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Planet Earth

Rats Compulsively Gamble for Same Reason Humans Do: Lack of Serotonin

80beatsBy Allison BondJune 19, 2009 1:43 AM
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Rats in laboratory tests learned to gamble based on a system of punishments and rewards, strategizing like human gamblers. And when researchers tweaked the animals' brain chemistry to mimic that of humans with a gambling addiction, the mice began taking risks like pathological gamblers, according to a study published in the journal Neuropsychopharmacology. To create this animal model of gambling addiction, researchers created a system in which options that could bring greater rewards also could yield stronger punishment. In this case, however, instead of gambling for money, the rats aimed to get as many sugar pellets as possible. The rodents were placed in specially built boxes whose walls incorporated four "response holes." Each opening was associated with a possibility of earning treats - from one up to four, depending on the aperture chosen. When an animal poked its snout into a hole, the movement would break an infra-red light across the opening, signaling a computer with a "probabilistic" reward-punishment schedule to assign a pellet win or a "timeout" loss. Playing against the clock, the rats had only 30 minutes to accumulate as many sugar pellets as they could

[The Canadian Press]

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The rats quickly caught on that by choosing the openings that offered the greatest number of pellets, they also risked the longest time-outs during which they could not play the game. The test was based on an evaluation for decision-making in humans called the Iowa Gambling Test. In that game, there are some "bad" decks of cards that offer high rewards and punishments, and other "good" decks that offer lesser rewards and punishments. The animals learned that the best way to maximize the number of pellets was to play conservatively, and they began choosing openings that offered fewer pellets but lesser punishments, instead of risking long time-outs for a jackpot of pellets. But when the researchers lowered the rats' levels of serotonin, a chemical associated with impulse control and depleted in addictive gamblers, the rats' decision-making skills were impaired. They began taking bigger risks, just like human pathological gamblers.

"They weren't as good at telling what was the best option anymore," said [co-author] Catharine Winstanley [CBC].

Scientists hope that the correlations between human and rat brain chemistry and gambling behavior put forth by the research will offer clues for treatment of gambling addictions and other impulse control disorders. Says Winstanley: "This coincides with data we've seen from pathological gamblers, who have been shown to have lower levels of serotonin in their brains.... This also ties in neatly with clinical findings in humans"

[BBC].

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