Duke University Medical Center researchers have pinpointed a new marker that may help identify those at greatest risk for cognitive decline and Alzheimer's disease. The Duke researchers used functional magnetic resonance imaging (fMRI) on people with mild cognitive impairment (MCI) to track regions of the brain that become active or inactive when participating in tasks that involve memory.

The researchers focused on an area of the brain known as the posteromedial cortex. The study's lead author, Dr. Jeffrey R. Petrella, theorizes that the posteromedial cortex may be the brain's 'cruise control' that normally deactivates when trying to remember things, allowing resources to be sent to other areas of the brain that encode memories. In people with MCI or Alzheimer's, this deactivation does not happen and the posteromedial cortex remains active.

The fMRI level of deactivation was found to significantly predict which MCI subjects converted to Alzheimer's. Currently, all people with mild memory loss are treated the same, even though some MCI subjects may convert to Alzheimer's in a year and others may take five years. The ability to probe brain circuits at a deeper level may help to diagnose risk with greater certainty.

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