Thursday, October 31, 2013

On Snake Detection Neurons

Primates may have neurons specialized to detect snakes.

In macaque monkeys:
They found that images of snakes had a particularly strong and fast-acting effect on pulvinar neurons: Of the 91 neurons that became active at some point in the experiment, 40% were “snake-best,” meaning they were more active during snake photos than other images. These neurons also fired more frequently than the ones responding to faces, hands, or shapes. (Neurons responding to angry faces, an important social threat for the highly social macaques, came in second.) Finally, snake-responsive neurons sprang into action more quickly, activating about 15 milliseconds faster than those that responded to angry faces and about 25 milliseconds ahead of the neutral shape-detecting neurons.

But, there is always a caution:
The results support the idea that primates have built-in mechanisms for recognizing a very specific threat based on its shape, says Isabelle Blanchette, a cognitive psychologist at the University of Quebec, Trois-Rivières, in Canada who studies the role of emotion in how we process information. But she warns that we should resist the urge to extrapolate to humans. Even if we carry these “leftovers from evolution” in the form of snake-sensitive neurons deep in our visual system, higher brain processes, such as learning and memory, may influence our behavior just as much as this deep and instinctive snake sense. “It’s a very important part of the picture, but it is only a part,” she says. Her research has shown that humans aren’t always faster at detecting snakes than other threats, including guns and cars, which we haven’t evolved to fear innately.