Johns Hopkins Study Finds Alzheimer's Shrinks Two Brain Regions Years Before Memory Loss

BALTIMORE - Researchers at Johns Hopkins University reported on Nov. 14 that Alzheimer's disease triggers detectable shrinkage in the entorhinal cortex and amygdala up to a decade before clinical memory symptoms emerge. What happened? Published in NeuroImage: Reports and presented at Neuroscience 2026, the study analyzed hundreds of MRI and PET scans across two major cohorts. Researchers examined data from the Alzheimer's Disease Neuroimaging Initiative and the Biomarkers of Cognitive Decline Among Normal Individuals study, tracking asymptomatic adults, cognitively impaired participants, and deceased patients. Across both datasets, the entorhinal cortex, which retrieves stored memories, and the amygdala, which processes emotional memory, showed earlier relative tissue loss than the hippocampus, the brain structure doctors typically examine first. Why does it matter? Detecting tissue loss years before cognitive decline could enable earlier preventive treatments when brain cells remain viable. Digital pathology confirmed the gray matter shrinkage overlapped with abnormal tau protein buildup. "We have found that there are early changes in the brain manifesting the clinical biomarkers of atrophy as much as a decade before there are clinical symptoms," senior author Michael Miller said, according to ScienceDaily. Treating neurodegenerative changes at the two-to-four-year mark rather than after 15 years could better preserve memory in high-risk adults. What comes next? The researchers cautioned that more validation is needed before brain imaging of these two regions can serve as a standalone clinical diagnostic test. The team next plans to map molecular changes surrounding early tau accumulation to identify targeted therapies capable of halting tissue loss before severe damage occurs.