Alzheimer’s disease may cause degeneration of neurons in the brain through amyloid plaques, neurofibrillary tangles, inflammation, and brain atrophy. The condition may affect different parts of the brain.

Alzheimer’s disease is a condition that causes progressive neurodegenerative damage in the brain.

Neurodegenerative conditions happen when the neurons in your brain deteriorate over time and eventually die.

Neurons are small cells responsible for communicating signals and transmitting energy between different parts of the brain and through neural pathways from the brain to the muscles and organs in the body.

Over time, neurodegeneration from Alzheimer’s may affect the parts of the brain responsible for memory, decision making, physical movement, emotional regulation, and more.

These neurodegenerative changes may also cause your brain to shrink more than people without the condition.

Keep reading to learn more about how Alzheimer’s affects the brain and the parts that may become affected.

The exact cause of Alzheimer’s isn’t yet known, but researchers have found that the abnormal buildup of two proteins in the brain is characteristic of the condition.

Senile plaques

In Alzheimer’s, a protein called beta-amyloid appears in irregular clumps or clusters in the brain. This protein comes from a precursor protein found in a fatty membrane that covers nerve cells.

Clumps of beta-amyloid fragments stick together to form plaques, which are known as senile plaques or amyloid plaques.

According to the National Institute on Aging (NIA), beta-amyloid 42 is the most destructive protein fragment, and people with Alzheimer’s tend to have more amyloid plaques with this protein than people without Alzheimer’s.

Amyloid plaques disrupt signals between synapses, which are the spaces between nerve cells where information passes from one cell to another.

Over time, this disruption may lead to cell death and Alzheimer’s symptoms.

Neurofibrillary tangles

The abnormal buildup of another protein called tau may also contribute to brain neurodegeneration.

In normal brain tissue, tau stabilizes microtubules, which are key parts of cell structure. In Alzheimer’s, however, tau buildup may cause protein strands, or threads, to become tangled. These are known as neurofibrillary tangles.

As a result, the brain system for transporting cell nutrients along parallel structures — which can be compared to railroad tracks — falls apart.

Without these critical nutrients, brain cells die.

Memory and cognition depend on the transmission of signals across billions of neurons and pathways in your brain.

Amyloid plaques and neurofibrillary tangles may interfere with cell signal transmission by affecting the synapse, known as synaptic loss. According to the NIA, a cell can have as many as 7,000 synaptic connections.

When synaptic connections get damaged, the scrambled chemistry produces flawed signaling, so some of the brain’s messages are lost. This could affect your ability to learn, remember, and communicate.

Research suggests that synaptic damage or loss is one of the main signs of cognitive decline in Alzheimer’s.

Some research suggests that neuroinflammation may contribute to neurodegeneration.

Glial cells are a type of brain cell that helps protect, support, and maintain the healthy function of neurons, according to the NIA. The three types of glial cells are microglia, astrocytes, and oligodendrocytes.

Microglia initiate immune responses in the brain to clear away foreign substances, such as beta-amyloid plaques.

If microglia cells don’t work properly, however, a buildup of unhealthy glial cells may stimulate neuroinflammation, which could lead to neurodegeneration.

According to the NIA, Alzheimer’s may also reduce the glucose and blood circulating in the brain, which your cells need to produce energy to function.

A short supply of blood and glucose in the brain may cause oxidative stress that could lead to neuroinflammation and, in turn, neurodegeneration.

Some Alzheimer’s research focuses on how this inflammatory response can be reduced or managed.

Research suggests that in advanced Alzheimer’s, some parts of the brain may wither and shrink, known as brain atrophy.

In particular, brain atrophy can be seen in the hippocampus, the part of your brain most responsible for memory and decision making.

Neurodegeneration, including the loss of synapses, neurons, and glial cells, may be the primary cause of brain atrophy.

The brain is a complex organ responsible for everything from physical movement and function to processing information, senses, language, logic, emotions, and more.

The brain comprises several different regions that are defined as four lobes on each side.

According to the Alzheimer Society of Canada, the effects of Alzheimer’s may correspond to the areas of degeneration in the brain.

Hippocampus and temporal lobe

The first signs of neurodegeneration are usually in the entorhinal cortex. This is near the hippocampus, which is located below the temporal lobe.

The hippocampus is located in the middle of your brain. It’s responsible for storing and processing memories, as well as making judgments and decisions.

Since the hippocampus is the first region to be affected by Alzheimer’s, this may be why some of the early symptoms of Alzheimer’s include:

  • memory loss, such as forgetting where you placed something
  • difficulty remembering names, places, or faces
  • difficulty completing usual tasks
  • difficulty speaking or processing language

Frontal lobes

These two lobes are located at the front of your brain. They play a key role in making decisions, planning, and engagement. When Alzheimer’s affects this lobe, you may experience behavioral changes like:

  • loss of interest in things you once enjoyed
  • social withdrawal
  • repeating actions over and over

Parietal lobes

The parietal lobes play a key role in sensory processing, spatial awareness, and the orderly performance of tasks.

When Alzheimer’s affects this lobe, you may experience several behavioral changes, such as difficulty:

  • performing daily tasks, including driving, eating, and putting on your clothes
  • understanding others
  • expressing your thoughts and emotions
  • walking or performing physical tasks

Occipital lobe

The occipital lobe is located at the back of the brain and is responsible for processing visual information. It’s one of the last regions in the brain to be affected by Alzheimer’s.

If this region in your brain is affected by Alzheimer’s, you may experience difficulty processing colors, shapes, and sizes, as well as gradual vision loss.

Alzheimer’s disease is a neurodegenerative condition that causes progressive damage to the neurons in your brain.

Although there’s no cure for Alzheimer’s, some treatments can help protect the neurons in your brain to slow the progression of the disease.

Consider speaking with a healthcare professional if you or someone you know experience symptoms of Alzheimer’s. They could provide a proper diagnosis and develop an appropriate treatment plan.