Alzheimer's Brain: What Happens In A Brain With Alzheimer's Disease?

Updated March 21, 2023by BetterHelp Editorial Team

Aging typically brings with it many physical, cognitive, and even emotional changes. Many people are concerned about the increased risk of health problems and specific ailments. While some of these can be treated and managed with medical care, dementia, and Alzheimer’s disease are two conditions that are generally not so quickly addressed. Both situations involve changes in the brain that affect memory and cognitive functioning. It is essential to know Alzheimers facts to understand this progressive disease clearly.

Normal Brain Vs. Alzheimer's Brain

You likely know that the brain is your body's most influential and arguably most critical organ. This is because it runs all the other parts of your body, allows you to think, retains your memories, and governs your personality. The average brain weighs approximately three pounds. Its texture is similar to a firm jelly substance. It is  comprised of three main parts:

  • The cerebrum is the most significant part of the brain. It is the part that controls cognitive functions such as problem-solving, remembering, thinking, and feeling. It also contains the ability to move.

  • The cerebellum is located at the back of the head, just below the brain. It controls the ability to balance and controls general coordination.

  • The brain stem is located below the cerebrum and in front of the cerebellum. It serves to connect the brain and spinal cord and is responsible for controlling crucial automatic body functions. These include breathing, heart rate, blood pressure, and digestion.

Like the other body parts, your brain is given oxygen from your blood. In fact, with every heartbeat, the arteries carry approximately 20 to 25% of the blood in the body to the brain. The brain has billions of cells that need a good portion of the oxygen found in the blood. Ultimately, your brain uses 20% of the oxygen in the blood. When you are intently concentrating, your brain will use up to 50% of the oxygen flowing through your body.

All that oxygen is needed because of the billions of cells in your brain, a critical job. Those brain cells constantly work to keep you alive and carry out various cognitive processes. Various parts of the brain are dedicated to different, specific tasks. Examples of different functions include processing outside stimuli, interpret sensations, make plans, initiate action, and moving the body.

Of particular importance in dementia and Alzheimer’s disease, the hippocampus is a part of the brain that transfers information into long-term memory. It is a part of the brain's limbic system that assists with giving knowledge and forming memories. Memories are stored in the temporal lobes of the brain. Damage to the hippocampus can impair the ability to create memories.

How Does Alzheimer's Affect The Brain?

No matter what part of the brain is in action, the brain's work is done by individual cells. Branches connect these nerve cells or neurons. The units are technically called axons. Signals can travel along these axons to carry messages from one neuron to another. Unfortunately, in a brain with Alzheimer's disease, the neurons can become damaged and are eventually destroyed. This can disrupt and impair the way that signals can move through the brain.

Researchers think this neuron damage happens because of two processes. One is the formation of neurofibrillary tangles. These are made up of twisted strands of the protein tau. The tau is supposed to be in lines or tracks to transport nutrients. However, it collapses into tangles. This means that nutrients can no longer go to the nerve cells, which causes them to die. 

Second, beta-amyloid plaques, abnormal cluster protein fragments, also build up between the brain's nerve cells. Research indicates these plaques block signaling in the brain's nerve cells.

Scientists are not entirely sure what causes all these changes. However, some changes appear to result from genetic and environmental factors. For example, research shows that a genetic mutation can increase levels of risk. Studies have also found that a head injury sustained earlier in life may also increase the risk of developing Alzheimer’s disease.

What Part Of The Brain Does Alzheimer's Affect?

As noted above, the hippocampus is the part of the brain responsible for putting information into long-term memory. This part of the brain is necessary for this process. If the hippocampus becomes damaged, it can severely affect memory. Generally, after hippocampal damage, people are unable to form new memories. This can result in individuals living in the past if they still can get old memories. Consequently, this can result in individuals living only in the present, as they may immediately forget information.

Alzheimer’s disease is the single most common cause of dementia and, according to the DSM-5, accounts for 60 to over 90% of all cases. Alzheimer’s disease affects the hippocampus first. This part of the brain is also the most severely affected by the condition. The disease then moves through several stages, with symptoms worsening over time as the neuron damage spreads throughout the brain's cortex. This is why memory is often the first cognitive function to be affected in an affected brain, and over time other functions are also acted as the damage increases to affect all parts of the brain eventually.

How Is Alzheimer's Disease Diagnosed?

Brain scans and similar procedures can sometimes help doctors diagnose Alzheimer’s disease, as can a presentation of relevant symptoms. As neurons send signals to the brain, it leads to thoughts and behaviors. This neuronal firing also creates memories and plays a role in the display of personality. Neurons often fire in patterns for certain activities. These patterns can be seen in brain scans, such as a Positive Emission Tomography Scan (or PET Scan as it is called for short). If someone's brain is scanned while doing different activities (such as reading versus solving math problems), different activity patterns can be observed.

Dementia or Alzheimer's brain scan results would show different patterns than what might be expected from a healthy brain. This is because of the changes in neuron function due to the damage from the plaques and tangles that have been building up in the brain. 

However, Alzheimer’s disease may not be able to be diagnosed by a brain scan alone. This is because other disorders and conditions could also account for those changes in brain activity. It can also be tricky to determine what’s truly going on in the brain while a person is living. Historically, Alzheimer’s disease was generally diagnosed with certainty after a person passed away

As a result, sometimes the best course of action is to perform tests to rule out other potential conditions. When no other diagnosis fits the symptoms, then a diagnosis of Alzheimer’s disease can be used to label the condition. Genetic testing may also show a genetic mutation that could support the diagnosis, although that is also not always definitive.

After death, as part of an autopsy, if doctors suspect Alzheimer’s disease, they can examine slices of the brain under a microscope. When this is done, the doctor may observe fewer nerve cells and synapses than is typical. They may also see the tangles and plaques indicative of the disease.

How To Receive Professional Support

If you’ve received an Alzheimer’s diagnosis, are close to someone who has, or are generally concerned about your health, it can be beneficial to speak to both a doctor and a mental health professional for insight. Receiving a proper diagnosis and adequate support can help you feel better prepared to address any changes that might come your way.

Suspecting a diagnosis of dementia or Alzheimer’s disease can be upsetting. Once a diagnosis is confirmed, there can be grief, anxiety, and depression about the situation. Someone in this situation may seek therapeutic support to help them adjust and cope. Frequently, those with dementia and Alzheimer’s disease will eventually rely on family as caregivers. Whether you’re living with Alzheimer’s yourself or are close to someone who is, you may be able to benefit from services like online therapy. This allows you to get the care you may need at a time and from a place that works for you. Whether it be from the comfort of your own home, the office, or somewhere else that brings you peace, you can have control over the environment therapy takes place in.

Aside from its accessibility, online therapy also offers the perk of being a truly beneficial treatment option. A recent review of 17 studies focused on the benefits of online cognitive behavioral therapy found that it could be equally and perhaps even more effective than in-person counseling for treating depression. The same review also observed that online therapy is generally more cost-effective for clients than traditional options.


A brain affected by Alzheimer’s disease is generally subject to damage over time as the disease begins to impact the cells found within each area of the brain. This process generally begins with the hippocampus, the area responsible for memory, and can spread to other regions over time, affecting movement, cognition, speech, and more. Seeking professional care if you believe you may be experiencing symptoms like these can be critical, as can receiving the support of a mental health professional.

For additional help & support with your concerns

The information on this page is not intended to be a substitution for diagnosis, treatment, or informed professional advice. You should not take any action or avoid taking any action without consulting with a qualified mental health professional. For more information, please read our terms of use.
Get the support you need from one of our therapistsGet Started