Distractor suppression operates in retinotopic coordinates

Our attention is influenced by past experiences, and recent studies have shown that people learn to extract statistical regularities in the environment resulting in attentional suppression of locations that are likely to contain a distractor. Here, we asked whether this suppression effect due to statistical learning operates in retinotopic (relative to the eyes) or spatiotopic (relative to the world) coordinates. In the current study, two circular displays were presented side by side. While fixating the center of one display, observers performed the additional singleton search task in which one location was more likely to contain a distractor. After searching for several trials in one display participants moved their eyes to the center of the other display and kept performing the additional singleton search task. Because of the saccadic eye movement to the other display, the suppressed location that in the previous display was in retinotopic coordinates became the spatiotopic location in the new display while the retinotopic location moved along with the eye movement in space. The results showed that, following the eye movement, the suppression remained in retinotopic coordinates, while there was no transfer of suppression to the spatiotopic coordinates. It is important to note that in the experiment conducted there were no environmental landmarks as the search displays were presented on a blank empty background. Also, the entire display shifted from side to side, making the whole visual field move along with the saccades. To address these limitations, a second experiment was conducted with a grid and placeholders in the display to enhance more environmental stability. The results however showed that even in a rich environment, attentional suppression still operated in retinotopic coordinates only. Given that suppression is only found in retinotopic coordinates, it is speculated that suppression maybe resolved by changing synaptic weights in early visual areas.