Abstract
Efficient control of attentional resources and high-acuity vision are both fundamental for survival. Shifts in visual attention are known to covertly enhance processing at locations away from the center of gaze, where visual resolution is low. It is unknown, however, whether selective spatial attention operates where the observer is already looking—that is, within the high-acuity foveola, the small yet disproportionally important rod-free region of the retina. Using new methods for precisely controlling retinal stimulation, here we show that covert attention flexibly improves and speeds up both detection and discrimination at loci only a fraction of a degree apart within the foveola. These findings reveal a surprisingly precise control of attention and its involvement in fine spatial vision. They show that the commonly studied covert shifts of attention away from the fovea are the expression of a global mechanism that exerts its action across the entire visual field.
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Acknowledgements
This work was supported by National Science Foundation grants BCS-1534932 (M.P.) and 1420212 (M.R.), and National Institutes of Health grants R01-EY18363 (M.R.), R01-EY019693 (M.C) and R01-EY016200 (M.C). We thank M. Landy, S. Ling, E. Niebur, M. Spering, J. Victor, A. White and Y. Yeshurun for comments and R. Ezzo for helping with data collection.
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M.P. conceived the study and collected and analyzed the data. The three authors contributed to the design of the experiments, the interpretation of experimental data, and the writing of the manuscript.
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Integrated supplementary information
Supplementary Figure 1 Velocity of eye movements.
Data represent averages across observers (n=5) for the cue-target intervals of Experiment 1 (parafovea; Fig. 1) and 2 (foveola; Fig. 2). In Experiment 2, stimuli were stabilized on the retina. (A) Average polar histograms of ocular drift velocity. (B) Mean instantaneous speed of ocular drift. Similar speed values were measured in the two experiments (p=0.63; two-tailed paired t-test). Error bars represent s.e.m. Time t=0 marks cue onset.
Supplementary Figure 2 Comparison between manual and oculomotor reaction times with stimuli in the parafovea and in the foveola.
The two sets of data on the left (Manual) refer to the neutral trials of the detection experiments of Fig. 1 (parafovea; red) and Fig. 2 (foveola; blue). In these experiments, the observer reported the appearance of the target by pressing a button. For comparison, data points on the right (Saccade) show oculomotor reaction times in the neutral trials of similar experiments, but in which the target was reported by performing a saccade toward its location rather than by pressing a button. Reaction times are measured relative to target’s offset. Error bars are s.e.m. (n=4).
Supplementary Figure 3 Fine attentional control during normal retinal image motion (drift-only trials).
Means ± s.e.m. for two individual subjects who were run extensively in Experiment 4 to collect sufficient numbers of trials without microsaccades (percentages of trials with microsaccades: 34%). Both subjects continued to exhibit significant differences between valid and invalid trials in both sensitivity (p<0.05, two-tailed z-test) and reaction times (p<0.05, ranksum test).
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Poletti, M., Rucci, M. & Carrasco, M. Selective attention within the foveola. Nat Neurosci 20, 1413–1417 (2017). https://doi.org/10.1038/nn.4622
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DOI: https://doi.org/10.1038/nn.4622
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