Reorganization of Ventral Premotor Cortex After Ischemic Brain Injury: Effects of Forced Use.
Shawn B Frost, Daofen Chen, Scott Barbay and 3 others
PMID 35559809WHAT IT FOUND
Forced use did not clearly add to premotor map expansion beyond lesion size in four squirrel monkeys after motor cortex infarcts, although affected-limb recovery appeared faster than in naturally recovering monkeys.
Key findings
01After 3 months of forced use, the ventral premotor forelimb area increased in all three mapped monkeys, with a mean increase of 77.4 plus or minus 10.9% relative to the pre-infarct area.
02Compared with five naturally recovering monkeys, forced-use monkeys showed a larger percent increase in premotor forelimb area (77.4 plus or minus 10.9%; natural recovery 36.1 plus or minus 9.7%), but the groups differed in infarct size.
03After modelling lesion size, forced use did not significantly add to the predicted premotor area change, and lesion size was the critical factor.
STILL TO COME
How it was doneWhat they found
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What it does not show
The study was done in squirrel monkeys, not people, and the infarct model was not designed to mimic clinical stroke. Only three monkeys were mapped after 3 months of forced use, and the natural recovery comparison used five historical control monkeys rather than a concurrent control group. The forced-use monkeys had larger infarcts than the natural recovery monkeys, so the greater premotor map expansion may reflect lesion size rather than forced use. The animals did not receive intensive rehabilitative training; they wore the constraint device during normal cage behavior and had periodic pellet retrieval tests. Prolonged constraint is not safe or feasible to assume: the authors note potential dysfunction in the constrained limb and cite prior monkey work that reported muscle atrophy and skill deficits after long restriction.
Declared interests
The authors declared no conflict of interest. The listed publication types include non-U.S. government and NIH extramural research support.
The easy way to misread this
Do not conclude that 24 hours/day forced use is a proven treatment for stroke patients. The study was in four squirrel monkeys, and after accounting for lesion size the forced-use effect on premotor maps was not significant. The authors also note that very long constraint may be unfeasible and could cause deficits in the constrained limb.