Emergence of functionally aberrant and subsequent reduction of neuromuscular connectivity and improved motor performance after cervical spinal cord injury in Rhesus.
Gregory Wai, Sharon Zdunowski, Hui Zhong and 12 others
PMID 37378049WHAT IT FOUND
Upper limb muscle activity became excessive and poorly coordinated early after cervical spinal cord injury in four Rhesus monkeys, then partly normalized over 24 weeks as stepping and grape retrieval improved.
Key findings
01Muscle activation was consistently and markedly increased early after cervical spinal cord injury during treadmill stepping.
02Co-contraction between agonist and antagonist muscles during locomotion rose after injury, then returned toward near pre-lesion levels by the chronic phase in subjects 1, 2, and 4.
03Three of four subjects were near pre-lesion success on grape retrieval at the end of the 24-week period, and maximum treadmill speed recovered to near pre-lesion levels.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study used four Rhesus monkeys, not human patients, so it cannot be treated as clinical evidence for people with spinal cord injury. The animals all received surgery, post-operative analgesic and antibiotic care, task retraining, and exercise cage activity together, so the contribution of any single component cannot be separated. The study compared the same animals before and after injury, not a group of untreated animals. Recovery varied widely between animals; Subject 4 could pull only the least stiff spring and generated much smaller forces than before injury. The authors could not attribute the changes in functional connectivity to a specific anatomical mechanism. The Discussion proposes mechanisms such as sprouting, axonal re-growth, synaptic changes, and pruning, but the data do not demonstrate them.
Declared interests
The study was supported by the National Institutes of Health (NS42291), the Veterans Administration, and the California Roman-Reed Funds; no competing interest declarations are given in the supplied text.
The easy way to misread this
Do not conclude that a specific rehabilitation method caused the improved motor performance. The monkeys received surgery, post-operative analgesic and antibiotic care, task retraining, and exercise cage activity together, so the contribution of any single component cannot be separated.