02242nas a2200241   4500008004100000022001400041245008800055210006900143260001200212300001400224490000800238520154300246653002401789653001301813653001501826653001501841653001601856100002301872700002101895700001501916700002101931856004801952       2001                        eng d  a0014-481900aOperant conditioning of rat H-reflex affects motoneuron axonal conduction velocity.0 aOperant conditioning of rat Hreflex affects motoneuron axonal co  c01/2001  a269–2730 v1363 aThis study assessed the effects of operant conditioning of the H-reflex on motoneuron axonal conduction velocity in the rat. After measurement of the control H-reflex size, rats were either exposed for at least 40 days to the HRup or HRdown conditioning mode, in which reward occurred only if the soleus H-reflex was greater than (HRup mode) or less than (HRdown mode) a criterion or continued under the control condition (HRcon mode) in which the H-reflex was simply measured. We then measured axonal conduction velocity of triceps surae motor units of HRup, HRdown, and HRcon rats by stimulating the axon in the ventral root and recording from the tibial nerve. Conduction velocity was 8% less in successful HRdown rats than in HRcon rats (P=0.02). Conduction velocity in HRup rats and unsuccessful HRdown rats was not significantly different from that in HRcon rats. Since recording bypassed the intra-spinal portion of the motoneuron, the change was clearly in the axon. This decrease was similar to the 6% decrease previously found in successful HRdown monkeys. Unsuccessful HRdown rats and monkeys did not show this decrease. This result suggests that the mechanism of HRdown conditioning is similar in rats and monkeys and provides further support for the hypothesis that HRdown conditioning decreases motoneuron excitability by producing a positive shift in firing threshold. While traditional theories of learning emphasize synaptic plasticity, neuronal plasticity may also contribute to operantly conditioned behavioral changes.10aconduction velocity10aH-Reflex10amotoneuron10aplasticity10aSpinal Cord1 aCarp, Jonathan, S.1 aChen, Xiang Yang1 aSheikh, H.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/1120629001213nas a2200313   4500008004100000022001400041245005000055210004500105300001400150490000700164520043400171653001300605653001000618653001700628653002100645653001300666653001100679653001500690653001100705653001200716653001100728653001600739653001600755653002200771653001500793100002100808700002300829856004700852       1993                        eng d  a0065-140000aThe volitional nature of the simplest reflex.0 avolitional nature of the simplest reflex  a103–1110 v533 aRecent studies suggest that none of the behaviors of the vertebrate CNS are fixed responses incapable of change. Even the simplest reflex of all, the two-neuron, monosynaptic spinal stretch reflex (SSR), undergoes adaptive change under appropriate circumstances. Operantly conditioned SSR change occurs gradually over days and weeks and is associated with a complex pattern of CNS plasticity at both spinal and supraspinal sites.10abehavior10aBrain10aconditioning10ahuman physiology10aLearning10aMemory10amotoneuron10anature10aprimate10aReflex10aSpinal Cord10aspinal site10asupra spinal site10avertebrate1 aWolpaw, Jonathan1 aCarp, Jonathan, S.  uhttp://www.ncbi.nlm.nih.gov/pubmed/831723801216nas a2200229   4500008004100000022001400041245006700055210006600122260001200188300001400200490000700214520057800221653001600799653001500815653001500830653002100845653000800866100002100874700002300895700002100918856004700939       1992                        eng d  a0014-481900aConstancy of motor axon conduction time during growth in rats.0 aConstancy of motor axon conduction time during growth in rats  c08/1992  a343–3450 v903 aAxon conduction distance, conduction velocity, and conduction time were measured for individual triceps surae motoneurons in Sprague-Dawley rats weighing 230-630 g (i.e., age range 6-16 weeks). Both conduction distance (nerve length) and velocity were closely correlated with weight (r = 0.95 and r = 0.82, respectively). In contrast, conduction time did not change as weight increased nearly threefold. This striking constancy is probably due to a corresponding increase in axon diameter. It could contribute to maintenance of stable motor performance during rapid growth.10adevelopment10amotoneuron10amotor axon10anerve conduction10arat1 aChen, Xiang Yang1 aCarp, Jonathan, S.1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/139714801769nas a2200253   4500008004100000022001400041245010600055210006900161260001200230300001400242490000800256520104100264653001701305653001301322653001101335653001501346653001701361653001201378653001801390100002101408700002301429700001601452856004701468       1989                        eng d  a0304-394000aMemory traces in spinal cord produced by H-reflex conditioning: effects of post-tetanic potentiation.0 aMemory traces in spinal cord produced by Hreflex conditioning ef  c08/1989  a113–1190 v1033 aOperant conditioning of the wholly spinal, largely monosynaptic triceps surae H-reflex in monkeys causes changes in lumbosacral spinal cord that persist after removal of supraspinal influence. We evaluated the interaction between post-tetanic potentiation and these memory traces. Animals in which the triceps surae H-reflex in one leg had been increased or decreased by conditioning were deeply anesthetized, and monosynaptic reflexes to L6-S1 dorsal root stimulation were recorded before and after tetanization from both legs for 3 days after thoracic cord transection. Animals remained anesthetized throughout and were sacrificed by overdose. Reflex asymmetries consistent with the effect of H-reflex conditioning were present after transection and persisted through the 3 days of study. Tetanization affected conditioned leg and control leg reflexes similarly. This finding suggests that, while post-tetanic potentiation and probably H-reflex conditioning alter Ia synaptic transmission, the two phenomena have different mechanisms.10aconditioning10aLearning10aMemory10amotoneuron10apotentiation10aprimate10aspinal reflex1 aWolpaw, Jonathan1 aCarp, Jonathan, S.1 aLee, C., L.  uhttp://www.ncbi.nlm.nih.gov/pubmed/2779852