Buckner and Krienen call their idea the tether hypothesis and present it in a paper in the December issue of the journal Trends in Cognitive Sciences.
“I think it presents some pretty exciting ideas,” said Chet Sherwood, an expert on human-brain evolution at George Washington University who was not involved in the research.
Buckner and Krienen developed their hypothesis after making detailed maps of the connections in the human brain using fMRI scanners. When they compared their maps with those of other species’ brains, they saw striking differences.
The outer layers of mammal brains are divided into regions called cortices. The visual cortex, for example, occupies the rear of the brain. That is where neurons process signals from the eyes, recognizing edges, shading and other features.
There are cortices for the other senses, too. The sensory cortices relay signals to another set of regions called motor cortices. The motor cortices send out commands. This circuit is good for controlling basic mammal behavior.
“You experience something in the world, and you respond to it,” Krienen said.