Updating of an occluded moving target for interceptive saccades.

Editor's Note: These short, critical reviews of recent papers in the Journal, written exclusively by graduate students or postdoctoral fellows, are intended to summarize the important findings of the paper and provide additional insight and commentary. For more information on the format and purpose of the Journal Club, please see Review of Fleuriet and Goffart In daily life, many objects of interest move relative to our bodies. Adequate perception of such objects involves keeping them foveated through coordinated saccadic and pursuit eye movements. If an object moves in the visual periphery it can only be pursued after an interceptive saccade, which brings the object's image onto the fovea. These interceptive saccades are generally accurate, even if they occur during occlusion (Bennett and Barnes, 2006). This indicates that the brain accounts for the continuous displacement of a moving target. Although much is known about the brain mechanisms underlying eye movements , the specifics of how the brain achieves accurate interceptive saccades are still debated. One of these debates centers on how the oculomotor system accounts for target displacement resulting from motion when planning saccades. According to one view, the saccade generator incorporates two distinct drives: a position signal within the superior colliculus (SC) relaying target position, and an extracolicular motion-based signal accounting for subsequent target displacement (Keller et al. These signals are postulated to converge on premotor neu-rons in the brainstem. This " dual-drive " scheme was proposed based on the observation that SC activity during interceptive sac-cades does not reflect target position at saccade end and that the kinematics of inter-ceptive saccades differ from those of sac-cades to stationary targets (Keller et al., 1996; Guan et al., 2005). An alternative view suggests that motion compensation occurs within or upstream to the SC, which keeps track of the expected target position (Fleu-riet et al., 2011). In this " remapping " scheme, saccades to stationary and moving targets could then be accomplished using the same feedback mechanism. A motion-based prediction of target displacement has in fact been observed in activity of the frontal eye fields (FEF) (Xiao et al., 2007; Cas-sanello et al., 2008; Ferrera and Barborica, 2010), which projects to SC. In barn owls, activity within the auditory map in the tec-tum (the homolog of SC in monkeys) also codes a position ahead of the moving sound that gave rise to the activity (Witten et al., 2006). A recent study published …