The right hemisphere controls the left side of the body. Like the left side, it has four lobes called the frontal, temporal, occipital and parietal lobes. The right hemisphere is believed to be involved with spatial relations, calculation and understanding the emotional nuances of speech.
The left hemisphere controls the right side of the body. Unlike the right hemisphere, it includes two regions called Broca's area and Wernicke's area. The Canadian Institute of Neurosciences at McGill University explains that Broca's area is associated with the mechanical production of speech. People with deficits in this area understand language but cannot produce speech. Wernicke's area is associated with decoding and producing intelligible speech. People with deficits in this area can speak, but are not intelligible.
The left hemisphere is connected to its right counterpart by the corpus callosum. The corpus callosum is a thick bundle of nerves that allows information to flow between the hemispheres of the brain. This is why the right side of the brain is also involved in decoding speech.
