Asymmetry of the human cortex. The Sylvian fissure, which defines the upper margin of the temporal lobe, rises more steeply on the right side. The posterior part of the planum temporale, which forms the upper surface of the temporal lobe, is usually much larger on the left side. The enlarged region is part of Wernicke's area, suggesting that the asymmety may be related to the linguistic importance of the left hemisphere.

From N Geschwind, Specializations of the human brain, Scientific American , June1992, p.185.