A well-written press release on a very well done and exciting study:
In a study published in 2007, Robinson and his colleagues reported that treatment with octopamine caused foraging honey bees to dance more often. This indicated that octopamine played a role in honey bee dance behavior. It also suggested a framework for understanding the evolution of altruistic behavior, Robinson said.
"The idea behind that study was that maybe this mechanism that structures selfish behavior - eating - was co-opted during social evolution to structure social behavior - that is, altruistic behavior," he said. "So if you're selfish and you're jacked up on octopamine, you eat more, but if you're altruistic you don't eat more but you tell others about it so they can also eat."
But it was not even known if insects have a bona fide reward system. That question led the researchers to study the effects of cocaine on honey bee behavior. Cocaine - a chemical used by the coca plant to defend itself from leaf-eating insects - interferes with octopamine transit in insect brains and has undeniable effects on reward systems in mammals, including humans. It does this by influencing the chemically related dopamine system.
Dopamine plays a role in the human ability to predict and respond to pleasure or reward. It is also important to motor function and modulates many other functions, including cognition, sleep, mood, attention and learning.
One aspect of reward in the human brain involves altruistic behavior, Robinson said. Thinking about or performing an altruistic act has been found to excite the pleasure centers of the human brain.
"There are various lines of thought that indicate that one way of structuring society is to have altruistic behavior be pleasurable," he said.
Because cocaine causes honey bees to dance more - an altruistic behavior - the researchers believe their results support the idea that there is a reward system in the insect brain, something that has never before been shown.
To determine whether the cocaine was merely causing the bees to move more or to dance at inappropriate times or places, the researchers conducted a second set of experiments. These tests showed that non-foraging honey bees don't dance, even when exposed to cocaine. They showed that foragers on cocaine do not move more than other bees (except when dancing), and that they do not dance at inappropriate times or in locations other than the dance floor.
The researchers also found that the bees on cocaine do not dance every time they go on a foraging excursion. And, most important, their dances are not distorted.
"It's not like they're gyrating wildly on the dance floor out of control," Robinson said. "This is a patterned response. It gives distance information, location information. That information is intact."
In a final experiment that also shows parallels to human behavior, the researchers found that honey bees on cocaine experience withdrawal symptoms when the drug is withheld.
"This study provides strong support for the idea that bees have a reward system, that it's been co-opted and it's now involved in a social behavior, which motivates them to tell their hive mates about the food that they've found," Robinson said.
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