Abstract
To perceive geometric properties of external objects, the visual system must map their physical relations onto intrinsic, non-isomorphic neural representations. This mapping can be modified by adaptation: exposure to a texture reduces the perceived separation between objects (Hisakata, Nishida, & Johnston, 2016). Here we investigated the spatial reach of this effect. After presentation of an adaptor (a dynamic irregular grid of black and white dots), in either the left or right visual field, two pairs of dots appeared on either side of the fixation: a standard (1 dva separation) and a test pair (variable separation). Participants reported which pair appeared to have a greater inter-dot separation. To test the spatial tuning of the effect, the position of the standard relative to the adaptor varied. When presented in the adapted region, the standard appeared compressed by ~30%. The compression decreased (~10%) when the dots straddled the adaptor’s edge, and disappeared when the standard and adaptor were not-overlapping, suggesting a narrow tuning of the compression effect. To test whether the compression occurs in retinotopic or world-centered coordinates, participants shifted their gaze after the adaptation to an intermediate, and then to a final, test location. This allowed us to present the standard at either the same retinal or screen coordinates as the adaptor. Performance was compared to conditions where gaze remained fixed across adaptation and test periods, and the standard was presented either at adapted (full adaptation) or non-adapted (control) locations. We found evidence for both retinotopic and world-centered transfer of the distance compression, albeit with reduced magnitude (~50% and 70% relative to the full adaptation condition, respectively). The results suggest that mechanisms transforming external geometrical properties to neural representations can at least partly compensate for differences between retinal images and object positions in the external world induced by eye movements.