Elimination of climbing fiber instructive signals during motor learning.

The climbing fiber input to the cerebellum from the inferior olive is thought to act as a teacher whose activity controls the induction of motor learning. We designed training conditions that did not elicit instructive signals in the climbing fibers, but nevertheless induced robust and consistent motor learning in the vestibulo-ocular reflex of rhesus monkeys. Our results indicate that instructive signals in the climbing fibers are not necessary for cerebellum-dependent learning. Instead, instructive signals carried by either the climbing fibers or Purkinje cell simple spikes may be sufficient to induce motor learning, with additive effects occurring when both instructive signals are present during training.