02476nas a2200241   4500008004100000022001400041245011900055210006900174260001200243300001600255490000700271520173900278653001302017653001902030653001602049653002502065653001502090653001602105100002302121700002102144700002102165856004802186       2009                        eng d  a1529-240100aAcquisition of a simple motor skill: task-dependent adaptation plus long-term change in the human soleus H-reflex.0 aAcquisition of a simple motor skill taskdependent adaptation plu  c05/2009  a5784–57920 v293 aActivity-dependent plasticity occurs throughout the CNS. However, investigations of skill acquisition usually focus on cortex. To expand the focus, we analyzed in humans the development of operantly conditioned H-reflex change, a simple motor skill that develops gradually and involves plasticity in both the brain and the spinal cord. Each person completed 6 baseline and 24 conditioning sessions over 10 weeks. In each conditioning session, the soleus H-reflex was measured while the subject was or was not asked to increase (HRup subjects) or decrease (HRdown subjects) it. When the subject was asked to change H-reflex size, immediate visual feedback indicated whether a size criterion had been satisfied. Over the 24 conditioning sessions, H-reflex size gradually increased in six of eight HRup subjects and decreased in eight of nine HRdown subjects, resulting in final sizes of 140 +/- 12 and 69 +/- 6% of baseline size, respectively. The final H-reflex change was the sum of within-session (i.e., task-dependent) adaptation and across-session (i.e., long-term) change. Task-dependent adaptation appeared within four to six sessions and persisted thereafter, averaging +13% in HRup subjects and -15% in HRdown subjects. In contrast, long-term change began after 10 sessions and increased gradually thereafter, reaching +27% in HRup subjects and -16% in HRdown subjects. Thus, the acquisition of H-reflex conditioning consists of two phenomena, task-dependent adaptation and long-term change, that together constitute the new motor skill. In combination with previous data, this new finding further elucidates the interaction of plasticity in brain and spinal cord that underlies the acquisition and maintenance of motor skills.10aH-Reflex10amotor learning10amotor skill10aoperant conditioning10aplasticity10aSpinal Cord1 aThompson, Aiko, K.1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1942024602272nas a2200241   4500008004100000022001400041245007000055210006800125260001200193300001400205490000800219520158400227653001301811653002001824653002501844653001501869653001801884100002301902700002101925700001501946700002101961856004801982       2001                        eng d  a0014-481900aMotor unit properties after operant conditioning of rat H-reflex.0 aMotor unit properties after operant conditioning of rat Hreflex  c10/2001  a382–3860 v1403 aOperant conditioning of the H-reflex produces plasticity at several sites in the spinal cord, including the motoneuron. This study assessed whether this spinal cord plasticity is accompanied by changes in motor unit contractile properties. Thirty-one adult male Sprague-Dawley rats implanted for chronic recording of triceps surae electromyographic activity and H-reflex elicitation were exposed for at least 40 days to HRup or HRdown training, in which reward occurred when the H-reflex was greater than (12 HRup rats) or less than (12 HRdown rats) a criterion value, or continued under the control mode in which the H-reflex was simply measured (7 HRcon rats). At the end of H-reflex data collection, rats were anesthetized and the contractile properties of 797 single triceps surae motor units activated by intraaxonal (or intramyelin) current injection were determined. Motor units were classified as S, FR, Fint, or FF on the basis of sag and fatigue properties. Maximum tetanic force and twitch contraction time were also measured. HRdown rats exhibited a significant increase in the fatigue index of fast-twitch motor units. This resulted in a significant decrease in the percentage of Fint motor units and a significant increase in that of FR motor units. HRup conditioning had no effect on fatigue index. Neither HRup nor HRdown conditioning affected maximum tetanic force or twitch contraction time. These data are consistent with the hypothesis that conditioning mode-specific change in motoneuron firing patterns causes activity-dependent change in muscle properties.10aH-Reflex10amotor unit type10aoperant conditioning10aplasticity10atriceps surae1 aCarp, Jonathan, S.1 aChen, Xiang Yang1 aSheikh, H.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1168131402520nas 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/1009896202267nas a2200253   4500008004100000022001400041245006600055210006300121260001200184300001400196490000700210520156600217653001301783653002501796653001501821653000801836653001801844653002301862100002101885700002101906700002001927700001901947856004701966       1996                        eng d  a0897-715100aOperant conditioning of H-reflex in spinal cord-injured rats.0 aOperant conditioning of Hreflex in spinal cordinjured rats  c12/1996  a755–7660 v133 aOperant conditioning of the spinal stretch reflex or its electrical analog, the H-reflex, is a new model for exploring the mechanisms of supraspinal control over spinal cord function. Both rats and primates can gradually increase (HRup conditioning mode) or decrease (HRdown conditioning mode) soleus H-reflex magnitude when exposed to an operant conditioning task. This study used H-reflex operant conditioning to assess and modify spinal cord function after injury. Soleus H-reflexes were elicited and recorded with chronically implanted electrodes from rats that had been subjected to calibrated contusion injuries to the spinal cord at T8. From 18 to 140 days after injury, background EMG, M response amplitude, and initial H-reflex amplitude were not significantly different from those of normal rats. HRdown conditioning was successful in some, but not all, spinal cord-injured rats. The H-reflex decrease achieved by conditioning was inversely correlated with the severity of the injury as assessed histologically or by time to return of bladder function. It was not correlated with the length of time between injury and the beginning of conditioning. The results confirm the importance of descending control from supraspinal structures in mediating operantly conditioned change in H-reflex amplitude. In conjunction with recent human studies, they suggest that H-reflex conditioning could provide a sensitive new means for assessing spinal cord function after injury, and might also provide a method for initiating and guiding functional rehabilitation.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/900206101790nas a2200229   4500008004100000022001400041245005800055210005600113260001200169300001200181490000800193520117500201653001301376653002501389653001501414653000801429653001801437653001601455100002101471700002101492856004701513       1996                        eng d  a0014-481900aReversal of H-reflex operant conditioning in the rat.0 aReversal of Hreflex operant conditioning in the rat  c11/1996  a58–620 v1123 aIn response to an operant conditioning task, rats can gradually increase or decrease soleus H-reflex amplitude without change in background electromyographic activity or M response amplitude. Both increase (under the HRup mode) and decrease (under the HRdown mode) develop over weeks. The present study investigated reversal of conditioned H-reflex change. Following collection of control data, rats were exposed to one mode (HRup or HRdown) for 50 days, and then exposed to the opposite mode for up to 72 days. Rats responded to each mode exposure with gradual, mode-appropriate change in H-reflex amplitude. This finding is consistent with other evidence that H-reflex conditioning depends on spinal cord plasticity. The effects of exposure to the HRup (or HRdown) mode were not affected by whether exposure followed previous exposure to the HRdown (or HRup) mode. In accord with recent studies suggesting that HRup and HRdown conditioning have different spinal mechanisms, these results suggest that reversal of H-reflex change is due primarily to the superimposition of additional plasticity rather than to decay of the plasticity responsible for the initial change.10aH-Reflex10aoperant conditioning10aplasticity10arat10asoleus muscle10aSpinal Cord1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/895140701682nas a2200229   4500008004100000022001400041245010100055210006900156260001200225300001400237490000800251520101200259653002101271653001301292653001301305653001101318653002501329653000901354100002101363700002101384856004701405       1995                        eng d  a0304-394000aOperantly conditioned plasticity and circadian rhythm in rat H-reflex are independent phenomena.0 aOperantly conditioned plasticity and circadian rhythm in rat Hre  c08/1995  a109–1120 v1953 aRecent studies indicate that rats can increase or decrease H-reflex amplitude in response to an operant conditioning paradigm. In addition, rats also display a circadian rhythm in H-reflex amplitude. As part of the development of H-reflex conditioning in the rat as a new model for defining the plasticity underlying a simple form of learning, this study examined the relationship in the rat between operantly conditioned H-reflex change and the H-reflex circadian rhythm. When H-reflex amplitude increased or decreased in response to the operant conditioning program, its circadian rhythm showed no changes in phase and minimal change in amplitude. Furthermore, animals did not alter daily performance schedule so as to use the rhythm to increase reward probability. Thus, in the rat, H-reflex operant conditioning and the H-reflex circadian rhythm appear to be independent phenomena. The circadian rhythm should not be a significant complicating factor in studies of operantly conditioned H-reflex change.10acircadian rhythm10aH-Reflex10aLearning10aMemory10aoperant conditioning10aRats1 aChen, Xiang Yang1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/7478262