Effects of irreversible olivary system lesion on the gain adaptation of optokinetic response eye movement: a model based study

Abstract

The optokinetic reflex (OKR) is a behavioral oculomotor response which serves to stabilize moving images on the retina. As the cerebellum is intimately involved in the adaptive control of such compensatory eye movement, the OKR has been turned to a favorable test bed for modeling and assessing cerebellar learning function. Learning process in the cerebellum consists of two distinct phases: 1) short-term learning, which is acquired by single session of behavioral training and disappears within 24 hours, and 2) long-term learning which is induced by repeating sessions and persists for days. On the other hand, emerging evidences from experimental studies indicates high level of coordination between olivary system activity and cerebellar learning. However, it is still unclear which phase of learning will be affected by olivary system disruption. In this paper, we proposed a simple model for learning adaptation and memory formation of the cerebellum. The model is capable to reproduce the OKR gain adaptation of eye movement in both long and short term phases. The simulation results were found to strongly agree with previously reported experimental data from wild type mice. As a second step, we explore the effects of irreversible olivary system lesion on the gain adaptability of OKR by cutting off the connection of climbing fiber, which originates from the inferior olive (IO) neuron. Thereafter, comparing to the normal case, the gain of OKR undergoes a significant decline in both short and long phases of learning. This suggests that the olivary system plays a critical role in both short-and long-term adaption of OKR.