This recently published paper is from a Seattle-based team who are using the same type of non-invasive stimulation that Project Spark is clinically trialing in Australia. They are also looking to improve arm and hand function for quadriplegics.
The video footage linked below shows encouraging results. There are four short one minute videos that show before and after with patients on the trial who gain meaningful movement in their hands. Please note, these patients were incomplete AIS-C injuries to start with but the improvements are never-the-less life-changing:
https://drive.google.com/drive/folders/1jZXAQzeuhlf6g2qTUtuQbQt3GPOY8Jir?usp=sharing
Notes to the video footage:
Supplementary movie 1. Immediate effect of stimulation. Participant 3 had C5 level AIS C category injury 12 years prior to beginning the study.
He was not using his right arm or hand for any daily activities. During training alone, function of his right hand did not improve. On the first day of
stimulation, however, he was able to pick up, transport and release 3.8 cm ping-pong balls easily.
Supplementary movie 2. Near-term and sustained improvement in precision grip were enabled by stimulation. Prehension grip performance did
not improve during 12 sessions of training alone. On the second day of stimulation, Participant 3 was not able to pinch 1.3-cm diameter marbles
before the stimulator turned on. After a few minutes of stimulation, however, he was able to grasp, transport and release this size marble for the
first time since his injury. The audio captures his reaction to this rapid improvement with biphasic stimulation at 45mA. Precision grip performance
continued to improve, such that he could pick up small beads (0.5 cm) by the end of the stimulation treatment and after 3-months of follow-up
without further stimulation or training.
Supplementary movie 3. Reduced muscle tone and spasticity resulting from stimulation treatment. Participant 5 had C5, AIS C injury 2.5 years
prior to beginning the study. High tone in her finger flexor muscles made it impossible to open her hand to grasp objects. Training alone did not
reduce the muscle tone, and she was still unable to grasp 2.5 cm wooden blocks. Starting from the first week of stimulation, the participant
experienced a gradual reduction of spasticity that allowed her to grasp and transport 2.5 cm blocks. Several days later, she could also grasp and
release these blocks with much greater precision. Additional stimulation enabled her to open her fingers and thumb a greater distance to grasp 7.5
cm wooden pegs. This reduced spasticity and increased function was present both during and between stimulation sessions.
Supplementary movie 4. Stimulation restored fine motor skills of the paralyzed hand. Before the study, Participant 3 was not able to isolate and
rapidly coordinate his left finger movements, and his right thumb could not move to strum the guitar. Stimulation paired with training restored his
volitional control of thumb and individuated finger movements on both hands and motivated him to resume his hobby of playing the guitar for the
first time in 12 years since injury. This improvement in motor skills allowed him to both depress the strings to the frets, and rapidly form many
musical cords. He continued to practice playing guitar throughout the study, and his improved dexterity persisted for at least six months after
stimulation.