Spatiotopic buildup of saccade target representation depends on target size

How we maintain spatial stability across saccade eye movements is an open question in visual neuroscience. A phenomenon that has received much attention in the field is our seemingly poor ability to discriminate the direction of transsaccadic target displacements. We have recently shown that discrimination performance increases the longer the saccade target has been previewed before saccade execution (Zimmermann, Morrone, & Burr, 2013). We have argued that the spatial representation of briefly presented stimuli is weak but that a strong representation is needed for transsaccadic, i.e., spatiotopic localization. Another factor that modulates the representation of saccade targets is stimulus size. The representation of spatially extended targets is more noisy than that of point-like targets. Here, I show that the increase in transsaccadic displacement discrimination as a function of saccade target preview duration depends on target size. This effect was found for spatially extended targets-thus replicating the results of Zimmermann et al. (2013)-but not for point-like targets. An analysis of saccade parameters revealed that the constant error for reaching the saccade target was bigger for spatially extended than for point-like targets, consistent with weaker representation of bigger targets. These results show that transsaccadic displacement discrimination becomes accurate when saccade targets are spatially extended and presented longer, thus resembling closer stimuli in real-world environments.