01573nas a2200229   4500008004100000022001400041245004600055210004100101260001200142300001400154490000700168520098800175653001301163653001301176653001101189653002501200653001501225653001601240653001901256100002101275856004701296       1997                        eng d  a0166-223600aThe complex structure of a simple memory.0 acomplex structure of a simple memory  c12/1997  a588–5940 v203 aOperant conditioning of the vertebrate H-reflex, which appears to be closely related to learning that occurs in real life, is accompanied by plasticity at multiple sites. Change occurs in the firing threshold and conduction velocity of the motoneuron, in several different synaptic terminal populations on the motoneuron, and probably in interneurons as well. Change also occurs contralaterally. The corticospinal tract probably has an essential role in producing this plasticity. While certain of these changes, such as that in the firing threshold, are likely to contribute to the rewarded behavior (primary plasticity), others might preserve previously learned behaviors (compensatory plasticity), or are simply activity-driven products of change elsewhere (reactive plasticity). As these data and those from other simple vertebrate and invertebrate models indicate, a complex pattern of plasticity appears to be the necessary and inevitable outcome of even the simplest learning.10aH-Reflex10aLearning10aMemory10aoperant conditioning10aplasticity10aSpinal Cord10astretch reflex1 aWolpaw, Jonathan  uhttp://www.ncbi.nlm.nih.gov/pubmed/9416673