Why Does Language Break Down in Dementia?
The frontal and temporal lobes need to work together for language to function.
Posted Jul 21, 2019
We listen to sounds coming out of someone’s mouth and turn it into meaning so often and so easily we hardly ever think about it. But when we visit a foreign country and cannot understand the language, we are reminded of how miraculous our ability to understand speech really is.
Similarly impressive is our ability to express our meaning to another person through uttering sounds. In this article, we will learn how language works, and why it breaks down in aging and dementia.
Comprehension difficulties can be due to many factors, including poor hearing.
The first step to comprehend spoken language is to hear it through our ears. Hearing deficits, also called deafness, are common as one gets older. They may be simply due to the buildup of wax in the ear canal, which a primary care provider or their staff can easily remove. Ear infections can disrupt the eardrum or other parts of the middle ear, which may be permanently damaged if not treated promptly. A common cause of deafness associated with aging is so-called “sensorineural hearing loss,” due to damage or deterioration of the inner ear and the nerves that carry the impulses to the brain. Hearing aids can help sensorineural hearing loss.
The temporal lobes connect words with their meanings.
After we hear the word correctly, it is the outer and bottom parts of the temporal lobes that decipher its meaning. The temporal lobes are next to your temples, just behind your eyes. This part of the brain understands not only words, but also who and what people and things are, including how you might categorize them. There is a gradient of knowledge in the temporal lobes, such that people (Mary, friend from school; John, colleague at work; Susan, my sister) are in the front, animals (poodle, pet; lion, zoo animal; chicken, farm animal) are in the middle, and human-made objects (desk, office furniture; baseball bat, sports equipment; hairbrush, morning routine) are in the back. This stored knowledge forms the basis of the vocabulary we draw from when we speak.
Whereas the left temporal lobe stores the name of the person or object, the right temporal lobe stores what qualities things have—such as whether they are large or small, light or heavy, hard or soft. So, if the temporal lobes are not working correctly, there will be impairment in both understanding and producing language.
The frontal lobes turn that meaning into words and grammatical sentences.
The frontal lobes coordinate the activity of speaking. They first choose the idea or content we wish to express. They then connect to the temporal lobes to find the words we want to say. Finally, a special part of the left frontal lobe turns the words into sounds and also puts the words into grammatical sentences.
Problems with word-finding are common in all stages of dementia.
Word-finding difficulties are extremely common in dementia, even in the mild stages. Whereas in normal aging, there is difficulty coming up with the names of people, places, books, movies, and other proper nouns, in dementia, there is often difficulty coming up with ordinary, common nouns of everyday things. These difficulties may manifest as the wrong or less precise term being used (for example, flower for rose, table for desk) or, more commonly, simply by pauses in sentences when the word is searched for. Friends and families often get used to jumping in during these pauses to provide the missing word.
Damage to the frontal lobes, the temporal lobes, and the connections between them are all very common in dementia. It can take effort, even for healthy individuals, to find the precise word we’re looking for. That’s why when an individual is tired or sick or otherwise not at their best, it can be particularly hard to find the right word—especially when one has dementia.
Key Question: My husband can’t seem to remember anything I tell him, but he can’t hear anything either. How can I tell if his memory difficulties are really due to a hearing problem?
- If you’re not sure if your loved one’s hearing is impaired, get it checked out with a hearing test. If their hearing is impaired, make sure they use hearing aids or other methods to enhance their hearing.
- One simple way to help make sure that your loved one heard you correctly is to ask them to repeat back what you just told them. Repeating it back will also help them to remember it!
More on language in dementia in my next blog!
© Andrew E. Budson, MD, 2019, all rights reserved.
Budson AE, O’Connor MK. Seven Steps to Managing Your Memory: What’s Normal, What’s Not, and What to Do About It, New York: Oxford University Press, 2017.
Budson AE, Solomon PR. Memory Loss, Alzheimer’s Disease, & Dementia: A Practical Guide for Clinicians, 2nd Edition, Philadelphia: Elsevier Inc., 2016.