01909nas a2200181   4500008004100000022001400041245006900055210006600124260001200190300001400202490000800216520138400224653001701608100002101625700002101646700001301667856004701680       1994                        eng d  a0304-394000aOperant conditioning of primate H-reflex: phases of development.0 aOperant conditioning of primate Hreflex phases of development  c04/1994  a203–2070 v1703 aThis study sought to determine whether operantly conditioned change in the primate triceps surae (TS) H-reflex develops in distinct phases. Data from 20 animals in which the TS H-reflex in one leg was trained up (i.e., HRup mode) and 18 in which it was trained down (i.e., HRdown mode) were averaged to define H-reflex behavior in trained and control legs. In HRup animals, the trained-leg H-reflex showed a large phase I increase in the first two days followed by gradual phase II increase that continued for weeks. The control-leg H-reflex appeared to show much smaller phase I and phase II increases. In HRdown animals, the trained-leg H-reflex decreased gradually over weeks, while the control-leg H-reflex appeared to increase within 2 days and did not change from then on. The initial rapid increase in the HRdown control leg suggested that two early events occurred in the HRdown trained leg: a nonspecific increase like that in the control leg and an operantly conditioned mode-specific decrease. These two effects may have obscured each other, so that H-reflex size in the HRdown trained leg did not drop rapidly in the first few days. These results improve understanding of adaptive H-reflex change as an operantly conditioned phenomenon, and provide encouragement and direction for efforts to reproduce and study the phenomenon in reduced or anesthetized preparations.10aTime Factors1 aWolpaw, Jonathan1 aManiccia, D., M.1 aElia, T.  uhttp://www.ncbi.nlm.nih.gov/pubmed/8058188