Studies of the neural basis of learning and memory in intact animals must, by their nature, start "from the top" by choosing a behavior that can be modified through learning, revealing how iaeuronal activity gives rise to that behavior, and then investigating, in the awake, behaving animal, changes in neural signaling that are associated with learning. Such studies also must recognize that the learning and memory expressed in the behavior of an animal will reflect both the properties of the neural network that mediates the behavior and the nature of the underlying changes in the operation of cells or synapses. In the past 10 years, there has been an explosion of information about learning and memory in the vestibulo-ocular reflex (VOR) of the awake, behaving monkey. At the same time, there have been unprecedented advances in understanding mechanisms of cellular plasticity such as long-term potentiation (LTP) in the hippocampus and long-term depression (LTD) in the cerebellum. A prerequisite for understanding learning and memory is to elevate specific mechanisms of cellular plasticity into cellular mechanisms of learning by establishing their function in the context of a neural system that mediates learning and memory in a particular behavior. Our review synthesizes the