TY - JOUR T1 - The complex structure of a simple memory. JF - Trends in neurosciences Y1 - 1997 A1 - Jonathan Wolpaw KW - H-Reflex KW - Learning KW - Memory KW - operant conditioning KW - plasticity KW - Spinal Cord KW - stretch reflex AB - Operant 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. VL - 20 UR - http://www.ncbi.nlm.nih.gov/pubmed/9416673 ER -