Immediate spatial distortions of pointing movements induced by visual landmarks.

Abstract

We tested the influence of two horizontally aligned visual landmarks on pointing movements to memorized targets, to investigate whether the visuomotor system can make use of an egocentric representation unaffected by visual context. The endpoints of pointing movements were systematically distorted toward the nearest visual landmark, indicating that spatial representations included both target and nontarget information. These distortions were not due to the presence of the landmarks during the movement but, rather, to their presence in the encoding phase. Qualitatively similar distortions were present even with the shortest possible retention phase, when the target was extinguished at movement onset. Finally, we found the same pattern of distortion when participants were forced to remember the target within an allocentric frame of reference. We argue that even early memory representations for pointing movements are influenced by visual information in the surrounding visual field.