Scientists built mini treadmills for insects – not to keep them fit but to study their walking

Amazing stuff!

Don't laugh! Too bad, humans do not have a middle leg! 😊

"... The researchers were able to track fly walking over long periods of time. Split-belt treadmills were used to investigate how the flies reacted to belts with different speeds on either side of the body. ...

Split-belt treadmills had little effect on the coordination between legs. But the step distances of their middle legs changed a lot. ..."

From the highlights and abstract:

"Highlights

•A new actuated treadmill system captures 3D kinematics of flies compelled to walk

• Flies walking on the treadmill have similar kinematics to freely walking flies

• Proprioceptive feedback is important for leg motor control at all walking speeds

• Flies on a split-belt treadmill use their middle legs to counteract perturbations

Summary

To navigate complex environments, walking animals must detect and overcome unexpected perturbations. One technical challenge when investigating adaptive locomotion is measuring behavioral responses to precise perturbations during naturalistic walking; another is that manipulating neural activity in sensorimotor circuits often reduces spontaneous locomotion. To overcome these obstacles, we introduce miniature treadmill systems for coercing locomotion and tracking 3D kinematics of walking Drosophila. By systematically comparing walking in three experimental setups, we show that flies compelled to walk on the linear treadmill have similar stepping kinematics to freely walking flies, while kinematics of tethered walking flies are subtly different. Genetically silencing mechanosensory neurons altered step kinematics of flies walking on the linear treadmill across all speeds. We also discovered that flies can maintain a forward heading on a split-belt treadmill by specifically adapting the step distance of their middle legs. These findings suggest that proprioceptive feedback contributes to leg motor control irrespective of walking speed and that the fly’s middle legs play a specialized role in stabilizing locomotion."

Scientists built mini treadmills for insects – not to keep them fit but to study their walking "Fruit flies on treadmills are giving scientists insights into how insects walk in ways that previous, more invasive techniques could not"

Miniature linear and split-belt treadmills reveal mechanisms of adaptive motor control in walking Drosophila (open access)

Figure 1. The linear treadmill controls locomotor speed and enables tracking of 3D kinematics in walking Drosophila