What Happens in the Brain in Alzheimer’s Disease?

problems between neurons in the brain decimate alzheimer's patients

By Jonny Lupsha, Wondrium Staff Writer

Sufferers of Alzheimer’s disease face a number of difficult symptoms. Memory loss is just one, alongside the inability to perform familiar tasks. What happens structurally to the brain of an Alzheimer’s patient?

Alzheimer's disease: the amyloid-beta peptide accumulates to amyloid fibrils that build up dense amyloid plaques.
In Alzheimer’s disease, the amyloid-beta peptide accumulates to amyloid fibrils that build up dense amyloid plaques. Photo by Juan Gaertner / Shutterstock

Alzheimer’s disease is a particularly cruel thief. It steals its sufferers’ memories; robs them of their relationships with their loved ones; and, ultimately, takes their lives. Alzheimer’s patients slowly experience the loss of their faculties, becoming less independent, struggling to comprehend the passage of time, and exhibiting hoarding behavior.

A new Alzheimer’s drug called donanemab has shown to reduce patients’ cognitive and functional decline by targeting a pathological protein called amyloid-beta that may be the main driver in Alzheimer’s disease. But what is particularly happening to the structures of the brain during Alzheimer’s disease? In her video series Understanding Disorders of the Brain, Dr. Sandy Neargarder, Professor of Psychology at Bridgewater State University, explains what happens in the brain of an Alzheimer’s patient.

What Does Alzheimer’s Do to the Brain?

“Research shows that two hallmark features signal the presence of Alzheimer’s disease: amyloid plaques and neurofibrillary tangles,” Dr. Neargarder said. “Amyloid plaques are abnormal deposits of a protein fragment called beta-amyloid, and they tend to develop between neighboring neurons in the brain, where they interfere with the neurons’ ability to communicate with one another.

“So basically, amyloid plaques disrupt the signals that the brain is trying to send and receive.”

Neurofibrillary tangles are tangles of nerve cells found inside neurons that look like twisted strings. They’re caused by a protein called tau, which normally supports and stabilizes nerve cells. However, in Alzheimer’s cases, these tangles kill the neurons they occupy.

“The accumulation of amyloid plaques and neurofibrillary tangles results in widespread atrophy of the brain,” Dr. Neargarder said. “Basically, the brain shrinks dramatically. This atrophy then causes the symptoms associated with Alzheimer’s disease.”

This is not to say that all amyloid plaques and neurofibrillary tangles are bad. On the contrary, we all have them in our brains right now and we all develop them as we age. The difference between the healthy brain and the Alzheimer’s brain lies in the amount of plaques and tangles.

Alzheimer’s also decreases the production of acetylcholine, which is a neurotransmitter that the brain uses to communicate between neurons. Acetylcholine plays a role in learning and memory, which might explain how it’s related to a pathology of those processes in Alzheimer’s patients.

How Is Alzheimer’s Disease Diagnosed?

“Alzheimer’s disease is typically diagnosed through the process of elimination,” Dr. Neargarder said. “If a patient is exhibiting possible symptoms, a primary care physician will perform a complete physical; order blood work; perhaps consult a CT or MRI scan; and examine the patient’s mental status, medications, and family history.”

According to Dr. Neargarder, as other diagnoses are eliminated, a doctor will give a diagnosis of “probable Alzheimer’s” to a patient and their loved ones. Unfortunately, Alzheimer’s is generally confirmed only through an autopsy, when the patient’s number of amyloid plaques and neurofibrillary tangles can be counted.

Meanwhile, research has shown how the brain’s atrophy, caused by the amyloid plaques and neurofibrillary tangles, presents itself. During the process of elimination for what brain disorder a patient suffers from, the areas of the brain that atrophy rules out other disorders. Depending on which disorder of the brain a patient has determines which areas of the brain develop atrophy.

Understanding Disorders of the Brain is now available to stream on Wondrium.

Edited by Angela Shoemaker, Wondrium Daily