Landmarks Reduce But Not Eliminate Gaze-Dependent Errors in Memory-Guided Reaching I Schütz1, D Y Henriques2, K Fiehler1 |
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1Experimental Psychology, Justus-Liebig-University Giessen, Germany |
| Previous studies suggest that the brain codes and updates the locations of remembered visual targets relative to gaze. In an earlier study, we showed that this was true for both immediate and delayed movements, at least when no other visual cues are present [Fiehler, Schütz and Henriques, 2011, Vision Research, 51(8), 890-897]. The present study investigated whether additional cues from stable visual landmarks influence gaze-dependent spatial updating of reach targets. If the brain uses a purely gaze-dependent representation to encode and update remembered target locations, we expect no differences in gaze-dependent reaching errors with or without landmarks. However, if an allocentric or a combination of both allocentric and gaze-dependent representations is used, we expect reduced or no gaze-dependent errors. Subjects foveated visual targets, then shifted gaze to an eccentric fixation position before they reached for the remembered target either immediately or after a delay of up to 12 seconds. In the landmark condition, vertical light tubes to both sides of the stimulus display served as landmarks. Reach errors varied with current gaze direction regardless of landmark availability and delay. With landmarks present, the gaze-dependent pattern was significantly reduced, suggesting a combination of ego- and allocentric representations. |
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