An Automated Test of Rat Forelimb Supination Quantifies Motor Function Loss and Recovery After Corticospinal Injury.
Anil Sindhurakar, Samuel D Butensky, Eric Meyers and 6 others
PMID 27530125WHAT IT FOUND
In rats, an automated knob-turning task detected large forelimb supination loss after corticospinal tract injury, while a standard pellet reaching success rate did not change.
Rats partially recovered over 6 weeks but remained impaired.
Key findings
01The knob task detected a large loss of supination after pyramidal tract injury, with success falling from 90.3 ± 2.1% to 14.1 ± 7.8% in week 1 and 34.3 ± 11.5% by week 6.
02Rats' pellet reaching success stayed at 55.4 ± 11.1% and did not significantly change for six weeks after injury, although supination quality was impaired.
03Motor cortex inactivation reduced knob supination success from 83.8 ± 1.4% at baseline to 40.9 ± 13% with low dose and 9.8 ± 3.7% with high dose, while pellet reaching success did not change significantly.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study was done in rats, not people, so it does not show how therapists should assess or treat human patients. The number of animals was small, and different tasks used different subsets of rats. The pyramidal tract lesion damaged both direct corticospinal connections and indirect brain stem pathways, so the test does not prove supination loss was specific to the corticospinal tract. Knob turning is not a natural rat movement and required intensive training, so the behavior may not map simply to human hand function. Recovery after injury likely mixed spontaneous recovery with training effects, and some individual rats recovered nearly fully while others remained impaired.
Declared interests
The authors declared that JBC received a one-time consulting fee from Vulintus, Inc., which is developing behavioral tests used in this research under an NINDS SBIR grant. JBC owns no shares and has no financial interest in Vulintus. AMS and RLR own shares in Vulintus, and AMS is employed by Vulintus. AMS and RLR participated in device design but did not take part in data collection, analysis, or manuscript preparation. The article is also listed as supported by NIH extramural research.
The easy way to misread this
Do not conclude that this test is ready for human patients or that it proves corticospinal tract function specifically. The study was conducted in rats, the lesion also damaged indirect pathways, and the task required extensive training.