The Physiology of Dementia: What’s Going on Inside the Brain


If you are reading this article, you probably already have some experience with dementia and the way it looks or maybe even feels when you or someone close to you is starting to experience its first signs and symptoms. Forgetfulness, anxiety, disorientation, having trouble with everyday activities–these manifestations are all too familiar to everyone who is dealing with this mysterious disease of the brain. On the outside, dementia can be quite straightforward. Yet what is actually happening inside the brains of dementia patients?

The Changing Brain

Experts studying the brain now know that a lot is happening inside our heads in terms of the growth and death of brain cells, which are called “neurons”. For a long time, however, scientists believed that our brains stopped growing once we reached a certain age. They thought that from that point on, the only way was down, and that was not possible to form new neurons after one’s thirties–or even earlier. In other words, it was thought that the brain grew and grew for many years, and then the growth completely halted, and from that point on, the only changes were the loss or death of neurons. As research methods grew more sophisticated, scientists quickly discovered that their previous thinking on this was completely wrong. They found that the brains of normal–or “neurotypical”–people continued to grow throughout their whole lives, and that one of the most important parts of healthy brain functioning is the delicate ratio between new growth and dying neurons.

What Happens when Dementia Strikes?

Dementia is a category of brain diseases, so the causes of the apparent symptoms is hidden in the brain. Something changes so that the brain can’t function normally anymore–but what?

We already know that the neurotypical brain never stops growing, although cell loss is always happening too. In a brain affected by the most common type of dementia–Alzheimer’s Disease–new cells stop forming. Not only that; a process called neurodegeneration starts. This means that the neurons in the affected person’s brain start to lose their structure and function and may even die. The result of this is shrinking of the brain, called atrophy. It takes place mostly in the part of the brain that is responsible for memory and orientation, the hippocampus. To this day scientists don’t know exactly why this happens or how to stop or reverse this process of neuron death.

Another major cause of dementia is Vascular Dementia. Blood vessels are a vital structure for normal brain functioning, for they deliver food and oxygen to the brain. Our brains get damaged if something happens to these blood vessels because the oxygen supply is interrupted. We call that a stroke. Neurons stop functioning properly or die in the part of the brain that was damaged. The resulting symptoms depend on the part of the brain where the stroke happened. Vascular dementia is often the result of multiple strokes that have happened over time.

To understand another common type of dementia, Dementia with Lewy Bodies, we have to understand what is happening inside the dying neurons. That was not possible until scientists inspected the brains of people with Lewy Body Dementia who passed away. A man called Frederic Lewy (hence the name) looked at the neurons of the deceased peoples’ brains and found chunks of matter inside the neurons, which he later discovered were pieces of protein. Those protein deposits, the so-called Lewy bodies, form plaques and tangles inside neurons, which cause neuron loss in various brain regions and also affect dopamine-producing neurons. That is why we can notice symptoms similar to Parkinson’s disease in people affected by Lewy Body Dementia.

Note: Dopamine is a neurotransmitter; that is, it is a chemical substance that transmits signals between two neurons. Dopamine is involved in motor control, which means that our bodies need it for normal movement and muscle coordination.

Neuron Loss

 This article has covered only three of the most common types of dementia. Although, looking at their physiology, they vary vastly, they have one thing in common: regardless of the underlying cause, the brain starts to degenerate and neurons are lost. Depending on the part of the brain which is affected, the person starts to think, feel, and behave differently. Albeit we currently have no cure for any type of dementia, more and more information about it is discovered every day and may one day lead to a beneficial treatment for all those affected by this brain disease.



Pinel, J. P. J. and Barnes, S. J. (2014). Introduction to Biopsychology. London: Pearson Education Limited.

About the Author

Lara Šuštar is a writer with a Master’s degree in psychology and has been actively working in her field since 2015. She has been working voluntarily with children and adults for five years and most recently switched to assisting at a neurology clinic. Her interests vary vastly, from autism, meditation, impact of food and fitness to neuropsychology. She currently resides in Slovenia, Europe