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Turning Mice Into Psychopaths at the Flip of a Switch

Scientists have long known that the hypothalamus, sometimes called the “reptilian brain,” is responsible for many basic functions like breathing in addition to being involved with emotions like anger and sexual desire. But Dr. Dayu Lin with the California Institute of Technology has taken our understanding of the hypothalamus’ role a step further by controlling some of it’s functions using light. Through a process called optogenetics, Dr. Lin made certain areas of a mouse’s hypothalamus, specifically a region called the ventrolateral ventromedial hypothalamus (VMHvl), sensitive to light. Using fiberoptic cables, Dr. Lin was able to target these areas and stimulate them with light. The results were immediate and dramatic.

From Discover magazine:

If the mice were alone, nothing happened when Lin shone a light onto their brains. But if they had company, it was a different story. A flash of light, and the mice transformed from Jekylls into Hydes. They rapidly attacked other mice, whether male, female or anaesthetised. They would even assail an inflated glove.

This demonstrated the VMHvl’s power over aggression, but it was apparently not all-powerful. In instances where one of the experimental mice was copulating with a female, the light stimulus had no effect. But afterward, the mouse could be made aggressive again. But the two modes, aggressive and sexual, were not mutually exclusive. Further study reveled that 25% of the neurons involved in sex and aggression were active during both activities. Interestingly, though sex could switch-off the aggression neurons, violence didn’t necessarily switch-off the sexual neurons.

Dr. Lin then took his research a step further, by engineering a virus to prevent the aggressive neurons from firing at all. This rendered 25% of the aggressive mice docile.

Some are already suggesting that this research could form the (morally dubious) grounds for new forms of imprisonment, and other forms of human and animal control. However, this study should be taken on its own merits. It demonstrates the complexity of the brain, how much we know and how much there is yet to find; the connection between the emotional and the physical; and the techniques that we can use to explore the brain further.

That said, I am certain there is a “super-soldier” type Sci-Fi storyline in here somewhere.

(image and story via Discover magazine)

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