Models of the gaze orienting system: a brief survey

This chapter reviews current ideas on the neural control of eye and head movements, with special emphasis on the role of the superior colliculus. The problem of how gaze shifts are controlled has too many aspects to be grasped in a single model, and it is therefore not yet possible to develop a model that does justice to the complexity of the neural control system and which can account for its rich repertoire of capabilities. A more realistic approach is to concentrate on a few well-studied aspects of system behavior that can be isolated as challenges for a much more limited endeavour. The models discussed here concentrate on the role and the neural implementation of internal feedback, the transformation from topographically to temporally coded signals (and vice versa), the neural implementation of Listing's law, and the collicular role in the co-ordination of combined eye–head movements. Although each of these models concentrates on a particular set of aspects of the total problem and ignores others, taken together they can serve to illustrate how the signal processing at various levels in the saccadic control system can be viewed from different angles, and to clarify the issues surrounding the collicular role in the control of gaze. Before these models can be discussed, we will have to review earlier relevant models.