Johns Hopkins researchers identify two brain regions shrinking up to a decade before Alzheimer's memory loss

Johns Hopkins University researchers examined brain scans from people without symptoms, people with cognitive impairment and patients who later died from Alzheimer's disease. They compared the entorhinal cortex and amygdala with the hippocampus, the memory region most often checked for Alzheimer's damage. In two independent datasets, the entorhinal cortex and amygdala showed greater relative tissue loss in early disease stages. The findings were published in NeuroImage Reports and presented at Neuroscience 2026.

The team used MRI and positron emission tomography scans from the Alzheimer's Disease Neuroimaging Initiative and the Biomarkers of Cognitive Decline Among Normal Individuals study. The study design was observational and longitudinal, following hundreds of participants over time, including patients who later died from the disease. Its key limitation is that earlier shrinkage was associated with Alzheimer's progression, not yet proven as a standalone diagnostic test.

The finding shifts attention from the hippocampus to neighboring regions that support memory retrieval and emotional memory. The entorhinal cortex helps retrieve stored memories, while the amygdala contributes to emotional memory. Because Alzheimer's can accumulate silently for decades, earlier visible atrophy could give clinicians a longer window to identify risk before symptoms become obvious. It also supports the idea that Alzheimer's begins as a staged biological process rather than a sudden clinical event.

Alzheimer's is the most common cause of dementia worldwide, and the study describes symptoms emerging only after long silent progression. If scans can reveal risk years earlier, doctors may be able to intervene while more brain tissue is still intact. For families, that means a possible path to earlier monitoring, care planning and support for people at risk and their clinicians.