in different areas of the brain and collected photos together.
The image of the synapses reminds the inexperienced eye of a tightly packed star chart – like the one that Hubble recently photographed. The categorization of each synapse goes beyond the abilities (and time) of any person, so scientists used new methods of classification with machine learning and developed an algorithm that parses this data – more than 10 terabytes – automatically without the need for supervision.
Physical Connectivity  At first, scientists were impressed by the “expressive schemes” of the shining synapses. One tagged protein, PSD-95, seemed to be hanging out in the more remote parts of the brain, where higher cognitive functions were taking place. Although the regions overlap, another luminous protein preferred more internal regions of the brain.
On closer examination, it was found that two luminous proteins represent different sets of synapses, the authors explained. Each area of the brain has a characteristic “signature of the synaptic”. Like fingerprints that differ in shape and size, different regions of the brain seem to contain synapses that differ in protein composition, size, and abundance.
Using a specially developed algorithm for machine learning, scientists classified synapses into 37 subtypes. Remarkably, brain regions associated with higher thinking and thinking abilities also contained the most diverse synapsial population, while “reptilian brain regions” were more homogeneous in the content of synapses.
To see if a variety of synapses helps in the processing of information, scientists have used computer simulations to show how synapses respond to conventional electrical circuits in the hippocampus, a region of the brain important for learning and memory. The hippocampus is one of the areas that demonstrate a striking variety in the synaptic subtypes.
What is important, each type of processing of electrical information is transferred to a unique synaptic map – change the input, the synaptic will change.
This suggests that the brain can process multiple electrical information using a single area of the brain, because different synapsomes are involved.
Scientists have found similar results when electric circuits of the brain of mice recording three variants of the award. Various synapses were ignited when the choice was right or wrong. Like a map of inner thinking, the synaptic drew a vivid picture of what the mouse was thinking, making choices.
Each behavior activates a separate synaptic. Each synaptic is a unique mold of the thought process.
Reprogramming the synaptic
Like the computer code, the synaptic seems to be at the heart of the computational result – decision or thought. What if I change this code?
Psychiatric diseases often have genetic causes that affect proteins in the synapse. Using mice that showed symptoms similar to schizophrenia or autism, the scientists charted their synaptic – and found dramatic changes in the way in which various subtypes of synapses are structured and connected in the brain.
For example, in response to conventional electrical circuits of the brain, some Synaptic maps showed poorly, while others became abnormally strong in mutant mice. Mutations can change the synaptic and potentially lead to psychiatric disorders. That is, some psychiatric diseases “reprogram” the synaptic. Stronger or simply new synaptic maps may be the reason that patients with schizophrenia experience delusions and hallucinations.
So you are your synaptic?
Perhaps. The essence of you – memories, thoughts – seems to be imprinted on how different synapses are activated in response to input. As if from a fingerprint, a synaptic could be read to decipher what you are thinking about. However, this research is only the beginning. Neuroscientists have yet to analyze the complex connections between synapses and you.
“This card opens up many new research areas that must transform our understanding of brain behavior and diseases,” Grant says.