The thoughts and ideas are there.
The words to express those thoughts and ideas can be elusive, however.

For more than two million Americans, this condition is the result of a neurological disorder known as aphasia, most often caused by a stroke. Aphasia does not affect intelligence, but can affect a person’s ability to speak, write or understand language.
For years, students and faculty in UW-Eau Claire’s Department of Speech, Language, and Hearing Sciences have researched various forms of aphasia in an effort to help these individuals communicate more effectively.

