A key area of the brain that controls the mouth, tongue, larnyx and
other intricate movements necessary for speech has been identified for the
first time by a UC Davis researcher.
In a study of 25 stroke patients, neuropsychologist Nina Dronkers found that damage to a region known as the "insula" seems to be a crucial impediment to the motor control necessary for words and sentences. For example, someone with damage to the insula might sound tongue-tied over such words as "tree," pronouncing them instead as "dree" or "free."
"We may have found an area that in the very least is signficantly related to the speech process if not a center for that function," says Dronkers, who conducted the work at the VA Medical Center in Martinez and published her results in a recent issue of the journal Nature.
The insula is a common area of injury in stroke patients, Dronkers says, but not much is known about this part of the brain. Located deep within each hemisphere, the insula is about two inches wide.
The key area for speech articulation seems to be a piece of the left insula about the size of a pencil tip eraser. One step among the many brain processes from generating the concept to uttering the word, this tiny area seems to be necessary for coordinating the sounds of speech.