Saccadic and perceptual performance in visual search tasks I Contrast detection and discrimination

Beutter, Brent R.; Eckstein, Miguel P.; Stone, Leland S.

doi:10.1364/josaa.20.001341

Cited by 69 publications

(78 citation statements)

References 47 publications

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“…Second, saccades do not always take into account the foveal and peripheral discriminability of potential targets in a search display (55). Third, the efficiency of saccadic decisions is well below the perceptual efficiency because saccades are programmed even before all available information has been integrated (56). Here we show that this lack of optimization holds not only for visual signals but even more for value information that takes longer to become available.…”

Section: Discussionmentioning

confidence: 72%

Dynamic integration of information about salience and value for saccadic eye movements

Schütz

Trommershäuser

Gegenfurtner

2012

Proc. Natl. Acad. Sci. U.S.A.

134

117

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Humans shift their gaze to a new location several times per second. It is still unclear what determines where they look next. Fixation behavior is influenced by the low-level salience of the visual stimulus, such as luminance, contrast, and color, but also by highlevel task demands and prior knowledge. Under natural conditions, different sources of information might conflict with each other and have to be combined. In our paradigm, we trade off visual salience against expected value. We show that both salience and value information influence the saccadic end point within an object, but with different time courses. The relative weights of salience and value are not constant but vary from eye movement to eye movement, depending critically on the availability of the value information at the time when the saccade is programmed. Shortlatency saccades are determined mainly by salience, but value information is taken into account for long-latency saccades. We present a model that describes these data by dynamically weighting and integrating detailed topographic maps of visual salience and value. These results support the notion of independent neural pathways for the processing of visual information and value.neuroeconomics | decision-making | cue combination | visual perception B ecause of foveal specialization for high acuity and color vision, humans frequently move their eyes to project different parts of the visual scene on the fovea. Although the basic networks for the programming and execution of saccades have been studied for decades (1, 2), surprisingly little is known about the neural processes that underlie selection of the point of fixation of the next saccade. To some degree, the weighted combination of basic visual-stimulus features can predict saccadic eye movements in natural scenes (3-5). These basic stimulus features are, among others, local differences in luminance, color, or orientation and are combined by the visual system in a bottom-up image-based salience map. However, the salience difference between fixated and nonfixated image locations is typically rather small (6, 7), indicating that the influence of salience may be modulated by other factors. Visual salience, by definition, is determined by features of the visual scene alone and therefore is determined exclusively by visual bottom-up processing. Other factors reflect the influence of top-down processing. Task demands, for example, exhibit constraints on gaze patterns in different activities such as visual searching (8), manipulating an object (9), playing ball sports, preparing a cup of tea (10), and navigating between obstacles (11). In all these examples, gaze is concentrated on objects that are relevant for the task.Along different lines, recent research in neuroeconomics has used saccadic eye movements as a tool to uncover the neural bases of primate choice behavior. The results of these experiments indicate that value can be an important determinant of the neural activity underlying the selection of a saccadic target when one object bear...

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Section: Discussionmentioning

confidence: 72%

Dynamic integration of information about salience and value for saccadic eye movements

Schütz

Trommershäuser

Gegenfurtner

2012

Proc. Natl. Acad. Sci. U.S.A.

134

117

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“…For peripheral selection, observers could monitor peripheral mechanisms tuned to vertical orientations that scale their response with pattern contrast. The eye movement decision may be based on integrating and comparing mechanisms that represent different locations in the visual field, with the saccade target being the location that triggered the maximum integrated response (46,47).…”

Section: Discussionmentioning

confidence: 99%

Foveal analysis and peripheral selection during active visual sampling

Ludwig

Davies

Eckstein

2014

Proc. Natl. Acad. Sci. U.S.A.

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Human vision is an active process in which information is sampled during brief periods of stable fixation in between gaze shifts. Foveal analysis serves to identify the currently fixated object and has to be coordinated with a peripheral selection process of the next fixation location. Models of visual search and scene perception typically focus on the latter, without considering foveal processing requirements. We developed a dual-task noise classification technique that enables identification of the information uptake for foveal analysis and peripheral selection within a single fixation. Human observers had to use foveal vision to extract visual feature information (orientation) from different locations for a psychophysical comparison. The selection of to-be-fixated locations was guided by a different feature (luminance contrast). We inserted noise in both visual features and identified the uptake of information by looking at correlations between the noise at different points in time and behavior. Our data show that foveal analysis and peripheral selection proceeded completely in parallel. Peripheral processing stopped some time before the onset of an eye movement, but foveal analysis continued during this period. Variations in the difficulty of foveal processing did not influence the uptake of peripheral information and the efficacy of peripheral selection, suggesting that foveal analysis and peripheral selection operated independently. These results provide important theoretical constraints on how to model target selection in conjunction with foveal object identification: in parallel and independently.A lmost all human visually guided behavior relies on the selective uptake of information, due to sensory and cognitive limitations. On the sensory side, the sampling of visual input by the retinal mosaic of photoreceptors becomes increasingly sparse and irregular away from central vision (1). In addition, fewer cortical neurons are devoted to the analysis of peripheral visual information (cortical magnification) (2, 3). Humans and other animals with so-called foveated visual systems have evolved gazeshifting mechanisms to overcome these limitations. Saccadic eye movements serve to rapidly and efficiently deploy gaze to objects and regions of interest in the visual field. Sampling the environment appropriately with gaze is the starting point of adaptive visual-motor behavior (4, 5).Studies have shown that saccadic eye movements are guided by analysis of information in the visual periphery up to 80-100 ms before saccade execution (6-8). However, active vision typically requires humans not only also to analyze information in the visual periphery to decide where to fixate next (peripheral selection), but also to analyze the information at the current fixation location (foveal analysis). Not much is known about how foveal analysis and peripheral selection are coordinated and interact. In this regard, we need to know (i) whether and to what extent foveal analysis and peripheral selection are constrained by a common bo...

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“…Thus, saccades were made without the benefit of visual feedback about localization accuracy (i.e., were open-loop), and we grossly matched the visual processing time and stimulus eccentricity for the motor and perceptual discriminations (Eckstein et al, 2001;Beutter et al, 2003). Observers were then asked to report whether the disk selected by the saccadic choice or the later test disk was brighter in a sequential two-interval forced-choice (2IFC) perceptual task, using a button press to indicate their perceptual choice.…”

Section: Methodsmentioning

confidence: 99%

“…The median saccadic latency across observers ranged from 179 to 309 ms, typical of normal, short-latency, ballistic saccades (Carpenter, 1981;Carpenter and Williams, 1995;Leigh and Zee, 2006). Using standard asymmetric probability and reward paradigms (see Materials and Methods), we shaped behavior by inducing a preference for one saccadic response, illustrated by the systematically shifted oculometric functions (Eckstein et al, 2001;Beutter et al, 2003) in Figure 3. This classic behavioral effect (Green and Swets, 1966;Terman and Terman, 1972;McCarthy and Davison, 1984) was significant in all cases ( p Ͻ 0.001, within-subject ANOVA), with similar results for the asymmetric-probability and asymmetricreward paradigms.…”

Section: Induced Motor Bias In Saccade Responsesmentioning

confidence: 99%

Effects of Prior Information and Reward on Oculomotor and Perceptual Choices

Liston

Stone²

2008

J. Neurosci.

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Expectations about the environment influence motor behavior. In simple tasks, for example, prior knowledge about which stimulus event will likely occur or which response will likely be rewarded induces a tendency to take the favored action (i.e., a motor or response bias), especially when sensory information is sparse or ambiguous. Models of choice behavior account for this bias by weighting decision alternatives unequally, either at an early sensory-input stage or at a downstream motor-output stage. These two alternatives can be distinguished empirically; the former predicts an altered percept that correlates with motor bias, the latter predicts no perceptual effect. By varying the prior probability of target or reward location, we induced biased oculomotor responses in a brightness selection task with human subjects. We found that the induced motor bias was correlated with an amplification of both the sensory signals and internal noise underlying brightness perception, without a systematic change in perceived overall brightness. We also found that the magnitude of the sensory amplification was correlated with the amount of noise in the brightness percept, consistent with a multiplicative weighting factor located downstream from the limiting internal sensory noise. Our data demonstrate that prior knowledge (about target location or reward) shapes visual signals for perception and action in parallel but does not improve the quality (i.e., signal-to-noise ratio) of sensory processing.

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Saccadic and perceptual performance in visual search tasks I Contrast detection and discrimination

Cited by 69 publications

References 47 publications

Dynamic integration of information about salience and value for saccadic eye movements

Dynamic integration of information about salience and value for saccadic eye movements

Foveal analysis and peripheral selection during active visual sampling

Effects of Prior Information and Reward on Oculomotor and Perceptual Choices

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