Chimpanzees like humans are born with immature forebrains

A study has stated that the portions of the brain that are critical for complex cognitive functions, including decision-making, self-awareness and creativity, are immature at birth in both chimpanzees and humans.

But there are important differences, too. Baby chimpanzees don’t show the same dramatic increase in the volume of prefrontal white matter in the brain that human infants do.

The study is the first to track the development of the chimpanzee brain over time and to make the comparison to humans.

“One of the most marked evolutionary changes underlying human-specific cognitive traits is a greatly enlarged prefrontal cortex,” Tetsuro Matsuzawa of Kyoto University in Japan, said.

“It is also one of the latest-developing brain regions of the cerebrum,” Matsuzawa said.

That built-in developmental delay, now shown to be shared with chimps, may provide an extended period of plasticity, allowing both humans and our closest evolutionary cousins to develop complex social interactions, knowledge and skills that are shaped by life experiences.

“Both humans and chimpanzees need to render their neural network and brain function more susceptible to the influence of postnatal experience,” Matsuzawa said.

Matsuzawa’s team made their discoveries by studying magnetic resonance imaging (MRI) scans of three growing chimpanzees from the age of six months to six years, when chimps reach pre-puberty.

The findings suggest that a less mature and more protracted elaboration of neuronal connections in the prefrontal portion of the developing brain existed in the last common ancestor of chimpanzees and humans.

The study has been reported in the August 11th Current Biology, a Cell Press publication.