Code from: Sensory feedback and central neuronal interactions in mouse locomotion

Locomotion is a complex process involving specific interactions between
the central neural controller and the mechanical components of the system.
The basic rhythmic activity generated by locomotor circuits in the spinal
cord defines rhythmic limb movements and their central coordination. The
operation of these circuits is modulated by sensory feedback from the
limbs providing information about the state of the limbs and the body.
However, the specific role and contribution of central interactions and
sensory feedback in the control of locomotor gait and posture remain
poorly understood. We use biomechanical data on quadrupedal locomotion in
mice and recent findings on the organization of neural interactions within
the spinal locomotor circuitry to create a tractable mathematical model of
mouse locomotion. The model includes feedback signals characterizing the
load and extension of each limb as well as postural stability. We
investigate several model versions and compare their behavior to existing
experimental data. Our results highlight specific roles of sensory
feedback and some central propriospinal interactions between circuits
controlling fore and hind limbs for speed-dependent gait expression. Our
models suggest that postural imbalance feedback may be critically involved
in the control of swing-to-stance transitions in each limb and the
stabilization of walking direction.