Researchers at the School of Medicine are one step closer to unlocking the secrets of the brain. Michael Greicius, assistant professor of neurology, and his colleagues say that mental states can be identified using patterns of activity in the human brain’s coordinated “networks.”

Their findings, published today in Cerebral Cortex, may advance the effort to create diagnostic tests for various brain disorders, such as Alzheimer’s disease. Greicius and his team used brain-imaging data to figure out which of four mental states their subjects were engaged in — remembering events of the day, doing mental math, relaxing or singing silently to themselves.

Unlike other studies that use time-controlled techniques, the Stanford study allowed experimental subjects to carry out the mental activities at their own natural pace. This new method is the standard fMRI procedure with a twist and enables researchers to understand what the human brain does in free-flowing mental states.

“With standard fMRI, you need to know just when your subjects start focusing on a mental task and just when they stop,” Greicius said in a press release. “But that isn’t how real people in the day-to-day world think.”

Using fMRI scans from 14 men and women, Greicius’ team concentrated on networks of brain regions that activate together during a given mental state. The team made maps of coordinated brain activity for each state, examining 90 brain regions that constituted most of the brain’s gray matter.

With this mental mapping complete, the researchers attempted to identify which among the four mental tasks subjects were performing and correctly predicted them with 80-percent accuracy.

The Stanford investigators hope that this advance will be helpful in determining cognitive disorders. Greicius and his peers previously demonstrated that different disorders show up on fMRI scans with deficiencies specific to different brain networks.

Identifying Alzheimer’s disease stands out as one possible application. The brain network associated with memory is impaired among people with Alzheimer’s disease, a fact that could prove using in conjunction with the findings by Greicius and his colleagues.

— An Le Nguyen