Different computations underlie overt and covert spatial attention

Abstract

Perception and action are tightly coupled: visual responses at the saccade target are enhanced right before saccade onset. This phenomenon, presaccadic attention, is a form of overt attention—deployment of visual attention with concurrent eye movements. Presaccadic attention is well-documented, but its underlying computational process remains unknown. This is in stark contrast with covert attention—deployment of visual attention without concurrent eye movements—for which the computational process is well characterized. Here, a series of psychophysical experiments reveal that presaccadic attention modulates visual performance only via response gain changes even when attention field size increases, violating the predictions of a normalization model of attention, which has been widely used to explain the computations underlying covert attention. Our empirical results and model comparisons reveal that the perceptual modulations by overt and covert spatial attention are mediated through different computations.

Visual Perception: Attending beyond the Eyes’ Reach

“…To conclude, the focal article examining a special population [3], together with studies investigating neurotypical participants, provides converging evidence that covert attention is possible in the absence of eye movement planning [15][16][17][18], and beyond the oculomotor range [10,11]. These studies are in accordance with several models of covert attention that are independent of eye movement planning (e.g., [20]).…”

“…Crucially, these presaccadic effects are not present with covert attention [15][16][17]. Moreover, although both covert attention and presaccadic attention increase contrast sensitivity, their behavioral effects and underlying computations differ [18].…”

“…Visual sensitivity is a more direct and interpretable behavioral correlate of attention (as used in many studies; e.g., [1,10,[13][14][15][16][17][18]) than response times because detection-, decision-and response-dependent processes cannot be disentangled in the latter case. The authors experimentally limited the range of eye movements using a head rotation protocol that prevents performing large saccades against the rotation direction (Figure 1C).…”

“…To further compare and contrast overt and covert attention, recent studies in the Carrasco (co-author here) lab [15][16][17][18] have explored how presaccadic attention improves performance [10,[13][14][15][16][17][18][19] and concurrently modulates the representation of featural information [15][16][17][18]. They have found increased selectivity (sharpened orientation tuning [16]) and enhanced spatial resolution (shifting spatial frequency tuning toward higher frequencies [16,17]), which facilitate information processing at the upcoming eye landing location.…”