What is Semantic Dementia? - Symptoms & Treatment

Instructor: David White
Dementia affects millions of people and can often be difficult to understand and sometimes impossible to treat. In this lesson, you will learn about one type of dementia- semantic dementia - and explore how some of the symptoms manifest and are treated.

Types of Memory

In the 21st century, we have witnessed amazing discoveries in the medical world that are weakening or eradicating some of the world's worst viruses and diseases. Despite these incredible advances, however, dementia and Alzheimer's disease continue to challenge researchers. There can be many different causes of dementia and a number of theories about how it can be treated. But until a cure is found, the best that we can do is try to understand the signs and symptoms in order to help those diagnosed with the disease.

This lesson focuses on one type of dementia, semantic dementia, which is a neurological disorder that causes a loss of semantic memory over time. Semantic memory is the long-term memory that includes knowledge a person learns outside of personal experience. For example, you know that Columbus set sail for the Indies in 1492 because you learned it at an early age and it is stored in your semantic memory. More broadly, you know how to speak a language because the sounds and meanings of words are also stored in semantic memory.

In order to understand semantic dementia, it's important to be able to differentiate the two important types of memory. The opposite of semantic memory is episodic memory, which includes the things you learn from personal experience. The names of your friends and family members, for example, are stored in your episodic memory. In people with semantic dementia, the episodic memory is generally unaffected.

Memory and Dementia

Given that semantic memory is where we store things like the meaning of words or important facts, you can probably understand why this disease can be so debilitating. For example, imagine that you are about to order a cheeseburger at a restaurant and all of a sudden you can't remember the name of the thing that you wanted to order. If this happens regularly, it can be incredibly frustrating and even frightening.

The forgetting of words and meanings is known as aphasia, and it's the most obvious symptom of semantic dementia. In the early stages of semantic dementia, a person's aphasia might be difficult to detect because it's something that can happen to everyone from time to time. If you're watching television, for example, and you want to change the channel, you might temporarily forget what the thing that changes the channel is called. Over time, however, people with semantic dementia demonstrate not only a loss of the word, but also the meaning. In this case, they wouldn't know what the remote control is called, and they also might not know how to use it.

After a number of years, symptoms begin to show up more often and can become a significant impairment. When aphasia progresses, a person not only begins to 'lose' words temporarily but can also have a hard time understanding what is being said. This is generally because the person is no longer able to recall the meaning of certain words or concepts. If you were speaking to a woman with moderate semantic dementia and asked her to go outside and wait for a cab, she might become very confused because she doesn't know what 'outside' means or is unsure what a 'cab' is.

Aphasia affects a the ability to recall or recreate what ordinary things, like an elephant, look like.

Once the disease is advanced, the person can become profoundly impaired and may not be able to communicate very well, if at all. This is because the individual's ability to recall words and meanings is mostly gone. Additionally, at this late stage, the individual might not be able to recognize certain things like animals or trees, which can be very frightening. For example, imagine if you didn't know what a dog was and it came running up to you. Not only do you not know what it is, but you also don't know whether or not it is going to attack you.


Since semantic dementia affects a person's behavior and ability to understand the meaning of words and concepts, treatment can be difficult. Moreover, semantic dementia causes behavioral and personality changes that can make a person difficult to work with. It is important to remember that people with this condition are unable to control any of what is happening to them.

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