THE NERVOUS CONTROL OF GAZE ORIENTATION

This short paper presents and discusses some new findings and hypothes es in the field of saccadic gaze control. After a general introduction to the function of eye movements, the physiology of the deep layers o f the superior colliculus are reviewed. Recent experimental data sugge st the existence of an internal feedback of gaze velocity which update s this retinotopically organised map, in real time, during the executi on of the movement. This mechanism also permits a precise feedback con trol of such a fast movement, for which a classical external feedback is not possible, due to time delay. Another virtue of this spatially d istributed feedback is that it elegantly solves the spatio-temporal tr ansformation problem inherent to such a sensorimotor interface. Indeed , the visual input is topographically coded within its early processin g by the brain (place code), whereas the motor output is sequentially coded (time code). This hypothesis has been computer-modelled and simu lated. Further experimental data are however needed to confirm it.