"There are no laboratory tests to diagnose migraines depression bipolar disorder and many other ailments of the brain. Doctors typically gauge such illnesses based on selfreported symptoms and behavior. Now a new study shows that a kind of brain scan called functional connectivity MRI fcMRI  which shows how brain regions interact  can reliably detect fundamental differences in how individual brains are wired. As such the technique potentially could be used to distinguish healthy people from people with brain diseases or disorders and provide insight into variations in cognitive ability and personality traits. The findings are published April  in Neuron. This is a step toward realizing the clinical promise of functional connectivity MRI said senior author Steven Petersen PhD the James S. McDonnell Professor of Cognitive Neuroscience in Neurology and a professor of neurosurgery of biomedical engineering of psychological and brain sciences and of radiology. Before we can develop diagnostic tests based on fcMRI we need to know what it is actually measuring. We show here that its not measuring what youre thinking but how your brain is organized. That opens the door to an entire new field of clinical testing. Petersen postdoctoral researcher and first author Caterina Gratton PhD and colleagues analyzed a set of data collected by the Midnight Scan Club a group of Washington University scientists who took turns undergoing myriad scans in an MRI machine late at night when the demand for such machines and consequently the usage fees tend to be low. The researchers analyzed data from more than  hours of fcMRI scans on each of nine people collected in  separate onehour sessions for each person. During the scans each person performed tasks related to vision memory reading or motor skills or rested quietly. Functional MRI scans generate a dynamic map of the outer surface of the brain showing changing hot spots of activity over time. To create a functional connectivity map Gratton divided the brains surface into  regions and identified areas that became active and inactive in unison. She then constructed brain network maps for each individual showing patterns of correlation between parts of the brain. The sheer quantity of data available on each person allowed her to analyze how much an individuals brain networks changed from day to day and with different mental tasks. The answer Not much. Brain networks captured by fcMRI are really about the individual Gratton said. Whether someones watching a movie or thinking about her breakfast or moving her hands makes only a small difference. You can still identify that individual by her brain networks with a glance. The consistency of the fcMRI scans makes them a promising diagnostic tool. Although the techniques potential to identify brain disorders and diseases was noted years ago fcMRIbased diagnostic tests have yet to make their way into doctors offices. Progress has been stymied by confusion over whether the scans reflect fundamental stable features of the brain or if they change with every passing thought. Further the researchers found that the technique was powerful enough to distinguish people who were extraordinarily alike. All of the scanned brains belonged to young healthy scientists and doctors. We need more data before we can know what is normal variation in the population at large Gratton said. But the individual differences were really easy to pick up even in a population that is really very similar. Its exciting to think that these individual differences may be related to personality cognitive ability or psychiatric or neurological disease. Thanks to this work we know we have a reliable tool to study these possibilities."