An area of the brain that controls language (the
               planum temporale), and has long been designated as
               unique to humans, is revealed to have remarkable
               similarities to that of the same area in chimpanzees. A
               recent study in the medical journal Science reports the
               results of careful measurement techniques that
               compared this area in both species with significant
               and promising results.1

               "Not only are the areas similar in structure and
               appearance, but the area in the left brain of
               chimpanzees is consistently larger and more
               developed than the right. Just as in humans," said
               NIDCD investigator Allen R. Braun, M.D.

               The marked differences in the two sides of the chimp
               brain were first observed during a magnetic
               resonance imaging study that was conducted by two of
               the authors. Following that discovery, this research
               team, led by anthropologist Patrick J. Gannon, Ph.D.,
               of the Mount Sinai School of Medicine, made surface
               measurements of the planum temporale of 18
               chimpanzee brains that were obtained from several
               archived collections. The anatomical markers of the
               region were identified and found to be similar to
               those of humans. The investigators then precisely
               measured both the right and left sides of the brain. In
               94 percent, or 17 of the 18 brains, the left side was
               significantly larger than the right.

               The predominance of this area of the left brain has
               long been felt to be unique to humans, subserving
               functions such as language, handedness, and the
               development of musical talent. The authors suggest
               that their results bring the concept of human
               uniqueness into question and in addition, raise new
               questions. For example, have chimps developed this
               same area for another, yet unidentified, function? Is it
               just by chance that humans developed this area for
               language? Do chimps and humans share a common
               neurological substrate for language? Have
               chimpanzees developed this area for a subtle but
               sophisticated form of gestural communication that has
               not yet been identified by humans?

               "These results also raise the possibility of developing
               an animal model for conditions such as dyslexia and
               schizophrenia, which are predominantly disorders of
               the left temporal lobe of the brain," noted Dr. Gannon.
               "This study will generate language research from a
               new perspective," commented James F. Battey, Jr.,
               M.D., Ph.D., Director, NIDCD.