MRI scans have allowed researchers to peer inside the human brain. And the technology is great at revealing damage from a stroke, or areas that light up when we see a face.
But brain scan studies have yet to offer much insight into the underpinnings of traits like intelligence, or mental health conditions like anxiety and depression.
A key reason is that these studies need to include scans of thousands of brains, instead of the dozens typically used, a team reported in the March 16 issue of the journal Nature.
“You need a very large sample, and bigger samples are better,” says Dr. Nico Dosenbach, an author of the study and an associate professor of neurology at Washington University in St. Louis. That’s a lesson the field of genetics has already learned, says Paul Thompson, a neuroscientist at the University of Southern California who was not involved in the research.
Differences in the brain that are associated with mental illness tend to be far less obvious, and far more controversial. For example, some studies have found that people with major depressive disorder have less activity in the brain’s frontal lobe. But the strength of that correlation varies widely from study to study. And there’s no way to look at the activity in any one person’s frontal lobe and know how that person is feeling.
Many brain scientists are still trying to digest the news that human behavior studies may require thousands of scans.
The ENIGMA Consortium, which Thompson helped create, is one effort to make this easy. The group maintains a database with more than 50,000 MRI scans. And scientists have already used that to identify brain differences associated with schizophrenia.
“There’s huge differences all over the brain in schizophrenia,” Thompson says. “The auditory centers that are involved in hallucinations are abnormal. There’s alterations in memory systems, in vision systems.”
But it may take even larger studies to find the brain areas and connections associated with mental illnesses like depression and bipolar disorder because the differences are far more subtle.
Read more at NPR.org.
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