One brain system where autistic people seem to have abnormal connections is the "default mode network."
This widely spaced brain network is a hot topic in neuroscience research. Sometimes called the "daydreaming" network, it seems to be most active when people are not carrying out any particular mental task, but are reflecting on their feelings, past behaviors and future actions.
When Stuart Washington of Georgetown University and his colleagues examined autistic people with functional magnetic resonance imaging, they found that certain parts of their default mode networks were "hyperconnected."
The unusual links showed up in two parts of a horseshoe-shaped area in the middle of the brain: the anterior and posterior cingulate. Previous tests have shown that these parts of the brain are involved in responding to rewards, detecting how important something is, and memory.
One possible result of this localized overconnection, the Georgetown researcher said, is that people with autism may "tend to hyperfocus on a particular task and then when the task ends they can't bring themselves to stop focusing on it."
At the same time, the researchers found that the entire default mode network was more weakly connected in people with autism. Since proper functioning of the network may be vital for people to have a good sense of other people's intentions, an out-of-sync network could contribute to the social awkwardness many autistic people exhibit.
It might particularly distort a skill called "theory of mind" -- our ability to figure out what other people are thinking, based on our own thoughts in similar situations.
"If you can't imagine what other people would do in certain situations or would want to have done to them, you can't behave in a socially appropriate way," he said.