Locomotor-State Dependence of Neuromodulation During Avian Free Flight

Complex avian locomotor behaviors depend on the coordinated operation of neural processes involved in sensory perception, decision-making, and motor execution. Exogenous neural stimulation can alter motor output by intervening in neural processes, but its effects may depend on the current locomotor state. Here, we investigated the locomotor-state dependence of formatio reticularis medialis mesencephali (FRM) microstimulation in freely flying pigeons. Individualized stimulation parameters were screened under stable laboratory conditions and kept constant during free-flight experiments. Flight-state features before and during stimulation were extracted, and state-response models were constructed to quantify their associations with stimulation-evoked turning responses. Results showed that flight state during stimulation was more closely associated with turning responses than pre-stimulation state, with acceleration during stimulation making the largest contribution. When acceleration during stimulation was above the individual mean, turning-response dispersion decreased by 32.92%. In addition, pre-stimulation angular velocity was positively associated with acceleration during stimulation, indicating that the pre-stimulation locomotor state contains information related to the consistency of subsequent stimulation-evoked responses. These findings demonstrate that the effects of FRM microstimulation are locomotor-state dependent and provide a basis for identifying appropriate neuromodulation timing and improving response stability under complex locomotor conditions.