Per the team's study report (published in the April edition of the journal Proceedings of the National Academy of Sciences) a rat's brain is comprised of multiple layers. Two "local networks" (one controlling vision and learning, the other controlling muscle and organ function) make up the the inner layer, aka the cerebral cortex. Two other networks (one for smell, the other controlling the animal's cognitive functions), surround the cerebral cortex and make up the outer layer. According to the USC researchers, this means that certain sensory and information pathways are genetically hardwired to one another in ways that we've barely begun to explore. Additional analysis of the meta-study by Olaf Sporns of Indiana University found that these local networks interconnect at some 1,923 "regional hubs" (shown below), allowing information to flow freely between the neural regions.
The USC team chose to study rat brains given the sheer enormity of available data -- their meta-study database drew from 16,000 previous, peer-reviewed reports dating back to the 1970s and reportedly required more than 4,000 hours to compile. But this labor-intensive task could offer an incredibly valuable payoff. "Having a wiring diagram for the brain will allow knowledge to flow both ways between human and animal studies," Swanson said. "This allows us to take theories from human brain scan studies and experimentally verify them in animals, and discoveries made in animal studies are likely to have an analogue in humans."
[Illustration credit: PNAS]