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A Chimp's Emotional Day at the Brain Scanner

By Ross Pomeroy

Electroencephalography, or EEG for short, is the recording of electrical activity along the scalp and is one of the most rudimentary and least invasive forms of measuring brain activity.

Originally used on humans in 1924, EEG has now become fairly routine for mankind. But believe it or not, it was first used on a fully awake adult chimpanzee just four years ago.

Since then, researchers have used EEG to observe chimpanzees' brain activity in response to hearing their own name and seeing faces and objects. Now, in a new study just published to Nature's Scientific Reports, Japanese researchers observed a chimpanzee's brain activity in response to viewing emotional stimuli.

With EEG sensors affixed to her head, the chimpanzee, Mizuki, was shown a variety of pictures. Some of the pictures were deemed "neutral" and displayed chimpanzees simply eating or sitting down. These pictures constituted about 80% of the images displayed. Every so often, researchers would mix in an "affective" picture, in which other chimpanzees were smiling or showing anger. All the while, Mizuki's brain activity was monitored.

The EEG picked up distinct brain activity appearing 210 ms after Mizuki viewed an affective picture, a pattern similar to that in humans. According to the researchers, this may be a manifestation of empathy, which chimpanzees are widely thought to exhibit.

"This suggests that at least a part of the affective process is similar between humans and chimpanzees," the researchers write. "The results have implications for the evolutionary foundations of emotional phenomena, such as emotional contagion and empathy."

Source: Satoshi Hirata, Goh Matsuda, Ari Ueno, Hirokata Fukushima, Koki Fuwa, Keiko Sugama, Kiyo Kusunoki, Masaki Tomonaga, Kazuo Hiraki & Toshikazu Hasegawa (2013) Brain response to affective pictures in the chimpanzee. Scientific Reports 3, Article number: 1342 doi:10.1038/srep01342

Steven Ross Pomeroy is the assistant editor of Real Clear Science. Follow him on Twitter @SteRoPo.

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