The part shown as (3) in the illustration 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. Evidence that this area is involved in the physical articulation of speech comes from work reported in the 1950s by two neurosurgeons, Penfield and Roberts (1959). These researchers found that, by applying small amounts of electrical current to specific areas of the brain, they could identify those areas where the electrical stimulation would interfere with normal speech production.

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