Explicit Attention to Allocentric Landmarks Improves Memory-Guided Reaching

The presence of an allocentric landmark can have both explicit (instruction-dependent) and implicit influences on reaching performance However, it is not known how the instruction itself (to rely either on egocentric versus allocentric cues) influences memory-guided reaching. Here, 13 participants performed a task with two instruction conditions (egocentric vs. allocentric), but with similar sensory and motor conditions. In the allocentric condition, participants were instructed to remember the initial location of the target relative to a landmark, and to reach relative to a shifted landmark. In the egocentric condition, participants were instructed to ignore the landmark and point toward the remembered location of the target. The allocentric instructions yielded significantly more accurate pointing than the egocentric instruction, despite identical visual and motor conditions and regardless of the final pointing side. This suggests that explicit attention to a visual landmark better recruits allocentric coding mechanisms that can augment implicit egocentric visuomotor transformations.