Interactions between gaze-centered and allocentric representations of reach target location in the presence of spatial updating

Numerous studies have investigated the phenomenon of egocentric spatial updating in gaze-centered coordinates and some have studied the use of allocentric cues in visually-guided movement but it is not known how these two mechanisms Interact Here we tested whether gaze-centered and allocentric information combine at the time of viewing the target or if the brain waits until the last possible moment To do this we took advantage of the well-known fact that pointing and reaching movements show gaze-centered retinal magnification errors (RME) that update across saccades During gaze fixation we found that visual landmarks and hence allocentric information reduces RME for targets in the left visual hemifield but not in the right When a saccade was made between viewing and reaching this landmark-induced reduction in RME only depended on gaze at reach not at encoding Based on this finding we argue that egocentric-allocentric combination occurs after the intervening saccade This is consistent with previous findings in healthy and brain damaged subjects suggesting that the brain updates early spatial representations during eye movement and combines them at the time of action (C) 2010 Elsevier Ltd All rights reserved