title: Spinal and supraspinal effects of long-term stimulation of sensorimotor cortex in rats.
abstract: 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.
authors.affiliation: Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA. chenx@wadsworth.org
authors.forename: Xiang Yang
authors.initials: XY
authors.lastname: Chen
authors.forename: Shreejith
authors.initials: S
authors.lastname: Pillai
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Lu
authors.initials: L
authors.lastname: Chen
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Carp
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Wolpaw
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D007839:Functional Laterality; D006181:H-Reflex / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D009475:Neurons, Afferent / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D013003:Somatosensory Cortex / Q000502:physiology* / Q000528:radiation effects; D013116:Spinal Cord / Q000502:physiology*; D013997:Time Factors