A study on chromatic contrast regulation

Harrar, Margalith; Viénot, Françoise

doi:10.1167/4.11.11

Cited by 28 publications

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“…A part of the results have been presented at previous conference. 30,31 The amount of chromatic contrast is derived from the l-value of the selected target considered as neutral by the observers. In figure 4, we can see that a remote peripheral color field generates a strong induction because the square that appears neutral to the observer, for example with a red peripheral field, is a reddish square.…”

Section: Resultsmentioning

confidence: 99%

Regulation of chromatic induction by neighboring images

Harrar

Viénot

2005

J. Opt. Soc. Am. A

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We deal with the regulation of chromatic contrast when the induction of a second stimulus (one of five neighboring surrounds) opposes the induction from a first stimulus (one of two remote vivid peripheral fields). Using a hue cancellation judgment, we show that, although every neighboring surround that we used has the same average chromatic content, the resulting color appearance of the target differs between surrounds, and this may be ascribed to the spatiochromatic organization of the surround. So, rather than the chromatic contrast amplitude or the frequential structure of the surround, it is the structure of proximity that matters.

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Section: Resultsmentioning

confidence: 99%

Regulation of chromatic induction by neighboring images

Harrar

Viénot

2005

J. Opt. Soc. Am. A

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Detection of small orientation changes and the precision of visual working memory

Salmela

Saarinen

2013

Vision Research

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We investigated the precision of orientation representations with two tasks, change detection and recall. Previously change detection has been measured only with relatively large orientation changes compared to psychophysical thresholds. In the first experiment, we measured the observers' ability (d') to detect small changes in orientation (5-30°) with 1-4 Gabor items. With one item even a 10° change was well detected (average d'=2.5). As the amount of change increased to 30°, the d' increased to 5.2. When the number of items was increased, the d's gradually decreased. In the second experiment, we used a recall task and the observers adjusted the orientation of a probe Gabor to match the orientation of a Gabor held in the memory. The standard deviation (s.d.) of errors was calculated from the Gaussian distribution fitted to the data. As the number of items increased from 1 to 6, the s.d. increased from 8.6° to 19.6°. Even with six items, the observers did not make any random adjustments. The results show a square root relation between the d'/s.d. and the number of items. The d' in change detection is directly proportional to the square root of (1/n) and the orientation change. The increase of the s.d. in recall task is inversely proportional to square root of (1/n). The results suggest that limited resources and precision of representations, without additional assumptions, determine the memory performance.

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The neural basis of precise visual short-term memory for complex recognisable objects

Veldsman

Mitchell

Cusack

2016

Preprint

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Recent evidence suggests that visual short-term memory (VSTM) capacity estimated using simple objects, such as colours and oriented bars, may not generalise well to more naturalistic stimuli. More visual detail can be stored in VSTM when complex, recognisable objects are maintained compared to simple objects. It is not yet known if it is recognisability that enhances memory precision, nor whether maintenance of recognisable objects is achieved with the same network of brain regions supporting maintenance of simple objects.We used a novel stimulus generation method to parametrically warp photographic images along a continuum, allowing separate estimation of the precision of memory representations and the number of items retained. The stimulus generation method was also designed to create unrecognisable, though perceptually matched, stimuli, to investigate the impact of recognisability on VSTM. We adapted the widely-used change detection and continuous report paradigms for use with complex, photographic images.Across three functional magnetic resonance imaging (fMRI) experiments, we demonstrated greater precision for recognisable objects in VSTM compared to unrecognisable objects. This clear behavioural advantage was not the result of recruitment of additional brain regions, or of stronger mean activity within the core network.Representational similarity analysis revealed greater variability across item repetitions in the representations of recognisable, compared to unrecognisable complex objects. We therefore propose that a richer range of neural representations support VSTM for complex recognisable objects.

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A study on chromatic contrast regulation

Cited by 28 publications

References 0 publications

Regulation of chromatic induction by neighboring images

Regulation of chromatic induction by neighboring images

Detection of small orientation changes and the precision of visual working memory

The neural basis of precise visual short-term memory for complex recognisable objects

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