By looking at 40 years worth of brain research, scientists at the University of Southern California have created a very robust map of a rat brain.
They discovered the minds of rodents are organized in patterns similar to those used by the airline industry, with a dense network of regional connections and a few longer connection uniting distant areas.
This new way of thinking of rat brains could help scientists do a better job of mapping and understanding the human brain as well, said Larry Swanson, professor at the USC's Dornsife College of Letters, Arts and Sciences.
“What we’re trying to do is basically figure out... what’s the basic pattern of the brain’s wiring diagram?” said Swanson who co-authored a paper on this research.
(An image showing the major connections uniting the parts of the cerebral cortex in a rat brain. Image from the article "Architecture of the cerebral cortical association connectome underlying cognition" by Bota et al. published in PNAS 2015 10.1073/pnas.1504394112.)
He and co-author Mihail Bota, also with USC, collected more than 16,000 scientific reports on rodent brain connectivity and complied the findings into a massive online database.
Through detailed analysis of the various connections, they determined that the cerebral cortex of rats are broken into four distinct regions filled with lots of dense connections.
Swanson likened these to continents filled with many regional flights.
However, there are also some connections uniting the four regions. Swanson says these are like international flights that connect various continents.
Each of the four regions has a very different role, he noted.
One seems to process stimuli from the outside world by taking information from sensory organs like the eyes and ears.
Another controls the body, muscles and internal organs. The third region seems to involve smell and memory.
The fourth appears to integrate all of the other modules, Swanson explained, making it perhaps the highest level of cognitive functioning for a mouse.
(This graphic shows the four main regions of cerebral processing identified in rat brains. Image from the article "Architecture of the cerebral cortical association connectome underlying cognition" by Bota et al. published in PNAS 2015 10.1073/pnas.1504394112.)
While mice and men are quite different creatures, many studies have shown there are some overarching physical similarities in the two species, from the digestive system to the basic design of skeletons and muscles.
“Rats and mice are mammals, just like people are," he said. "There are some commonalities between all mammals.”
That's why so many treatments designed for humans are often tested first on rodents.
Similarly, Swanson says his new findings on rodent brains might help give a paradigm for brain researchers to use when trying to understand human cerebral cortices.
The goal is to one day have a comprehensive enough map of neural connections in a healthy human brain so that researchers can compare that to brains dealing with things like autism, schizophrenia and learning disorders.
“We’re thinking in the long run we could actually use the pattern of connections... to actually classify mental health problems,” Swanson said.
The research was published April 6th in the journal Proceedings of the National Academy of Sciences.