Whether a monkey is looking to the left or merely watching another monkey looking that way, the same neurons in his brain are firing, according to researchers at the Duke University Medical Center.
"We speculate that the neurons' activity may lie beneath critical social behavior, such as joint attention," said Michael Platt, Ph.D., Duke professor of neurobiology and evolutionary anthropology and senior author of the study published in the Proceedings of the National Academy of Sciences. "If social inputs to the neurons are disrupted, that might contribute to the social deficits seen in autism and other disorders."
People spontaneously follow the gaze of other people, and this joint attention helps promote social bonding, enhance learning, and may even be necessary for the development of language. People who can't do these things are at a decided disadvantage, and may fail to develop normal patterns of social interaction, Platt said.
In fact, the impulse to follow the direction of another monkey's eyes was so strong, monkeys sometimes strayed from the assigned light detection task, for which they were rewarded with juice, and instead followed the gaze of a monkey they saw in the projected image.
Previous studies have reported the existence of so-called "mirror" neurons that respond both when monkeys make a particular movement, such as reaching for a peanut, and when the monkeys observe someone else doing the same thing. Given the importance of joint attention and gaze following for both monkeys and humans, many scientists predicted that neurons that mirror observed gaze would be found someday - but until the study by the Duke scientists such nerve cells had never been described.
The attention-mirroring neurons turned out to be located in the parietal lobe, a part of the brain dedicated to eye movements and attention. This is important because it suggests that reading someone else's attention involves the same brain circuits that control one's own attention, Platt said.
In the experiment, the researchers first established whether a particular neuron responded when the monkey himself gazed to the left or to the right. Then they presented the monkey with photos of monkeys randomly looking left or right, thus matching the preferred direction of the neuron on half of trials.