Caltech researchers used some innovative techniques on tiny fruit flies to obtain the first recordings of their brain-cell activity while in flight. As you read this, keep in mind the size of a fruit fly - a mere 3 mm in body length. This research is ingenious.
Photo: Gaby Maimon and Michael Dickinson/Caltech
The scientists first clamped the fruit fly's head in place, effectively tethering it while allowing it to flap its wings. They then sliced off a bit of the cuticle covering the brain, and inserted electrodes onto genetically marked neurons.
With the fly and the electrodes in place, the team used a puff of air to stimulate the fruit fly to flap its wings, as if in flight. High speed digital cameras recorded its behavior, while the electrodes measured neural activity.
For this study, the researchers were looking at the visual system of the fly. As they expected, the visual cells immediately ramped up their activity as the fruit fly began to fly. These cells are believed to control the steering muscles during flight.
Michael Dickinson, one of the scientists involved, noted "The neurons' responses to visual motion roughly double when the flies begin to fly, which suggests that the system is more sensitive during flight. The increase is very abrupt. It's not at all a subtle change, and so we suspect that there is a neurochemical quickly released during flight that sets the animal's brain in this different state."
The next step for the research team is to determine what specific mechanism causes the change in sensitivity. With their tethered flight system in place, the scientists also plan to study brain activity involving other types of cells, such as the olfactory and motor cells.