Usually, when walking, it is the command from the brain that is transmitted to the feet through the spine, and the secret of the feet 'movement
1. Step on one foot first
2. So it stimulates the walking center in the spine
Signal to the other foot
3. The other foot will cooperate due to reflex action
But for people who can't walk, the brain's instructions can't be transmitted to the feet（
The reason why the feet can interact with each other is not because of instructions from the brain
But when one foot moves, the "primitive walking center" of the spine is stimulated and automatically
Give instructions to the other foot, so the feet can move with each other.
This phenomenon is called neuromodulation.