%0 Journal Article %J Journal of neurophysiology %D 2007 %T Spinal and supraspinal effects of long-term stimulation of sensorimotor cortex in rats. %A Xiang Yang Chen %A Pillai, Shreejith %A Yi Chen %A Wang, Yu %A Lu Chen %A Jonathan S. Carp %A Jonathan Wolpaw %K Time Factors %X Sensorimotor cortex (SMC) modifies spinal cord reflex function throughout life and is essential for operant conditioning of the H-reflex. To further explore this long-term SMC influence over spinal cord function and its possible clinical uses, we assessed the effect of long-term SMC stimulation on the soleus H-reflex. In freely moving rats, the soleus H-reflex was measured 24 h/day for 12 wk. The soleus background EMG and M response associated with H-reflex elicitation were kept stable throughout. SMC stimulation was delivered in a 20-day-on/20-day-off/20-day-on protocol in which a train of biphasic 1-ms pulses at 25 Hz for 1 s was delivered every 10 s for the on-days. The SMC stimulus was automatically adjusted to maintain a constant descending volley. H-reflex size gradually increased during the 20 on-days, stayed high during the 20 off-days, and rose further during the next 20 on-days. In addition, the SMC stimulus needed to maintain a stable descending volley rose steadily over days. It fell during the 20 off-days and rose again when stimulation resumed. These results suggest that SMC stimulation, like H-reflex operant conditioning, induces activity-dependent plasticity in both the brain and the spinal cord and that the plasticity responsible for the H-reflex increase persists longer after the end of SMC stimulation than that underlying the change in the SMC response to stimulation. %B Journal of neurophysiology %V 98 %P 878–887 %8 08/2007 %G eng %U http://www.ncbi.nlm.nih.gov/pubmed/17522179 %R 10.1152/jn.00283.2007