Figure 3. The connectivity of hook and claw neurons is structured to impact activity of leg motor neurons.

(A) We developed an impact score that takes into account monosynaptic, disynaptic, and trisynaptic connections between FeCO axons and leg motor neurons (see methods). (B) Schematic of the 18 muscles controlling the fly’s front leg. Numbers correspond to motor module labels in panel C. (C) Motor impact scores of claw and hook axons on leg motor modules. Motor modules are functional groupings of motor neurons that receive common synaptic input and act on the same joint²⁷. The target muscles of each motor module are indicated in panel B. (D) Motor impact scores of club axons on leg motor modules. Note the scale bar change from panel C. (E) Motor impact scores of FeCO axons onto take-off related motor circuits. The peripherally synapsing interneuron is a premotor neuron involved in takeoff. The tergotrochanter is a leg muscle that is not active during walking but is instead involved in jumping and takeoff ^26,43,44. (F) Motor module preference scores (gray, top) and FeCO subtype preference scores (green, bottom) for each premotor VNC neuron that receives input from FeCO axons (columns). Premotor neurons are arranged according to their preferred motor module followed by their preferred FeCO subtype. (G) Motor module preference (y-axis) plotted against FeCO subtype preference (x-axis) for each premotor VNC neuron that receives input from FeCO axons. (H) Schematic representation of the predominant connectivity pattern seen between FeCO neurons and motor modules. Premotor neurons postsynaptic to the FeCO are primarily dedicated to relaying information from a particular FeCO subtype to a particular motor module.