A new study published in the journal Science has shown that fruit flies (Drosophila sp.) think before they act.
The fruit fly, Drosophila melanogaster. Image credit: Botaurus.
Scientists at the University of Oxford observed 20 fruit flies make a choice between two concentrations of an odor presented to them from opposite ends of a narrow chamber, having been trained to avoid one concentration.
When the odor concentrations were very different and easy to tell apart, the flies made quick decisions and almost always moved to the correct end of the chamber. When the odor concentrations were very close and difficult to distinguish, the flies took much longer to make a decision, and they made more mistakes.
The researchers found that mathematical models developed to describe the mechanisms of decision making in humans and primates also matched the behavior of the fruit flies.
They discovered that fruit flies with mutations in a gene called FoxP took longer than normal flies to make decisions when odors were difficult to distinguish – they became indecisive.
They tracked down the activity of the FoxP gene to a small cluster of around 200 neurons out of the 200,000 neurons in the brain of a fruit fly. This implicates these neurons in the evidence-accumulation process the flies use before committing to a decision.
“Before a decision is made, brain circuits collect information like a bucket collects water. Once the accumulated information has risen to a certain level, the decision is triggered. When FoxP is defective, either the flow of information into the bucket is reduced to a trickle, or the bucket has sprung a leak,” said study lead author Dr Shamik DasGupta.
Fruit flies have one FoxP gene, while humans have four related FoxP genes. Human FoxP1 and FoxP2 have previously been associated with language and cognitive development. The genes have also been linked to the ability to learn fine movement sequences, such as playing the piano.
“We don’t know why this gene pops up in such diverse mental processes as language, decision-making and motor learning. However, one feature common to all of these processes is that they unfold over time. FoxP may be important for wiring the capacity to produce and process temporal sequences in the brain,” said senior author Prof Gero Miesenböck.
“FoxP is not a language gene, a decision-making gene, even a temporal-processing or intelligence gene.”
“Any such description would in all likelihood be wrong. What FoxP does give us is a tool to understand the brain circuits involved in these processes.”
“It has already led us to a site in the brain that is important in decision-making.”
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Shamik DasGupta et al. FoxP influences the speed and accuracy of a perceptual decision in Drosophila. Science, vol. 344, no. 6186, pp. 901-904; doi: 10.1126/science.1252114
