A study by USC scientists of the brain connections in a small area of the rat brain showed them as patterns of circular loops, suggesting that at least in this part of the rat brain, the wiring diagram looks like a distributed network, rather than a hierarchy, the traditional view.

“We started in one place and looked at the connections. It led into a very complicated series of loops and circuits. It’s not an organizational chart. There’s no top and bottom to it,” said Larry W. Swanson, a member of the National Academy of Sciences and a professor of biological sciences at USC College. The study was published in Proceedings of the National Academy of Sciences August 9, 2010.

The circuit tracing method allows the study of incoming and outgoing signals from any two brain centers. It was invented and refined by USC neuroscientist Richard H. Thompson over eight years. Thompson is a research assistant professor of biological sciences at the College. Most other tracing studies at present focus only on one signal, in one direction, at one location.

“[We] can look at up to four links in a circuit, in the same animal at the same time. That was our technical innovation,” Swanson said.

The Internet model would explain the brain’s ability to overcome much local damage, he said. “You can knock out almost any single part of the Internet and the rest of it works.”Likewise, Swanson said, “There are usually alternate pathways through the nervous system. It’s very hard to say that any one part is absolutely essential.”

Swanson first argued for the distributed model of the brain in his book Brain Architecture: Understanding the Basic Plan (Oxford University Press, 2003). The PNAS study appears to support his view.

“There is an alternate model. It’s not proven, but let’s rethink the traditional way of regarding how the brain works,” he said. “The part of the brain you think with, the cortex, is very important, but it’s certainly not the only part of the nervous system that determines our behavior.”

The research described in the PNAS study was supported by the National Institute of Neurological Disorders and Stroke in the National Institutes of Health.

More info: USC news