
Neuromodulation of spinal networks enables stepping after complete paraplegia - bookofjoe
https://doi.org/10.1038/s41591-018-0175-7
======
jdc
Is anyone familiar with the literature able to ELI5?

~~~
GW150914
Essentially they’re talking about using electrical stimulation to restore
function in people with complete paralysis of the legs due to injury of the
spinal cord in the lower back (lumbar region). In particular they’re focused
on injury to the junction of the lumbar spine and sacrum. The result has been
a restoration of function such that people who previously had no control over
their lower body could (when lying on their side) make motions as though
walking, and walk while suspended from a support rig.

More exciting is that after 43 weeks of this stimulation and comprehensive
training, they were able to walk on a treadmill unassisted bearing their own
weight! It sounds like balance issues and strength remain potentially
problematic, but it’s still amazing. The last line of the introduction really
sums it up:

 _To our knowledge, this is the first report of independent stepping enabled
by task-specific training in the presence of EES by a human with complete loss
of lower extremity sensorimotor function due to SCI._

SCI = Spinal Cord Injury

~~~
blennon
Something to add to this that most non-neuroscientists don't realize is that
the spinal cord is not just a bundle of wires that connect the brain to
muscles. The spinal cord is a complex circuit that contains "central pattern
generators" (CPG) that can produce rhythmic movement. When activated, these
networks can be pushed into a dynamic state where they repeat the same
movement repeatedly, e.g. walking. For more, look up the work by Sten Grillner
on stingray CPGs.

One approximate way of looking at this is that the brain's motor cortex sends
a "go" signal to the spinal cords CPGs and these start generating the signals
to the muscles to walk. You can also think of motor control as hierarchical
where as you go up the hierarchy. The bottom of the hierarchy are the
muscles/actuators, then the neurons that stimulate the muscles, then the
circuits in the spinal cord that have these CPGs and other "primitives", then
primary motor cortex and further up the cortical hierarchy. At the higher
levels of the cortical hierarchy are representations of whole movements, like
moving your hand to mouth. As you descend the hierarchy, the neural signals
control gradually more details components of the movement. For more, look up
the work by Michael Graziano.

~~~
DoubleCribble
Are CPG the source of "muscle memory", ie reflexive actions? So much of
physical training is to achieve the vaunted muscle memory as it allows
unconscious (ie faster) reaction times.

~~~
hanniabu
I would argue that muscle memory has less to do with speed or strength and
more to do with 'remembering' motion. But of course this is just based off
personal experience and intuition so I have nothing to back this up.

