Spinal advance gets rats running

US, Russian and Swiss scientists were able to train rats with complete spinal cord transection to run on a treadmill. Using a combination of serotonergic agonists and epidural electrical stimulation, they able acutely transform spinal networks from nonfunctional to highly functional and adaptive states. It was found that these interventions could recruit specific populations of spinal circuits, refine their control via sensory input and functionally remodel these locomotor pathways when combined with training. This allowed for full weight-bearing locomotion in paralyzed rats that was almost no different from normal stepping.

Bridging the Gap

Despite having loss of supraspinal input to the lumbosacral spinal circuits due to severe spinal injury (leading to permanent paralysis of the legs), the rat's networks of neurons in the lumbosacral region retain a capability to oscillate and generate coordinated rhythmic motor outputs. Circuits underlying such outputs are commonly referred to as central pattern generators (CPGs). This circuitry can generate close-to-normal hindlimb locomotor patterns in the absence of any supraspinal input. By directly accessing and activating these spinal cord CPGs, scientists were able to facilitate locomotor recovery in the rats after a severe spinal cord injury. The rats were able to carry their own weight at walking and running pace with no differences between their gait and running style of healthy rats.

In their study, it was found that near normal adaptive stepping and standing without any brain input emerged as a result of the capability of spinal neuronal networks to recognize and use task-specific sensory input. They found that "sensory information instantly transformed motor patterns in response to changing task, load, speed and direction conditions with a degree of flexibility and precision that has not been previously observed in animals with spinal cord injury." (1)

Researchers suggested that this strategy could, hypothetically, deliver "substantial levels" of motor control in the legs of humans, although the patient would not have any conscious control of the movement.

Certainly, their findings have important implications for understanding motor pattern formation in the absence of supraspinal input and provides a foundation for the development of strategies to ameliorate motor function in humans after a spinal cord injury and possibly those with neuromotor disorders.

(1) Full Article: http://www.nature.com/neuro/journal/vaop/ncurrent/full/nn.2401.html

(2) News Story: http://news.bbc.co.uk/2/hi/health/8263787.stm

Jonathan Vo