Abstract
This experiment investigates the interaction between the perceptual representations of the same or different letters presented at variable distances within the visual field. To assess the strengths of these representations, we used the encoding-related lateralization method (ERL, Gratton, 1998). With this method, perceptual representations are induced by flashing several items to the left or right fixation, and are subsequently tested by a foveally-presented test item that may or may not match one of the studied items. A matching test item elicits an ERP response that is lateralized depending on the side of the previously presented stimulus. We have previously shown (Shin et al., in press) that the ERP response is characterized by a series of deflections reflecting the reactivation of progressively more complex perceptual representations. One of these deflections, with a latency of 400–600 ms from stimulation, reflects the reactivation of a form of perceptual representation that includes a relational representation among different stimuli. Here we investigated whether this relational representation is affected by the relative distance between stimuli in the visual field (close or far) as well as their identity (same or different letters). Our data showed: (1) different behavioral responses between the same vs. different and close vs. far conditions, (2) larger ERL at a latency of 400–600 ms for the far/same condition than for the other three conditions. These results suggest that the long-latency ERL effect reflects a form of perceptual representation that is degraded by either contiguity or feature conflict between stimuli.