Figure 2. The effects of presaccadic and covert attention on featural representations.

(A) In psychophysical experiments, participants were required to detect a grating at a fixed orientation (represented by 0° in the figure), and a reverse correlation technique was used to characterize the orientation tuning employed by the visual system. Presaccadic attention increases the gain and reduces the width of orientation tuning [18,50]. Adapted from [18]. (B-C) Covert endogenous and exogenous attention only increase the gain [51–55]. Adapted from [55]. (D-F) Presaccadic attention [18,47] and covert exogenous attention preferentially increase the sensitivity of high-SF information by shifting the SF tuning curve rightward [55,58,59,64]. whereas covert endogenous attention enhances a broad range of SFs uniformly [55,62–64]. The dashed vertical lines indicate the peak of the tuning functions. See details of the experimental protocols in BOX 1. (D) adapted from [18]. (E) and (F) adapted from [55]. (G-I) Subjective contrast appearance of visual stimuli can be estimated by measuring the point of subjective equality (PSE) in tasks requiring participants to compare the contrast of two stimuli. In the experiments, the contrast of a test stimulus typically varies across trials while the contrast of a standard stimulus is fixed. Here, the percentage of trials in which participants judge the test stimulus to have a higher contrast than the standard (y-axis) is plotted against the contrast of the test stimulus (x-axis). The orange curves represent the condition in which the test stimulus is cued (attended). Both presaccadic attention [15] as well as endogenous [74] and exogenous [66–71] covert attention enhance perceived contrast. The enhancement by presaccadic attention exhibits a gradual trend right before saccade onset (inset in G, adapted from [15]). (H) adapted from [65]. (I) adapted from [66].