02294nas a2200193   4500008004100000022001400041245013100055210006900186260001200255300001400267490000700281520166100288653002501949100002101974700002301995700001302018700002102031856004802052       2006                        eng d  a0022-307700aSensorimotor cortex ablation prevents H-reflex up-conditioning and causes a paradoxical response to down-conditioning in rats.0 aSensorimotor cortex ablation prevents Hreflex upconditioning and  c07/2006  a119–1270 v963 aOperant conditioning of the H-reflex, a simple model for skill acquisition, requires the corticospinal tract (CST) and does not require other major descending pathways. To further explore its mechanisms, we assessed the effects of ablating contralateral sensorimotor cortex (cSMC). In 22 Sprague-Dawley rats, the hindlimb area of left cSMC was ablated. EMG electrodes were implanted in the right soleus muscle and a stimulating cuff was placed around the right posterior tibial nerve. When EMG remained in a specified range, nerve stimulation just above the M response threshold elicited the H-reflex. In control mode, no reward occurred. In conditioning mode, reward occurred if H-reflex size was above (HRup mode) or below (HRdown mode) a criterion value. After exposure to the control mode for > or = 10 days, each rat was exposed for another 50 days to the control mode, the HRup mode, or the HRdown mode. In control and HRup rats, final H-reflex size was not significantly different from initial H-reflex size. In contrast, in HRdown rats, final H-reflex size was significantly increased to an average of 136% of initial size. Thus like recent CST transection, cSMC ablation greatly impaired up-conditioning. However, unlike recent CST transection, cSMC produced a paradoxical response to down-conditioning: the H-reflex actually increased. These results confirm the critical role of cSMC in H-reflex conditioning and suggest that this role extends beyond producing essential CST activity. Its interactions with ipsilateral SMC or other areas contribute to the complex pattern of spinal and supraspinal plasticity that underlies H-reflex conditioning.10aSomatosensory Cortex1 aChen, Xiang Yang1 aCarp, Jonathan, S.1 aChen, Lu1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/16598062