How Alzheimer’s and Dementia Change the Brain
The brain contains tens of billions of neurons that process and transmit information. These neurons communicate not just between different parts of the brain, but with muscles and organs too.
Dementia affects the connections between these neurons, resulting in a reduction in brain function and gradual cell death. These factors lead to the consequences of dementia that most people are familiar with — memory loss, reduced ability to live independently, heightened emotional responses, and more.
Up until recently, the only way to see changes in the brain was to examine it after death. However, current brain scans can reveal regions of decreased activity or loss of brain tissue while the individual is still alive. Doctors can use these brain scans along with symptoms that the patient is experiencing to reach a diagnosis. In this article, we will go over some of the changes that happen in a brain affected by dementia.
What is the impact of Alzheimer’s and other dementias on the brain?
In healthy aging, the brain will shrink, but not lose a substantial amount of neurons. In the case of Alzheimer’s, however, many neurons will cease to function and lose connection with other neurons. Alzheimer’s is the most common type of dementia, which is characterized by the accumulation of abnormal protein deposits called amyloid plaques and tau tangles in the brain.
These deposits can interfere with the communication between brain cells, leading to a breakdown in neural pathways, which eventually causes brain cells to die.
Alzheimer’s disease often damages neurons in memory-related areas of the brain, such as the entorhinal cortex and hippocampus. It then affects parts of the cerebral cortex that control language, logic, and social interaction. Many other parts of the brain are eventually affected as well. That is why an individual with Alzheimer’s disease progressively loses their capacity to function independently over time.
What makes up a brain cell?
A cell body, several dendrites, and an axon are the three main components of most neurons.
- The nucleus, which holds the genetic code that controls and regulates the cell’s activity, is housed in the cell body.
- A dendrite is a branch-like structure on the surface of a neuron that receives data from neighboring neurons.
- Signals are sent to other neurons by the axon, a cable-like structure at the end of the cell body.
How Alzheimer’s affects regions of the brain
The hippocampus, which is involved in forming new memories and acquiring new knowledge, is usually impacted first in Alzheimer’s disease. This can make it difficult for patients to remember recent events or conversations and may cause them to repeat themselves. However, the hippocampus is less critical for recovering memories from a long time ago. This is why a person may remember childhood experiences but forget what they had for breakfast that morning.
The amygdala, which processes emotions, is typically impacted later in the course of the disease. As a result, individuals with Alzheimer’s may retain emotional memories for longer than factual memories. This emotional memory retention can lead to heightened emotional reactions towards certain people or places, even if the specific details surrounding the experience are forgotten. It’s important to remember that emotional memory retention is not unique to Alzheimer’s disease and can occur in other conditions or situations, such as post-traumatic stress disorder (PTSD) or highly emotional events.
Alzheimer’s disease can also affect the visual system in the temporal lobes, leading to difficulty recognizing familiar people or objects. However, the auditory system may still function, allowing individuals to recognize familiar people through their voice.
As the disease progresses to the frontal lobes, individuals may have difficulty with decision-making, planning, and organizing tasks. Complex activities with multiple steps, such as following a new recipe, can become challenging.
Despite these losses, individuals with Alzheimer’s disease and other dementias may retain talents and skills learned long ago. Procedural memories, which are responsible for learned abilities such as playing an instrument or dancing, are typically preserved deep within the brain and may remain intact for longer than other types of memories. These types of abilities are almost always retained the longest through the course of the disease.
Vascular contributions to Alzheimer’s disease
People with dementia often have more than just Alzheimer’s-related changes in their brains. Various issues involving blood vessels, such as deposits in brain arteries, hardening of the arteries, and mini-strokes, can also be a factor.
These vascular issues can reduce blood flow and oxygen to the brain, and can weaken the blood-brain barrier that usually protects the brain from harmful substances while allowing glucose and other essential nutrients to enter. When the blood-brain barrier is not working properly, glucose cannot reach the brain, and harmful proteins like beta-amyloid and tau can build up in people with Alzheimer’s disease.
This causes inflammation, which can worsen vascular issues in the brain. Because Alzheimer’s disease may both cause and result from vascular problems in the brain, researchers are searching for ways to break this convoluted cycle.
Alzheimer’s disease with Lewy bodies
A person with dementia with a Lewy body (DLB) frequently has less overall shrinkage than someone with Alzheimer’s or Frontotemporal Dementia. Instead, small protein deposits (Lewy bodies) may be seen throughout the cerebral cortex, limbic system, and brain stem.
Early damage in DLB is evident in visual pathways and, in some studies, even in the frontal lobes. This might explain why vision and focus issues are early signs of DLB. Common symptoms of Lewy body dementia also include hallucinations, movement disorders, and cognitive decline.
Parkinson’s disease is also associated with movement abnormalities caused by Lewy bodies in the brain stem.
What happens when brain cells deteriorate?
When brain cells deteriorate and die, the brain shrinks substantially in certain places.
This was discovered by Alois Alzheimer while studying the brain of Auguste Deter, the first person to be formally diagnosed with Alzheimer’s disease. It is still seen in people with the condition today.
Conclusion
As neurons are affected and die across the brain in Alzheimer’s disease, connections between networks of neurons may break down, and areas of the brain begin to shrink. This process, known as brain atrophy, is pervasive in the last stages of Alzheimer’s disease, resulting in considerable brain volume loss.
As a caregiver, it can be challenging to understand what is happening to their brain as you see your loved one experiencing these symptoms. But there are many strategies that can empower you to provide the best possible care for your loved one with dementia. These may include creating a calm and structured environment, using memory aids and other tools to support communication, and engaging in activities that promote cognitive stimulation and social interaction. Check out our other blog posts for methods on how to best support your loved one through the course of their disease.
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