Anatomical Study of Cerebral Asymmetry in the Temporal Lobe of Humans, Chimpanzees, and Rhesus Monkeys

TLDR

Anatomical asymmetries in the temporal lobe language region are linked to left‑hemisphere language dominance in humans. The study measured left and right Sylvian fissure lengths in human, chimpanzee, and rhesus monkey brains. Human fissures are longer on the left, chimpanzees show a smaller leftward asymmetry, and rhesus monkeys exhibit no significant left‑right difference.

Abstract

It is generally accepted that anatomical asymmetries in the temporal lobe language region of humans are associated with the asymmetrical representation of language function in the left hemisphere. Comparative measurements were taken of the length of the left and right Sylvian fissures of human, chimpanzee, and rhesus monkey brains. Measurements confirmed the findings of other studies that the human Sylvian fissure is longer on the left than on the right. The chimpanzee brains had a similar asymmetry but to a lesser degree than the human brains. The rhesus brains, however, showed no significant differences between left and right fissure lengths.