Amyloid Plaques and Tau Tangles Explained: Understanding Alzheimer’s Disease and Modern Diagnosis

Educational illustration of how amyloid plaques (outside brain cells) and tau tangles (inside brain cells) may interfere with brain communication. AI-generated image used for explanatory purposes.

In 1906, Dr. Alois Alzheimer examined the brain of a woman who had experienced early memory loss and confusion. After her death, he found two abnormal protein patterns under the microscope—now known as amyloid plaques and tau tangles.

These two changes are now considered the main physical signs of Alzheimer’s disease in the brain.

To better understand this, it helps to know a simple fact. The brain is made up of billions of tiny cells that communicate with one another. This communication lets us think, remember, speak, and make decisions. When these cells are healthy, the brain works well. But if they get damaged, memory and thinking problems can happen.

Amyloid plaques form outside brain cells. Amyloid is a small protein that the body naturally makes. In healthy brains, it gets cleared away. In Alzheimer’s disease, the brain doesn’t clear it as well. The protein pieces start sticking together. Over time, they form clumps that build up between brain cells. Scientists think this buildup can disrupt communication among brain cells and may cause irritation in the brain.

Illustration: Educational diagram of how amyloid plaques (outside brain cells) and tau tangles (inside brain cells) may interfere with brain communication. Image generated using AI for explanatory purposes.

Tau tangles form inside brain cells. Tau is another protein. It usually helps keep the inside of a cell stable and organized, like support beams. In Alzheimer’s disease, tau changes shape. It twists and clumps together. When this happens, the brain cell can’t work properly and may eventually die.

For a long time, scientists thought amyloid buildup happened first and caused the tau changes. Newer research shows the process might be more complex. Sometimes tau changes show up earlier than expected. Other factors, such as genetics, blood vessel health, inflammation, and overall health, probably also play a role. Alzheimer’s disease isn’t caused by just one problem. It’s a complex process that develops over time.

The amyloid and tau explanation is the current scientific model. While science is evolving, this framework guides diagnosis and treatment. Decades of research have built this understanding, and researchers are still learning how the disease starts and develops.

One big change in recent years is how we diagnose Alzheimer’s disease. In the past, doctors could only diagnose it after clear memory loss appeared. Now, we can sometimes detect amyloid and tau changes earlier. This can be done using blood tests and special brain scans. We are moving toward diagnosing Alzheimer’s based on brain changes, not just symptoms.

This change has also brought new treatments. Some newer medicines target amyloid buildup in the brain. For carefully chosen patients in early stages, these treatments may help slow disease progression. They are not cures. They don’t reverse advanced memory loss. But they are progressing because they focus on brain changes rather than just symptoms.

Having amyloid in the brain doesn’t always mean a person will develop dementia. Some older adults have amyloid deposits but still think clearly. This has led researchers to study cognitive reserve. Cognitive reserve is the brain’s ability to adapt and compensate for cognitive decline. Education, physical activity, social engagement, good sleep, and managing blood pressure and blood sugar may help build resilience. Learn more about how to decrease your risk of dementia.

Alzheimer’s disease is complex, and our understanding continues to grow. The amyloid and tau model has helped move the field forward, allowing earlier detection, clearer diagnosis, and the development of new treatments. As research evolves, our tools and therapies will continue to improve. What matters most is that we are no longer limited to guessing. We can measure biological changes, have informed discussions, and make thoughtful decisions based on the best available evidence.

Written by Marissa Moffitt, Fourth-Year Medical Student

Campbell University School of Osteopathic Medicine

Reviewed by Dr. Golnosh Sharafsaleh, MD

References

• Aizenstein, Howard Jay, et al. "Frequent amyloid deposition without significant cognitive impairment among the elderly." Archives of neurology 65.11 (2008): 1509-1517.

• Jia, Bin, Yun Xu, and Xiaolei Zhu. "Cognitive resilience in Alzheimer’s disease: mechanism and potential clinical intervention." Ageing Research Reviews 106 (2025): 102711.

• Montine, T.J., Cholerton, B.A., Corrada, M.M. et al. Concepts for brain aging: resistance, resilience, reserve, and compensation. Alz Res Therapy 11, 22 (2019).

• Stern, Yaakov. "Cognitive reserve in ageing and Alzheimer's disease." The Lancet Neurology 11.11 (2012): 1006-1012.