Video 1. Representative recording and processing of descending neuron population activity and animal behavior.

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(Top left) Fly behavior as seen by camera 5. Odor stimulus presentation is indicated. (Middle left) Fictive walking trajectory of the fly calculated using FicTrac. White trajectory turns gray after $2\mathrm{s}$. (Bottom left) 3D pose of the fly calculated using DeepFly3D. Text indicates the current behavior class. (Top right) Raw two-photon microscope image after center-of-mass alignment. (Middle right) $\mathrm{\Delta }F/F$ image after motion correction and denoising of the green channel. (Bottom right) Linear discriminant analysis-based low-dimensional representation of the neural data. Each dimension is a linear combination of neurons. The dimensions are chosen such that frames associated with different behaviors are maximally separated.