Robustness of the retinotopic attentional trace after eye movements

Abstract

With each eye movement, the image received by the visual system changes drastically. To maintain stable spatiotopic (world-centered) representations, the relevant retinotopic (eye-centered) coordinates must be continually updated. Although updating or remapping of visual scene representations can occur very rapidly, J. D. Golomb, M. M. Chun, and J. A. Mazer (2008) demonstrated that representations of sustained attention update more slowly than the remapping literature would predict; attentional benefits at previously attended retinotopic locations linger after completion of the saccade, even when this location is no longer behaviorally relevant. The present study explores the robustness of this "retinotopic attentional trace." We report significant retinotopic facilitation despite attempts to eliminate or reduce it by enhancing spatiotopic reference frames with permanent visual cues in the stimulus display and by introducing a different task where the attended location is the saccade target itself. Our results support and extend our earlier model of native retinotopically organized salience maps that must be dynamically updated to reflect the task-relevant spatiotopic location with each saccade. Consistent with the idea that attentional facilitation arises from persistent, recurrent neural activity, it takes measurable time for this facilitation to decay, leaving behind a retinotopic attentional trace after the saccade has been executed, regardless of conflicting task demands.

Figure 1

Task and conditions, Experiment 1. While subjects maintained fixation on the white fixation dot, a memory cue appeared briefly at another location. Subjects were instructed to hold this cued location in memory throughout the trial. The fixation dot then moved, and after completion of a saccade to the new fixation location, a probe stimulus (oriented bar) appeared after a variable delay in either the cue's spatiotopic (top), retinotopic (middle), or control (bottom) location. Subjects made a speeded button press response to indicate probe orientation. A memory test stimulus then appeared, and subjects indicated whether or not it occupied the same spatiotopic location as the memory cue. The light gray gridlines remained on the screen at all times to provide additional spatiotopic cues. The gray arrow depicting the saccade did not actually appear on the screen. Stimulus configuration illustrated here represents only one of several possible, counterbalanced cue-saccade configurations.

Figure 2

Task and conditions, Experiment 2. While subjects maintained fixation on the white fixation dot, a cue appeared briefly indicating the target of the upcoming saccade. Subjects were instructed to plan an eye movement to this location but not to execute the eye movement until the fixation dot disappeared. Once the fixation dot disappeared, subjects had 300 ms to accurately complete the memory-guided saccade. Upon completion of the saccade, the fixation dot reappeared in the new location, and a probe stimulus (oriented bar) later appeared after a variable delay in either the cue's spatiotopic (top), retinotopic (middle), or control (bottom) location. Subjects made a speeded button press response to indicate probe orientation. The gray arrow indicating the saccade did not actually appear on the screen. Stimulus configuration illustrated here represents only one of several possible counterbalanced cue-saccade configurations.

Figure 3

Attentional facilitation: Experiment 1. Attentional facilitation is plotted as the difference in RT for probes appearing in the spatiotopic and retinotopic locations compared to the control location baseline (zero). Positive values indicate attentional facilitation (RTs faster than at control locations). Data are plotted as a function of probe delay. Right panel illustrates sample probe locations for each experimental condition colored according to the plot legend on the left with black indicating the control location. White and gray dots indicate final and previous fixation locations, respectively; square indicates cued location, and arrow indicates saccade pattern. Error bars indicate standard error of the mean (SEM) after normalization to remove between-subject variability (Loftus & Masson, 1994); n = 20.

Figure 4

Attentional facilitation: Experiment 2. Attentional facilitation is plotted as the difference in RT for probes appearing at the retinotopic location of the cue compared to the control location baseline (zero). Positive values indicate attentional facilitation (RTs faster than at control locations). Data are plotted as a function of probe delay. Inset illustrates sample probe locations for each experimental condition with red indicating the retinotopic location, black indicating the control location and blue indicating the spatiotopic (current fixation) location. White and gray dots indicate final and previous fixation locations, respectively; square indicates cued location, and arrow indicates saccade pattern. Error bars are SEM after normalization to remove between-subject variability (Loftus & Masson, 1994); n = 20.