Brain Structures and Language Processing Centers

Neurolinguistics: Language and Brain Function

The study of the relationship between language and the brain is called neurolinguistics. Although this is a relatively recent term, the field of study dates back to the nineteenth century.

Since that time, a number of discoveries have been made about the specific parts in the brain that are related to language functions. We now know that the most important parts are located in areas above the left ear.

Anatomy of Language Processing

In order to describe these areas in greater detail, we need to look more closely at some of the gray matter. If we conceptually dissect the brain—removing hair, scalp, skull, disconnecting the brain stem (which connects the brain to the spinal cord), and cutting the corpus callosum (which connects the two hemispheres)—we are basically left with two parts: the left hemisphere and the right hemisphere.

Key Language Centers

The most important language centers are located in the left hemisphere. These include:

• Broca's Area (1): Involved in speech production.
• Wernicke's Area (2): Involved in speech comprehension.
• Motor Cortex (3): Controls articulatory muscles.
• Arcuate Fasciculus (4): Connects Wernicke's and Broca's areas.

Broca's Area (Anterior Speech Cortex)

The part shown as (1) is technically described as the anterior speech cortex or, more usually, as Broca's Area. Paul Broca, a French surgeon, reported in the 1860s that damage to this specific part of the brain was related to extreme difficulty in producing speech.

It was noted that damage to the corresponding area on the right hemisphere had no such effect. This finding was first used to argue that language ability must be located in the left hemisphere and since then has been treated as an indication that Broca's Area is crucially involved in the production of speech.

Wernicke's Area (Posterior Speech Cortex)

The part shown as (2) is the posterior speech cortex, or Wernicke's Area. Carl Wernicke was a German doctor who, in the 1870s, reported that damage to this part of the brain was found among patients who had speech comprehension difficulties.

This finding confirmed the left hemisphere location of language ability and led to the view that Wernicke's Area is part of the brain crucially involved in the understanding of speech.

The Motor Cortex

The part shown as (3) is the motor cortex, an area that generally controls movement of the muscles (for moving hands, feet, arms, etc.). Close to Broca's Area is the part of the motor cortex that controls the articulatory muscles of the face, jaw, tongue, and larynx.

The Arcuate Fasciculus

The part shown as (4) in the illustration is a bundle of nerve fibers called the arcuate fasciculus. This was also one of Wernicke's discoveries and is now known to form a crucial connection between Wernicke's and Broca's areas.

The Localization View

Having identified these four components, it is tempting to conclude that specific aspects of language ability can be accorded specific locations in the brain. This is called the localization view.

The localization view has been used to suggest that the brain activity involved in hearing a word, understanding it, and then saying it, would follow a definite pattern:

1. The word is heard and comprehended via Wernicke's Area.
2. This signal is then transferred via the arcuate fasciculus to Broca's Area, where preparations are made to produce it.
3. A signal is then sent to part of the motor cortex to physically articulate the word.