Researchers have shown for the first time that the protein BRCA1 is required for normal learning and memory and is depleted by Alzheimer's disease. BRCA1 is a key protein involved in DNA repair, and mutations that impair its function increase the risk for breast and ovarian cancer. The new study demonstrates that Alzheimer's disease is associated with a depletion of BRCA1 in neurons and that BRCA1 depletion can cause cognitive deficits.