02520nas a2200253   4500008004100000022001400041245007700055210007100132260001200203300001400215490000700229520179900236653001302035653002502048653001502073653000802088653001802096653002302114100002102137700002102158700002002179700001902199856004802218       1999                        eng d  a0897-715100aOperant conditioning of H-reflex increase in spinal cord–injured rats.0 aOperant conditioning of Hreflex increase in spinal cord–injured   c02/1999  a175–1860 v163 aOperant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of long-term supraspinal control over spinal cord function. Primates and rats can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) the H-reflex when reward is based on H-reflex amplitude. An earlier study indicated that HRdown conditioning of the soleus H-reflex in rats is impaired following contusion injury to thoracic spinal cord. The extent of impairment was correlated with the percent of white matter lost at the injury site. The present study investigated the effects of spinal cord injury on HRup conditioning. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from 14 rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. At the lesion epicenter, 12-39% of the white matter remained. After control-mode data were collected, each rat was exposed to the HRup conditioning mode for 50 days. Final H-reflex amplitudes after HRup conditioning averaged 112% (+/-22% SD) of control. This value was significantly smaller than that for 13 normal rats exposed to HRup conditioning, in which final amplitude averaged 153% (+/-51%) SD of control. As previously reported for HRdown conditioning after spinal cord injury, success was inversely correlated with the severity of the injury as assessed by white matter preservation and by time to return of bladder function. HRup and HRdown conditioning are similarly sensitive to injury. These results further demonstrate that H-reflex conditioning is a sensitive measure of the long-term effects of injury on supraspinal control over spinal cord functions and could prove a valuable measure of therapeutic efficacy.10aH-Reflex10aoperant conditioning10aplasticity10arat10asoleus muscle10aspinal cord injury1 aChen, Xiang Yang1 aWolpaw, Jonathan1 aJakeman, L., B.1 aStokes, B., T.  uhttp://www.ncbi.nlm.nih.gov/pubmed/10098962