Modeling slow correcting gaze movements

Recent experimental results show evidence for the corrective role of postsaccadic drifts. This paper addresses the modeling of these slow correcting gaze movements (SCMs). Classical arguments to explain drifts are presented, both in the head fixed condition (pulse-step mismatch) and in the head free condition (vestibulo-ocular reflex (VOR)). The most significant behavioral and electrophysiological experimental data related to SCMs are then briefly reported, with the conclusion that SCMs have a clear corrective role, incompatible with classical explanations of drifts. Based on these experimental data, existing models of the saccadic system are then compared. A theoretical comparison of the classical Robinson model with an alternative model is proposed. Two possible (slow and fast) pathways involved in the control of SCMs are examined, and simulation results are presented. Finally, the discussion addresses the observed species differences in SCMs. The link between natural SCMs and electrical SC stimulations, and the interactions between saccades, VOR, and SCMs are also discussed.