Ablation of the inferior olive prevents H reflex down conditioning in rats.
We evaluated the role of the inferior olive (IO) in acquisition of the spinal cord plasticity that underlies H reflex down conditioning, a simple motor skill. The IO was chemically ablated before a 50 day exposure to an operant conditioning protocol that rewarded a smaller soleus H reflex. In normal rats, down conditioning succeeds (i.e. H reflex size decreases at least 20% in 80% of animals. Down conditioning failed in every IO ablated rat (P< 0.001 vs. normal rats) IO ablation itself had no long term effect on H reflex size. These results indicate that the IO is essential for acquisition of a down conditioned H reflex. With previous data, they support the hypothesis that IO and cortical inputs to cerebellum enable the cerebellum to guide sensorimotor cortex plasticity that produces and maintains the spinal cord plasticity that underlies the down conditioned H reflex. They help to further define H reflex conditioning as a model for understanding motor learning and as a new approach to enhancing functional recovery after trauma or disease.
Journal of neurophysiology