PT  - JOURNAL ARTICLE
AU  - Pratt, Brandon G.
AU  - Lee, Su-Yee J.
AU  - Chou, Grant M.
AU  - Tuthill, John C.
TI  - Miniature linear and split-belt treadmills reveal mechanisms of adaptive motor control in walking <em>Drosophila</em>
AID  - 10.1101/2024.02.23.581656
DP  - 2024 Jan 01
TA  - bioRxiv
PG  - 2024.02.23.581656
4099  - http://biorxiv.org/content/early/2024/02/24/2024.02.23.581656.short
4100  - http://biorxiv.org/content/early/2024/02/24/2024.02.23.581656.full
AB  - 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 alters step kinematics of flies walking on the linear treadmill across all speeds, while inter-leg coordination remains intact. We also found that flies can maintain a forward heading on a split-belt treadmill by adapting the step distance of their middle legs. Overall, these new insights demonstrate the utility of miniature treadmills for studying insect locomotion.Competing Interest StatementThe authors have declared no competing interest.Body lengththe distance between the head and distal part of the abdomen.Body heightthe vertical distance between the ground and thorax.Step frequencythe number of steps completed within a second.Stance durationthe duration that a leg contacts the ground while walking.Swing durationthe duration of the aerial phase of leg movement during walking.Step lengththe total distance a leg travels within a step (i.e. stance onset to the subsequent stance onset) in allocentric coordinates.Step distancethe total distance a leg travels within a step (i.e. stance onset to the subsequent stance onset) in egocentric coordinates.Step speedthe total distance a leg travels within a step in egocentric coordinates divided by the duration of the step.Anterior extreme positionthe position where a leg first contacts the ground (i.e. stance onset) in egocentric coordinates.Posterior extreme positionthe position where a leg first takes off from the ground (i.e. swing onset) in egocentric coordinates.Number of legs in stancethe number of legs contacting the ground at a given moment in time.L1 relative phasethe relative offset in the stance onsets between the left front leg and the leg of interest with respect to the left front leg’s step cycle.Tripod step orderthe order in which the legs within a tripod group (i.e. ipsilateral front and hind legs and the contralateral middle leg) first enter stance with respect to the left front leg’s step cycle.