People who are considered at risk for developing Alzheimer’s have abnormal brain function even before they develop amyloid plaques, a study published in the Journal of Neuroscience found.

Investigators conducted functional MRI scans on 100 people whose average age was 62. They discovered that the high-risk participants had a particular form of the apolipoprotein E gene variant called APOE4.  Researchers found that this variant can cause changes in brain function before the amyloid plaques—a key indicator of the disease—start to build up. Amyloid is the protein that makes up the plaques.

Spinal puncture tests also revealed that participants had normal amyloid levels in their cerebrospinal fluid.