Apeing the way we see Faces

Chimpanzees are known to recognise other chimps by their faces, and now researchers have found the part of the brain responsible - and it's basically the same bit of the brain that works in humans!

Understanding how a chimpanzee's brain works is essential to understanding our own.  As our closest relatives, the differences between us and chimps are essentially the differences that make us human.  Publishing in Current biology, John Votaw and colleagues from the Yerkes National Primate Research Centre at Emory University studied Chimpanzee brain activity after getting the Chimps to match pictures of fellow Chimp's faces.  Previous behavioural studies have shown that Chimps appear to process faces in similar ways to us, but this is the first study to look in to the underpinning neural processes.

The researchers used Positron Emission Tomography, or PET scans, to examine brain activity using blood sugar metabolism as a measure of activity.  To test the response to faces, the chimps were shown three pictures of Chimp faces - 2 identical and one different.  They were then asked to pick the two that matched.  To check that the brain activity they saw was face-related, the chimps also performed the same task with non-face clipart images.  The measure of activity for the two tasks was compared with each other and with a resting state, to identify task-specific brain activity.

The results showed significant activity in the brain regions known to be responsible for face recognition in humans - the including superior temporal sulcus, which is over on the side of your brain, above the ear, and the orbitofrontal cortex, which resides at the front of the brain, behind the eyes.  They also recorded face-selective activity in a brain region called the fusiform gyrus, which lights up in response to face recognition in humans.

Faces are such a special case, in fact, that humans have a small region in the brain, called the Fusiform Face Area, or FFA.  The FFA is about 1 cm cubed, and it's exact location varies between individuals.  This particular study found no such area for Chimps, but as the chimpanzee brain is only about one third the volume of the human brain, it may just be hiding.  As previous research has shown a very different pattern of brain activity in response to faces in monkeys, it could be that Chimps and us share a novel way of recognising and responding to faces.