The perception of suprathreshold contrast and fast adaptive filtering

Bex, Peter J.; Langley, Keith

doi:10.1167/7.12.1

Cited by 59 publications

(56 citation statements)

References 71 publications

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“…Early studies found that apparent contrast did not depend on spatial and temporal frequencies of luminance modulation: a phenomenon called “contrast constancy” (Georgeson & Sullivan, 1975; Georgeson, 1987; Webster, Georgeson, & Webster, 2002). Recent studies contested this conclusion, however, and found that apparent contrast did vary across spatiotemporal frequencies, reflecting the perception near threshold (Bex & Langley, 2007; Smith, 2015). Our finding that perception of suprathreshold stimuli varies across spatiotemporal stimuli agrees with the observations of failure of contrast constancy.…”

Section: Discussionmentioning

confidence: 99%

Paradoxical perception of object identity in visual motion

2017

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In the course of perceptual organization, incomplete optical stimulation can evoke the experience of complete objects with distinct perceptual identities. According to a well-known principle of perceptual organization, stimulus parts separated by shorter spatial distances are more likely to appear as parts of the same perceptual identity. Whereas this principle of proximity has been confirmed in many studies of perceptual grouping in static displays, we show that it does not generalize to perception of object identity in dynamic displays, where the parts are separated by spatial and temporal distances. We use ambiguous displays which contain multiple moving parts and which can be perceived two ways: as two large objects that gradually change their size or as multiple smaller objects that rotate independent of one another. Grouping over long and short distances corresponds to the perception of the respectively large and small objects. We find that grouping over long distances is often preferred to grouping over short distances, against predictions of the proximity principle. Even though these effects are observed at high luminance contrast, we show that they are consistent with results obtained at the threshold of luminance contrast, in agreement with predictions of a theory of efficient motion measurement. This is evidence that the perception of object identity can be explained by a principle of neural economy rather than by the empirical principle of proximity.

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Section: Discussionmentioning

confidence: 99%

Paradoxical perception of object identity in visual motion

2017

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“…Similar gap effect has been found by many other studies (Schiller et al, 1987; Munoz et al, 1998; Bucci et al, 2005; Yang and Kapoula, 2006; Yang et al, 2006). This result can be explained by the release of the fixation in the gap task; competition between the two points (central versus peripheral) leads to a latency increase in the overlap task (Dorris et al, 1997; Rolfs and Vitu, 2007). Advanced motor preparation in the gap task is another mechanism (Rolfs and Vitu, 2007; Vernet et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Latencies are 40–110 ms shorter in the gap task. This effect called “gap effect” (Saslow, 1967) is believed to be related to advance movement preparation due to release of the oculomotor fixation in the gap task (Rolfs and Vitu, 2007). It is believed that in the gap task, saccade initiation is triggered by the posterior parietal cortex (PPC; Pierrot-Deseilligny et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Different Effects of Double-Pulse TMS of the Posterior Parietal Cortex on Reflexive and Voluntary Saccades

Kapoula¹,

Yang²,

Sabbah³

2011

Front. Hum. Neurosci.

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Gap and overlap tasks are widely used to promote automatic versus controlled saccades. This study examines the hypothesis that the right posterior parietal cortex (PPC) is differently involved in the two tasks. Twelve healthy students participated in the experiment. We used double-pulse transcranial magnetic stimulation (dTMS) on the right PPC, the first pulse delivered at the target onset and the second 65 or 80 ms later. Each subject performed several blocks of gap or overlap task with or without dTMS. Eye movements were recorded with an Eyelink device. The results show an increase of latency of saccades after dTMS of the right PPC for both tasks but for different time windows (0–80 ms for the gap task, 0–65 ms for the overlap task). Moreover, for rightward saccades the coefficient of variation of latency increased in the gap task but decreased in the overlap task. Finally, in the gap task and for leftward saccades only, dTMS at 0–80 ms decreased the amplitude and the speed of saccades. Although the study is preliminary and needs further investigation in detail, the results support the hypothesis that the right PPC is involved differently in the initiation of the saccades for the two tasks: in the gap task the PPC controls saccade triggering while in the overlap task it could be a relay to the Frontal Eye Fields which is known to control voluntary saccades, e.g., memory-guided and perhaps the controlled saccades in the overlap task The results have theoretical and clinical significance as gap-overlap tasks are easy to perform even in advanced age and in patients with neurodegenerative diseases.

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“…Whenever a stimulus property was found to influence the probability of perceptual dominance during BR it was added to a grab bag of characteristics collectively termed signal strength. However, close inspection of this grab bag reveals that many features within it could be used to differentiate images of selective obstructions from images of more distant objects (see Fahle, 1982a,b; Arnold et al, 2007; Changizi and Shimojo, 2008). …”

Section: Signal Strengthmentioning

confidence: 99%

“…Similarly, blurring an image reduces image contrast (Fahle, 1982a,b), and both luminance and chromatic contrasts contribute to signal strength (Levelt, 1968; Mueller and Blake, 1989; Kovacs et al, 1996; Pearson and Clifford, 2004). Clearly signal strength, or at least a number of characteristics grouped under this term, would be useful for a process that strives to suppress awareness of selective obstructions in order to enhance the visibility of more distant objects (Fahle, 1982a,b; Arnold et al, 2007; Changizi and Shimojo, 2008). So another reason BR is uncommon is that the images of selective obstructions have a very low signal strength.…”

Section: Signal Strengthmentioning

confidence: 99%

Why is Binocular Rivalry Uncommon? Discrepant Monocular Images in the Real World

Arnold¹

2011

Front. Hum. Neurosci.

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When different images project to corresponding points in the two eyes they can instigate a phenomenon called binocular rivalry (BR), wherein each image seems to intermittently disappear such that only one of the two images is seen at a time. Cautious readers may have noted an important caveat in the opening sentence – this situation can instigate BR, but usually it doesn’t. Unmatched monocular images are frequently encountered in daily life due to either differential occlusions of the two eyes or because of selective obstructions of just one eye, but this does not tend to induce BR. Here I will explore the reasons for this and discuss implications for BR in general. It will be argued that BR is resolved in favor of the instantaneously stronger neural signal, and that this process is driven by an adaptation that enhances the visibility of distant fixated objects over that of more proximate obstructions of an eye. Accordingly, BR would reflect the dynamics of an inherently visual operation that usually deals with real-world constraints.

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The perception of suprathreshold contrast and fast adaptive filtering

Cited by 59 publications

References 71 publications

Paradoxical perception of object identity in visual motion

Paradoxical perception of object identity in visual motion

Different Effects of Double-Pulse TMS of the Posterior Parietal Cortex on Reflexive and Voluntary Saccades

Why is Binocular Rivalry Uncommon? Discrepant Monocular Images in the Real World

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