Descending neurons coordinate anterior grooming behavior in Drosophila

• Published in: Current biology 2022-02, Vol.32 (4), p.823-833.e4
• Main Authors: Guo, Li, Zhang, Neil, Simpson, Julie H.
• Format: Article
• Language: English
• Subjects: action selection; Animals; Brain - physiology; command neurons; connectomics; descending neurons; Drosophila; Grooming - physiology; grooming behavior; motor control; Motor Neurons - physiology; Movement; neural circuits
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2021.12.055

The brain coordinates the movements that constitute behavior, but how descending neurons convey the myriad of commands required to activate the motor neurons of the limbs in the right order and combinations to produce those movements is not well understood. For anterior grooming behavior in the fly, we show that its component head sweeps and leg rubs can be initiated separately, or as a set, by different descending neurons. Head sweeps and leg rubs are mutually exclusive movements of the front legs that normally alternate, and we show that circuits in the ventral nerve cord as well as in the brain can resolve competing commands. Finally, the left and right legs must work together to remove debris. The coordination for leg rubs can be achieved by unilateral activation of a single descending neuron, while a similar manipulation of a different descending neuron decouples the legs to produce single-sided head sweeps. Taken together, these results demonstrate that distinct descending neurons orchestrate the complex alternation between the movements that make up anterior grooming. [Display omitted] •Anterior grooming normally encompasses alternating front leg movements•Descending neurons can evoke head sweeps or front leg rubs separately or together•Flies resolve conflicting commands by circuits in ventral nerve cord or brain•Left and right leg movements can be decoupled in head sweeps, but not in leg rubs Guo et al. investigate the neuronal control of anterior grooming behavior in Drosophila. Mutually exclusive movements, head sweeps and front leg rubs, can be initiated separately, or as an alternating set, by activation of different descending neurons. In addition, left and right leg movements can be decoupled in head sweeps, but not in leg rubs.