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.