Spinal and supraspinal effects of long-term stimulation of sensorimotor cortex in rats.
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.
Chen
Xiang Yang
XY
Laboratory of Nervous System Disorders, Wadsworth Center, New York State Department of Health, Albany, New York 12201-0509, USA. chenx@wadsworth.org
Pillai
Shreejith
S
Chen
Yi
Y
Wang
Yu
Y
Chen
Lu
L
Carp
Jonathan S
JS
Wolpaw
Jonathan R
JR
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