Human language has long been believed to be controlled by two primary sections of the left hemisphere of the brain, Broca's area and Wernicke's area. Each area was named for the 19th century physician who discovered its role in communication. Wernicke's area is devoted to receptive language, i.e., reading and hearing. Broca's area processes expressive language, or speech. Recent research, however, has found that the delineation between the two areas may not be that clear.
Broca's area, named in 1861 for French neurosurgeon Dr. Pierre Paul Broca, is located in the left frontal cortex of the brain. It facilitates speech production, producing the initial motor signals that control the vocal cords, tongue, lips, diaphragm and other parts of the body necessary for spoken communication. However, new studies are showing that Broca's area may have a broader role in facilitating human language.
Wernicke's area, named for German neurologist Dr. Karl Wernicke, is located at the end of the temporal lobe of the brain. This area has been credited for receptive language, the ability to receive communication through vision and hearing. To facilitate hearing, for instance, the Wernicke area receives nerve signals from the ears, differentiating words from other sounds. Together the Wernicke area and Broca's area form a language loop that is located in the left hemisphere of the brain in about 90 percent of right-handed people and 70 percent of left-handed individuals.
A scientific study conducted in 2009 at the University of California, San Diego School of Medicine, showed that Broca’s area has a larger role in processing language than previously believed. Scientists used a procedure called Intra-Cranial Electrophysiology (ICE) to record the workings of Broca's area while patients repeated words and used them in various grammatical forms, such as changing tense, actions effortlessly practiced in everyday human conversation. The images produced in the study showed that Broca’s area was involved in controlling both receptive and expressive language, dispelling the common belief that these components of language are exclusive to the different sections of the brain. The study documented neuronal activity indicating that words presented to test subjects were recognized, processed grammatically and prepared for articulation all within Broca's area.