A group of US researchers has produced a robotic set of legs which they believe is the first to fully¹ model walking in a biologically accurate manner. The neural² architecture, musculoskeletal architecture and sensory³ feedback pathways in humans have been simplified and built into the robot, giving it a remarkably⁴ human-like walking gait that can be viewed in this video -- http://www.youtube.com/watch?v=MnD7LqisBhM&feature=youtu.be.

The biological accuracy of this robot, which has been presented July 6, in IOP Publishing's Journal of Neural Engineering, has allowed the researchers to investigate the processes underlying⁵ walking in humans and may bolster⁶（支持） theories of how babies learn to walk, as well as helping⁷ to understand how spinal⁸-cord-injury patients can recover the ability to walk.

A key component⁹ of the human walking system is the central pattern generator¹⁰ (CPG). The CPG is a neural network in the lumbar region（腰部） of the spinal cord that generates rhythmic¹¹ muscle signals. The CPG produces, and then controls, these signals by gathering¹² information from different parts of the body that are responding to the environment. This is what allows people to walk without needing to think about it.

The simplest form of a CPG is a half-centre, which consists of just two neurons that fire signals alternatively, producing a rhythm. The robot contains an artificial half-centre as well as sensors¹³ that deliver information back to the half-centre, including load sensors that sense force in the limb when the leg is pressed against a stepping surface.

Co-author of the study, Dr Theresa Klein, said: "Interestingly, we were able to produce a walking gait, without balance, which mimicked¹⁴ human walking with only a simple half-centre controlling the hips¹⁵ and a set of reflex responses controlling the lower limb."

The researchers, from the University of Arizona, hypothesize that babies start off with a simple half-centre, similar to the one developed in this robot, and over time they 'learn' a network for a more complex walking pattern. This could explain why babies have been seen to exhibit a simple walking pattern when placed on a treadmill¹⁶ even before they have learnt to walk -- a simple half-centre is already in place.

"This underlying network may also form the core of the CPG and may explain how people with spinal cord injuries can regain¹⁷ walking ability if properly stimulated¹⁸ in the months after the injury," Dr Klein continued.