Trends in Neurosciences
Volume 44, Issue 8, August 2021, Pages 669-686
Journal home page for Trends in Neurosciences

Review
To look or not to look: dissociating presaccadic and covert spatial attention

https://doi.org/10.1016/j.tins.2021.05.002Get rights and content

Highlights

  • To effectively process visual information, individuals attend to relevant visual inputs by selectively processing information at some locations at the expense of information elsewhere. One can attend overtly, by making saccadic eye movements, or covertly, by prioritizing information without moving the eyes. Both processes improve visual performance, but have different temporal dynamics.

  • Behavioral evidence shows that covert spatial attention is not the consequence of oculomotor planning.

  • Presaccadic and covert exogenous (involuntary) and endogenous (voluntary) attention differentially alter the featural representation of basic dimensions – orientation and spatial frequency.

  • Different neural computations mediate the effects of presaccadic and covert attention on contrast sensitivity.

  • Partially overlapping brain areas underlie presaccadic and covert attention, but different neuronal populations within each area subserve each type of attention.

Attention is a central neural process that enables selective and efficient processing of visual information. Individuals can attend to specific visual information either overtly, by making an eye movement to an object of interest, or covertly, without moving their eyes. We review behavioral, neuropsychological, neurophysiological, and computational evidence of presaccadic attentional modulations that occur while preparing saccadic eye movements, and highlight their differences from those of covert spatial endogenous (voluntary) and exogenous (involuntary) attention. We discuss recent studies and experimental procedures on how these different types of attention impact visual performance, alter appearance, differentially modulate the featural representation of basic visual dimensions (orientation and spatial frequency), engage different neural computations, and recruit partially distinct neural substrates. We conclude that presaccadic attention and covert attention are dissociable.

Section snippets

Presaccadic and covert attention are dissociable

Much of human visual experience results from moving our gaze to actively explore the visual world and gather information. By scanning the scene with saccadic eye movements (see Glossary), we bring relevant objects into our fovea, where visual information is processed with high precision. The link between eye movements and visual perception is so tight that perception is already facilitated before our gaze has reached a location of interest: immediately before an eye movement, while we prepare

Linking saccadic eye movements and visual attention

Over the past three decades, different groups have found that perceptual judgments immediately before eye movement onset are more accurate for stimuli presented at the saccade target (the upcoming eye fixation) than elsewhere [5., 6., 7.]. Interest in the perceptual consequences of presaccadic attention has continuously increased, and numerous studies have explored its spatial and temporal properties using variations of a typical dual-task protocol (Table 1).

Spatial and temporal coupling of oculomotor planning and attentional orienting

By testing performance at different

Modulations of visual representations by presaccadic attention and covert attention

The vast majority of presaccadic attention research has focused on its effects on performance (e.g., accuracy in discrimination tasks). We discuss here recent advances that go beyond mere performance measures and reveal how presaccadic attention modulates featural representations – in other words the processing of visual features, including orientation, spatial frequency, and contrast. This assessment enables a differentiation of the cognitive, neural, and computational processes underlying

Common brain areas but distinct subpopulations

The tight coupling between eye movements and attentional orienting raises the question of whether presaccadic and covert spatial attention are based on the same neural processes. At a broad scale, the brain structures that are active during saccadic eye movements [the frontal eye fields (FEF), the precentral sulcus, and the superior colliculus (SC)] are also selectively modulated during covert attention tasks in human- and non-human primates [100., 101., 102., 103.]. Feedback signals projecting

Concluding remarks

Although both presaccadic attention and covert spatial attention enable selective processing of visual information and facilitate perception, there are clear dissociations in their temporal dynamics, modulations of featural representation of basic visual dimensions, neural computations, and neural correlates. Although questions remain about the specific origin, nature, and functional significance of presaccadic attention and covert attention, converging evidence indicates that the notion that

Acknowledgments

This research was supported by National Institutes of Health National Eye Institute grant R01 EY019693 to M.C. and a Feodor Lynen Research Fellowship from the Alexander von Humboldt Foundation to N.M.H. We thank Antoine Barbot, Antonio Fernández, Marc Himmelberg, Michael Jigo, and other members of the laboratory of M.C., as well as Luca Wollenberg and Heiner Deubel, for useful comments.

Declaration of interests

The authors declare no competing interests.

Glossary

Adaptation
reduced sensory responses to prolonged or repeated presentations of the same stimulus. In psychophysical experiments, visual performance for a test stimulus following an adaptor stimulus is lower when the stimuli share similar features (e.g., orientation).
Antisaccade task
participants are required to suppress a reflexive saccade to a salient visual stimulus and instead perform a voluntary saccade in the opposite direction.
Fovea
a depression in the inner retinal surface, ~1.5 mm in

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