Abstract
Although even fish can convert large-field visual motion into eye velocity, the ability to track a small object moving across rich visual environment is unique to the primates. This indicates that the generation of smooth pursuit eye movements requires a number of neural processes beyond simply transforming visual motion into eye motion. Those processes differentiate sensory-guided voluntary movements from reflexes.
Recent studies of smooth pursuit have shown that there are at least two different signal flows in this system; one converts visual motion into command of eye velocity, while the other regulates the strength of this conversion. The former process is likely shared with the visually-guided reflexive eye movements such as the optokinetic response and the ocular-following response. The latter may play roles in choosing a response to given visual inputs, maximizing the sensorimotor conversion for visual motion derived from a selected object or location. I will review recent stimulation experiments showing that the frontal eye fields (FEF) have access to both pursuit pathways, and that the FEF can regulate the gains of both the initiation and the maintenance of pursuit. Taken together with the results of other behavioral and recording studies, I will discuss possible signal flows through the FEF that regulate smooth pursuit eye movements. [Jpn J Physiol 54 Suppl:S35 (2004)]
