Engineered fruit flies shed light on brain's stop signals

Researchers in Florida have unravelled the precise neuronal mechanisms involved in stopping. Their findings demonstrate how the brain employs different neuronal mechanisms depending on the environmental context.

As reported on the Spider's Web portal, this discovery is intriguing, but the real excitement stems from what was occurring in the brains of these small creatures.

The Florida researchers genetically modified fruit flies to respond to red light. Imagine the flies behaving like a car driver; the insects immediately stopped moving when a light beam hit their eyes.

Stopping is essential for almost all animal behaviours; it's a "critical" action. During foraging, when an animal detects food, it must stop; for example, when it is dirty, it must stop to clean itself. The ability to stop seems simple. However, until now, scientists have not understood this mechanism well because it involves complex interactions with competing behaviours such as walking.

- Purposeful movement through the world relies on halting at the correct time as much as walking. It is central to important behaviours like eating, mating, and avoiding harm. We were interested in understanding how the brain controls halting and where halting signals override signals for walking - says Dr Salil Bidaye from the Institute.

They utilised the power of the fruit fly, which has a simplified nervous system and a short lifespan. Bidaye and his team identified the neurons that initiate stopping.

Using optogenetics, they activated specific neurons by shining red light. In this way, they tested which caused freely walking flies to stop.

The scientists discovered that three unique types of neurons, Foxglove, Bluebell, and Brake, caused the flies to stop upon activation.

The first two neurons were responsible for something they called "Walk-OFF," while the third neuron was responsible for the "Brake" action (Walking disabled and Braking).

The "Walk-OFF" mechanism works by disabling the neurons that drive walking, much like taking your foot off the accelerator in a car.

The "brake" mechanism actively prevents stepping by increasing knee joint resistance and providing postural stability. It also inhibits neurons supporting walking, not just preventing steps.

It appears that Florida scientists' discovery could, in the future, aid in the treatment of neurodegenerative diseases such as Parkinson's disease by precisely manipulating specific neuron activities.

Observers with a more critical view of science fear that such discoveries will eventually lead to a time when we will not only observe but also influence how we think and act.